Dissertations / Theses on the topic 'Photovoltaic power systems'
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Perez, de Larraya Espinosa Mikel. "Photovoltaic Power Plant Aging." Thesis, Högskolan i Gävle, Avdelningen för byggnadsteknik, energisystem och miljövetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-33252.
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One of the most pressing problems nowadays is climate change and global warming. As it name indicates, it is a problem that concerns the whole earth. There is no doubt that the main cause for this to happen is human, and very related to non-renewable carbon-based energy resources. However, technology has evolved, and some alternatives have appeared in the energy conversion sector. Nevertheless, they are relatively young yet. Since the growth in renewable energies technologies wind power and PV are the ones that have taken the lead. Wind power is a relatively mature technology and even if it still has challenges to overcome the horizon is clear. However, in the PV case the technology is more recent. Even if it is true that PV modules have been used in space applications for more than 60 years, large scale production has not begun until last 10 years. This leaves the uncertainty of how will PV plants and modules age. The author will try to analyse the aging of a specific 63 kWp PV plant located in the roof of a building in Gävle, monitoring production and ambient condition data, to estimate the degradation and the new nominal power of the plant. It has been found out that the degradation of the system is not considerable. PV modules and solar inverters were studied, and even if there are more elements in the system, those are the principal ones. PV modules suffered a degradation of less than 5%, while solar inverters’ efficiency dropped from 95,4% to around 93%.
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Tesfahunegn, Samson Gebre. "Fuel Cell Assisted PhotoVoltaic Power Systems." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-16942.
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Distributed generation (DG) systems as local power sources have great potential to contribute toward energy sustainability, energy efficiency and supply reliability. This thesis deals with DGs that use solar as primary energy input, hydrogen energy storage and conversion technologies (fuel cells and water electrolyzers) as long term backup and energy storage batteries and supercapacitors as short term backup. Standalone power systems isolated from the grid such as those used to power remote area off-grid loads and grid connected systems running in parallel with the main utility grid or a microgrid for local grid support are treated. As cost is the key challenge to the implementation of PV-hydrogen DGs, the main focus is developing sound control methods and operating strategies to help expedite their viability in the near future. The first part of the thesis deals with modeling of system components such as PV generator, fuel cell, lead acid/Li-ion storage batteries, electrolyzer, supercapacitor, power electronic converters and auxiliaries such as hydrogen storage tank and gas compressor. The subsystems are modeled as masked blocks with connectable terminals in Matlab®/Simulink® enabling easy interconnection with other subsystems. The models of main subsystems are fully/partially validated using measurement data or data obtained from data sheets and literature. The second part deals with control and operating strategies in PV hybrid standalone power systems. The models developed in the first part are used to simulate integrated systems. An attempt is made to provide some answers on how the different power sources and energy storages can be integrated and controlled using power electronics and feedback control to enhance improved performance, longer life time, increased supply reliability and minimize fuel use. To this end, new control methods and operating strategies are proposed to mediate near optimal intersubsystem power flows. The third part of the thesis concerns grid connected PV-Fuel cell power systems. Control schemes and operating strategies for integrating PV and fuel cell hybrids into the grid to serve both local demand and weak grids are investigated. How hydrogen energy storage and conversion technologies can be controlled to suppress PV fluctuations in future utility grids are also explored. A smoothing algorithm enhanced by a stepwise constant forecast is developed to enable more smooth and subhourly dispatchable power to be fed to the grid. The proposed methods were verified through longtime simulation based on realistic irradiance data over a number of typical days/weeks using suitably defined performance indices. It was learned that using power electronics and sound control methods, PV-hydrogen DGs can be flexibly controlled to solve lifetime and performance issues which are generally considered economic bottle necks. For example, conventionally in PV-hydrogen hybrids, to improve performance and life time, more battery capacity is added to operate fuel cell and electrolyzer under more stable power conditions in the face of highly fluctuating PV generation to prevent low state of charge (SOC) operation of the battery. Contrarily, in this thesis a sound control method is proposed to achieve the same objectives without oversizing the battery. It is shown that the proposed method can give up to 20% higher battery mean state of charge than conventional operation while PV fluctuation suppression rates up to 40% for the fuel cell and 85% for the electrolyzer are found for three typical days. It is also established that by predictively controlling battery SOC instead of conventional SOC setpoint control, substantial improvements can be obtained (up to 20-30% increase in PV energy utilization and ca. 25% reduction in fuel usage for considered days). Concerning use of hydrogen storage and conversion technologies in PV fluctuation suppression, results obtained from the developed smoothing mechanism and performance indices show that a trade-off should be made between smoothing performance and dispatchability. It was concluded that the right size of fuel cell and electrolyzer needs to be selected to optimize the dispatch interval and smoothing performance. Finally, a PV-hydrogen test facility which can act as show case for standalone, grid-connected and UPS applications was designed and built. The test facility was used to characterize key subsystems from which component models developed were experimentally validated. The facility also acted as a reference system for most of the investigations made in this thesis.
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Dzimano, Gwinyai J. "Modeling Of Photovoltaic Systems." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1228307443.
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Alistoun, Warren James. "Investigation of the performance of photovoltaic systems." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1008396.
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The main objective of this study was to investigate the performance of grid integrated PV systems. A data acquisition (DAQ) system was developed to monitor the performance of an existing grid integrated PV system with battery storage. This system is referred to as a grid assisted PV system. A data logger was used together with the inverters built in data logger to monitor environmental and electrical data on a grid tie PV system which was deployed during this study. To investigate the performance of these grid integrated PV systems PV and BOS device characterization was performed. This was achieved by using current voltage curve tracers and the DAQ system developed. Energy yield estimations were calculated referring to the literature review and a meteorological reference for comparison with measured energy yields from the grid tie PV system.
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Njouakoua, Tchonko Leon. "Reconfigurable photovoltaic modules for robust nanosatellite power systems." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2620.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2018.Until recently, the focus of most solar technology development for space was towards more efficient, more radiation-resistant and increasingly powerful arrays. During a space mission, solar cells are not only exposed to irradiation by electrons, but also to a range of other particles, like protons. Thus, solar cells on robust nanosatellites are extremely exposed to an environment, which includes the high-energy electrons and protons of the earth’s radiation belts, which leads towards the degradation process of the individual solar cell. Solar cell radiation shielding design ensures the protection of the solar cells from the particular radiation environment found in space. While the design principles of a solar photovoltaic automatic switching fault tolerant system which can detect and bypass faulty photovoltaic cells will be presented through this research work. The ability of such a system to be reconfigured using implemented switching matrix system makes it efficient under various environments and faulty conditions.
National Research Foundation (NRF)
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Carr, Anna J. "A detailed performance comparison of PV modules of different technologies and the implications for PV system design methods /." Access via Murdoch University Digital Theses Project, 2005. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20050830.94641.
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Thantsha, Nicolas Matome. "Spatially resolved opto-electric measurements of photovoltaic materials and devices." Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1123.
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The objective of this study is to characterize and analyse defects in solar cell devices. Materials used to fabricate solar cells are not defects free and therefore, there is a need to investigate defects in cells. To investigate this, a topographical technique was developed and employed which uses a non-destructive methodology to analyse solar cells. A system was built which uses a technique based on a laser beam induced current (LBIC). LBIC technique involves focusing light on to a surface of a solar cell device in order to create a photo-generated current that can be measured in the external circuit for analyses. The advantage of this technique is that it allows parameter extraction. Parameters that can be extracted include short-circuit current, carrier lifetime and also the external and internal quantum efficiency of a solar cell. In this thesis, LBIC measurements in the form of picture maps are used to indicate the distribution of the localized beam induced current within solar cells. Areas with low minority carrier lifetime in solar cells are made visible by LBIC mapping. Surface reflection intensity measurements of cells can also be mapped using the LBIC system developed in this study. The system is also capable of mapping photo-generated current of a cell below and above room temperature. This thesis also presents an assessment procedure capable of assessing the device and performance parameters with reference to I-V measurements. The dark and illuminated I-V characteristics of solar cells were investigated. The illuminated I-V characteristics of solar cells were obtained using a defocused laser beam. Dark I-V measurements were performed by applying voltage across the cell in the dark and measuring a current through it. The device parameters which describe the behaviour of I-V characteristic were extracted from the I-V data using Particle Swarm Optimization (PSO) method based on a one-and two-diode solar cell models. Solar cells of different technologies were analysed, namely, single-crystalline (c-Si) and multicrystalline (mc-Si) silicon, Edge-defined Film-fed Growth Si (EFG-Si) and Cu(In,Ga)(Se,S)2 (CIGSS) thin film based cells. The LBIC results illustrated the effect of surface reflection features and material defects in the solar cell investigated. IQE at a wavelength of 660 nm were measured on these cells and the results in general emphasised the importance of correcting optical losses, i.e. reflection loss, when characterizing different types of defects. The agreement between the IQE measurements and I-V characteristics of a cell showed that the differences in crystal grains influence the performance of a mc-Si cell. The temperature-dependence of I-V characteristics of a CIGSS solar cell was investigated. The results showed that, for this material, the photo response is reduced at elevated temperatures. In addition to LBIC using a laser beam, solar spectral radiation was employed to obtained device performance parameters. The results emphasised the effect of grain boundaries as a recombination centres for photo-generated hole-pairs. Lastly, mesa diode characterizations of solar cells were investigated. Mesa diodes are achieved by etching down a solar cell so that the plateau regions are formed. Mesa diodes expose the p-n junction, and therefore mesa diode analysis provides a better way of determining and revealing the fundamental current conduction mechanism at the junction. Mesa diodes avoid possible edge effects. This study showed that mesa diodes can be used to characterize spatial non-uniformities in solar cells. The results obtained in this study indicate that LBIC is a useful tool for defect characterization in solar cells. Also LBIC complements other characterization techniques such as I-V characterization.
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Vourazelis, Dimitrios G. "Optimization in solar heating/photovoltaic systems." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA242363.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Titus, Harold A. Second Reader: Michael, Sherif. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Descriptor(s): Heat Transfer, Theory, Theses, Costs, Heating Elements, Fluid Dynamics, Photovoltaic Effect, Solar Heating, Swimming, Optimization, Installation. DTIC Identifier(s): Swimming Pools, Solar Heating, Photovoltaic Supplies, Filter Pumps, Theses. Author(s) subject terms: Optimization, Solar Heating, Photovoltaics. Includes bibliographical references (p. 57). Also available in print.
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Gow, John A. "Modelling, simulation and control of photovoltaic converter systems." Thesis, Loughborough University, 1998. https://dspace.lboro.ac.uk/2134/6871.
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The thesis follows the development of an advanced solar photovoltaic power conversion system from first principles. It is divided into five parts. The first section shows the development of a circuit-based simulation model of a photovoltaic (PV) cell within the 'SABER' simulator environment. Although simulation models for photovoltaic cells are available these are usually application specific, mathematically intensive and not suited to the development of power electronics. The model derived within the thesis is a circuit-based model that makes use of a series of current/voltage data sets taken from an actual cell in order to define the relationships between the cell double-exponential model parameters and the environmental parameters of temperature and irradiance. Resulting expressions define a 'black box' model, and the power electronics designer may simply specify values of temperature and irradiance to the model, and the simulated electrical connections to the cell provide the appropriate I/V characteristic. The second section deals with the development of a simulation model of an advanced PVaware DC-DC converter system. This differs from the conventional in that by using an embedded maximum power tracking system within a conventional linear feedback control arrangement it addresses the problem of loads which may not require the level of power available at the maximum power point, but is also able to drive loads which consistently require a maximum power feed such as a grid-coupled inverter. The third section details a low-power implementation of the above system in hardware. This shows the viability of the new, fast embedded maximum power tracking system and also the advantages of the system in terms of speed and response time over conventional systems. The fourth section builds upon the simulation model developed in the second section by adding an inverter allowing AC loads (including a utility) to be driven. The complete system is simulated and a set of results obtained showing that the system is a usable one. The final section describes the construction and analysis of a complete system in hardware (c. 500W) and identifies the suitability of the system to appropriate applications.
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Ropp, Michael Eugene. "Design issues for grid-connected photovoltaic systems." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13456.
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Gerber, Jacques Dewald. "On the thermal and electrical properties of low concentrator photovoltaic systems." Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1021219.
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Low concentrator photovoltaic systems are capable of increasing the power produced by conventional silicon photovoltaic cells, thus effectively lowering the cost per kWh. However, power losses associated with resistance and temperature have limited the large scale implementation of this technology. In this study, the optical-,electrical- and thermal sub-systems of a low concentrator photovoltaic system are theoretically and experimentally evaluated with the aim of minimizing the power losses associated with series resistance and temperature. A 7-facet reflector system, with an effective concentration ratio of 4.7, is used to focus irradiance along a string of series connected poly-crystalline photovoltaic cells. I-V characteristics of 4-, 6- and 8-cell photovoltaic receivers are measured under 1-sun and 4.83-sun conditions. Under concentration, the 8-cell photovoltaic receiver produced 23 percent more power than the 4-cell photovoltaic receiver, which suggests that the effect of series resistance can be minimized if smaller, lower current photovoltaic cells are used. A thermal model, which may be used to predict operating temperatures of a low concentrator photovoltaic system, is experimentally evaluated within a thermally insulated enclosure. The temperatures predicted by the thermal model are generally within 5 percent of the experimental temperatures. The high operating temperatures associated with the low concentrator photovoltaic system are significantly reduced by the addition of aluminium heat sink. In addition, the results of a thermal stress test indicated that these high operating temperatures do not degrade the photovoltaic cells used in this study. The results of this study suggest that the power output of low concentrator photovoltaic systems can be maximized by decreasing the size of the photovoltaic cells and including an appropriate heat sink to aid convective cooling.
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Lin, Chen. "Experimental investigations on performance enhancement of a photovoltaic cooling system." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3691167.
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Häggblom, Johan, and Jonathan Jerner. "Photovoltaic Power Production and Energy Storage Systems in Low-Voltage Power Grids." Thesis, Linköpings universitet, Fordonssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156875.
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In recent years, photovoltaic (PV) power production have seen an increase and the PV power systems are often located in the distribution grids close to the consumers. Since the distributions grids rarely are designed for power production, investigation of its effects is needed. It is seen in this thesis that PV power production will cause voltages to rise, potentially to levels exceeding the limits that grid owners have to abide by. A model of a distribution grid is developed in MathWorks MATLAB. The model contains a transformer, cables, households, energy storage systems (ESS:s) and photovoltaic power systems. The system is simulated by implementing a numerical Forward Backward Sweep Method, solving for powers, currents and voltages in the grid. PV power systems are added in different configurations along with different configurations of ESS:s. The results are analysed, primarily concerning voltages and voltage limits. It is concluded that addition of PV power production in the distribution grid affects voltages, more or less depending on where in the grid the systems are placed and what peak power they have. It is also concluded that having energy storage systems in the grid, changing the power factor of the inverter for the PV systems or lowering the transformer secondary-side voltage can bring the voltages down.På senare tid har det skett en ökning i antalet solcellsanläggningar som installeras i elnätet och dessa är ofta placerade i distributionsnäten nära hushållen. Eftersom distributionsnäten sällan är dimensionerade för produktion så behöver man utreda effekten av det. I det här arbetet visas det att solcellsproduktion kommer att öka spänningen i elnätet, potentiellt så mycket att de gränser elnätsägarna måste hålla nätet inom överstigs. En modell över lågspänningsnätet skapas i MathWorks MATLAB. Modellen innehåller transformator, kablar, hushåll, energilager och solcellsanläggningar. Systemet simuleras med hjälp av en numerisk Forward Backward Sweep-lösare som beräknar effekter, strömmar och spänningar i elnätet. Solcellanläggningarna placeras ut i elnätet i olika konfigurationer tillsammans med olika konfigurationer av energilager. Resultaten från simuleringarna analyseras främst med avseende på spänningen i elnätet utifrån dess gränser. De slutsatser som dras i arbetet är att solcellsproduktion kommer att påverka spänningen, mycket beroende på var i elnätet anläggningarna placeras och storleken hos dem. Det visas också att energilager, justering av effektfaktor hos solcellsanläggningarna eller en spänningssänkning på transformatorns lågspänningssida kan få ner spänningen i elnätet.
LiTH-ISY-EX--19/5194--SE
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Jantharamin, Niphat. "Optimal control and management of photovoltaic power generation systems." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556249.
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Wang, Menghong. "Degradation of Photovoltaic Packaging Materials and Power Output of Photovoltaic Systems: Scaling up Materials Science with Data Science." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1595416965256375.
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Venkatraman, Chandrasekar. "Hill climbing digital control algorithm for maximum power point tracking of photovoltaic arrays." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1320938081&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Macabebe, Erees Queen Barrido. "Investigation of device and performance parameters of photovoltaic devices." Thesis, Nelson Mandela Metropolitan University, 2009. http://hdl.handle.net/10948/1003.
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In order to investigate the influence of parasitic resistances, saturation current and diode ideality factor on the performance of photovoltaic devices, parameter extraction routines employing the standard iteration (SI) method and the particle swarm optimization (PSO) method were developed to extract the series resistance, shunt resistance, saturation current and ideality factor from the I-V characteristics of solar cells and PV modules. The well-known one- and two-diode models were used to describe the behavior of the I-V curve and the parameters of the models were determined by approximation and iteration techniques. The SI and the PSO extraction programmes were used to assess the suitability of the one- and the two-diode solar cell models in describing the I-V characteristics of mono- and multicrystalline silicon solar cells, CISS- and CIGSS-based solar cells. This exercise revealed that the two-diode model provides more information regarding the different processes involved in solar cell operation. Between the two methods developed, the PSO method is faster, yielded fitted curves with lower standard deviation of residuals and, therefore, was the preferred extraction method. The PSO method was then used to extract the device parameters of CISS-based solar cells with the CISS layer selenized under different selenization process conditions and CIGSS-based solar cells with varying i-ZnO layer thickness. For the CISS-based solar cells, the detrimental effect of parasitic resistances on device performance increased when the temperature and duration of the selenization process was increased. For the CIGSS-based devices, photogeneration improved with increasing i-ZnO layer thickness. At high forward bias, bulk recombination and/or tunneling-assisted recombination were the dominant processes affecting the I-V characteristics of the devices. v Lastly, device and performance parameters of mono-, multicrystalline silicon and CIS modules derived from I-V characteristics obtained under dark and illuminated conditions were analyzed considering the effects of temperature on the performance of the devices. Results showed that the effects of parasitic resistances are greater under illumination and, under outdoor conditions, the values further declined due to increasing temperature. The saturation current and ideality factor also increased under outdoor conditions which suggest increased recombination and, coupled with the adverse effects of parasitic resistances, these factors result in lower FF and lower maximum power point. Analysis performed on crystalline silicon and thin film devices utilized in this study revealed that parameter extraction from I-V characteristics of photovoltaic devices and, in particular, the implementation of PSO in solar cell device parameter extraction developed in this work is a useful characterization technique.
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Swanepoel, Paul. "A forecasting model for photovoltaic module energy production." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1420.
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Energy is of concern for governments and economies all over the world. As conventional methods of energy production are facing the prospect of depleting fossil fuel reserves, economies are facing energy risks. With this tension, various threats arise in terms of energy supply security. A shift from intensive fossil fuel consumption to alternative energy consumption combined with the calculated use of fossil fuels needs to be implemented. Using the energy radiated from the sun and converted to electricity through photovoltaic energy conversion is one of the alternative and renewable sources to address the limited fossil fuel dilemma. South Africa receives an abundance of sunlight irradiance, but limited knowledge of the implementation and possible energy yield of photovoltaic energy production in South Africa is available. Photovoltaic energy yield knowledge is vital in applications for farms, rural areas and remote transmitting devices where the construction of electricity grids are not cost effective. In this study various meteorological and energy parameters about photovoltaics were captured in Port Elizabeth (South Africa) and analyzed, with data being recorded every few seconds. A model for mean daily photovoltaic power output was developed and the relationships between the independent variables analyzed. A model was developed that can forecast mean daily photovoltaic power output using only temperature derived variables and time. The mean daily photovoltaic power model can then easily be used to forecast daily photovoltaic energy output using the number of sunlight seconds in a given day.
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Gxasheka, Andile Richman. "On the optical characterization of photovoltaic devices." Thesis, Nelson Mandela Metropolitan University, 2008. http://hdl.handle.net/10948/692.
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Semiconductor materials used for making photovoltaic (PV) cells have defects and impurities due to constraints of keeping production costs low. Electrically active defects that are distributed over the bulk material lead to reduced overall performance of a photovoltaic (PV) cell. In this study an adaptable Light Beam Induced Current (LBIC) system was designed in order to characterize the local performance of PV cells. The system uses a laser source and objective lens mounted vertically above the sample on the X-Y stage. Two current pre-amplifiers are used for converting the photo-generated current from the PV cell and the signal from the reflection detector cell into a voltage that can be measured by the data acquisition board. Two configurations for measuring the photo-current maps of either bare cells or encapsulated PV mini-modules can be used. To add flexibility it was envisaged that the system would be built in such a way that it allows easy integration of carrier lifetime mapping capabilities while keeping costs to a minimum. The carrier lifetime measurement technique integrated into the LBIC system is based on the optical Open-Circuit Voltage-Decay (OCVD) method. In a single-crystalline silicon PV cell that was tested, photo-current and opencircuit voltage LBIC scans revealed shunting behaviour due to scratch marks on the front surface. The marks are believed to have been caused by poor handling during manufacturing process. Reduced photo-current due to edge shunting was observed towards the edges of the PV cell. In another sample of single crystalline silicon cell an edge shunt resulted in a 30 percent drop in photo-current measured. LBIC measurements performed on multi-crystalline cells revealed nonuniformities such as enhanced photo-current on one side of grain boundaries. These asymmetric enhancements of local photo-current are attributed to the incline of the grain boundary into the bulk of the material. LBIC results obtained from mini modules showed a high degree of mismatching from cell to cell. It is well known that mismatching can degrade the performance of a PV module with series connected cells. The LBIC measurements presented also illustrated the negative effects of delamination on the photo-current of PV modules. The LBIC measurements performed on mini PV modules highlight some of the benefits of using an LBIC technique as a tool for investigating PV cell’s local photo-current response. The effective lifetime maps obtained highlight the importance of optical OCVD method as a tool that can be used in conjunction with conventional LBIC technique. Effective minority carrier lifetimes around 40 ms were measured on a single crystalline silicon cell of 2.5 x 2.5 cm2. Local features such as cracks and lifetime degrading defects were revealed by LBIC maps and were also confirmed on effective lifetime maps. The results presented demonstrate the importance of using effective carrier lifetime maps to complement photocurrent maps of PV cells and identification of areas where defects are located.
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Mnider, Abdalbaset Mohamed Husian. "Power quality improvements of single-phase grid-connected photovoltaic systems." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3967.
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The number of distributed power generation systems (DPGSs), mostly based on photovoltaic (PV) energy sources is increasing exponentially. These systems must conform to grid codes to ensure appropriate power quality and to contribute to grid stability. A robust and reliable synchronization to the grid is an important consideration in such systems. This is due to the fact that, fast and accurate detection of the grid voltage parameters is essential in order to implement stable control strategies under a broad range of grid conditions. The second-order generalized integrator (SOGI) based phase-locked loop (PLL) is widely used for grid synchronization of single-phase power converters. This is because it offers a simple, robust and flexible solution for grid synchronization. However, the SOGI-PLL is affected by the presence of a dc offset in the measured grid voltage. This dc voltage offset is typically introduced by the measurements and data conversion process, and causes fundamental-frequency ripple in the estimated parameters of the grid voltage (i.e. voltage amplitude, phase angle and frequency). In addition to this ripple, the unit amplitude sine and cosine signals of the estimated phase angle (i.e. unit vectors), that are used to generate reference signals in the closed-loop control of grid-connected PV converters will contain dc offset. This is highly undesirable since it can cause dc current injection to the grid, and as a consequence, the quality of the power provided by the DPGSs can be degraded. To overcome this drawback, a modified SOGI-PLL with dc offset rejection capability is proposed. The steady-state, transient and harmonic attenuation performance of the proposed PLL scheme are validated through simulation and experimental tests. The overall performance demonstrates the capability of the proposed PLL to fully reject such dc current injection as well as to provide a superior harmonic attenuation when compared with the SOGIPLL and two other existing offset rejection approaches. It is shown that, the proposed PLL scheme can enhance the overall total harmonic distortion (THD%) of the injected power by 15% when compared to the conventional SOGI-PLL. In addition to the synchronization, grid-connected PV systems require a current control scheme to regulate the output current. Due to the simple implementation, proportional-integral (PI) controllers in the stationary reference frame are commonly used for current controlled inverters. However, these PI-controllers exhibit a major drawback of failure to track a sinusoidal reference Abstract ii without steady-state error, which may result in low-order harmonics. This drawback can be overcome if the PI-controllers are implemented in direct-quadrature (dq) rotating reference frame. In single-phase systems, the common approach is to create a synthesized phase signal orthogonal to the fundamental of the real single-phase system so as to obtain dc quantities by means of a stationary-to-rotating reference frame. The orthogonal synthesized signal in conventional approaches is obtained by phase shifting the real signal by a quarter of the fundamental period. The introduction of such delay in the system deteriorates the dynamic response, which becomes slower and oscillatory. This thesis proposes an alternative way of implementing such PI-controllers in the dq reference frame without the need of creating such orthogonal signals. The proposed approach, effectively improves the poor dynamic of the conventional approaches while not adding excessive complexity to the controller structure. The results show that, in addition to its ability to regulate the current and achieve zero steady-state error, the proposed approach shows superior dynamic response when compared with that of conventional delay-based approach.
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Coventry, Joseph Sydney. "A solar concentrating photovoltaic/thermal collector /." View thesis entry in Australian Digital Theses Program, 2004. http://thesis.anu.edu.au/public/adt-ANU20041019.152046/index.html.
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Chu, Yiu-cheong. "Application of energy saving systems in Hong Kong buildings /." Hong Kong : University of Hong Kong, 2002. http://sunzi.lib.hku.hk/hkuto/record.jsp?B25549406.
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Prichard, Martin Edward. "SINGLE PHASE MULTILEVEL INVERTER FOR GRID-TIED PHOTOVOLTAIC SYSTEMS." UKnowledge, 2015. http://uknowledge.uky.edu/ece_etds/81.
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Multilevel inverters offer many well-known advantages for use in high-voltage and high-power applications, but they are also well suited for low-power applications. A single phase inverter is developed in this paper to deliver power from a residential-scale system of Photovoltaic panels to the utility grid. The single-stage inverter implements a novel control technique for the reversing voltage topology to produce a stepped output waveform. This approach increases the granularity of control over the PV systems, modularizing key components of the inverter and allowing the inverter to extract the maximum power from the systems. The adaptive controller minimizes harmonic distortion in its output and controls the level of reactive power injected to the grid. A computer model of the controller is designed and tested in the MATLAB program Simulink to assess the performance of the controller. To validate the results, the performance of the proposed inverter is compared to that of a comparable voltage-sourced inverter.
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Pappu, Venkata Ajay Kumar. "Implementing frequency regulation capability in a solar photovoltaic power plant." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2010. http://scholarsmine.mst.edu/thesis/pdf/Pappu_09007dcc807d51ca.pdf.
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Thesis (M.S.)--Missouri University of Science and Technology, 2010.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed July 19, 2010) Includes bibliographical references (p. 88-90).
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Khallat, Mohamed Ali. "A methodology for evaluating photovoltaic-fuel hybird energy systems." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/53626.
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A major issue encountered in the large scale use of Photovoltaic (PV) energy sources for the production of electricity is the variability of the resource itself. Extensive fluctuations of the PV generation may cause dynamic operational problems for an electric utility. In order to remedy this situation it is proposed that fuel cell power plants be operated in parallel with PV arrays. This hybrid operation will help to smooth out the fluctuating PV output. Because of its high ramping capability the fuel cell will be able to absorb such fluctuations.
An overall methodology is presented to evaluate the PV system in a large utility. This methodology has two parts-planning and operation. The aim of the planning study is to determine the capacity credit of a PV system based on the loss of load probability (LOLP). Long term SOLMET data is used to determine the nature of available insolation at a particular site. The expected value of hourly insolation is used in the planning study. The aim of the operation study is to validate the results of planning study in the shorter operational time frame, and determine the fuel cell requirements and associated operating cost savings for each penetration level of PV.
A technique to find the maximum penetration level of PV, without causing any economic penalty, is presented. It is found that the penetration level can be increased up to 15.62% of peak load by adding fuel cells to the system under consideration. The annual peak load for this system is taken as 6400 MW. It must be mentioned here that, similar evaluations for other systems may yield somewhat different results. This technique is general enough such that it can be used for other intermittent sources of generation as well.Ph. D.
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Fung, Yu Yan. "Energy performance of semi-transparent PV modules for applications in buildings." online access from Digital Dissertation Consortium, 2006. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?3241058.
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cooper, sean. "Control of a Satellite Based Photovoltaic Array for Optimum Power Draw." Digital WPI, 2008. https://digitalcommons.wpi.edu/etd-theses/414.
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This thesis analyzes the general performance and design requirements of photovoltaic(PV) systems, and specifically how they relate to the design of a system intended to supply power to a rotating satellite. The PV array geometry was discussed, different DC-DC converter topologies were analyzed, and optimum array geometry and converter topologies were determined. The potential reference quantities for use in control of the system are examined. Due to its comparably greater linearity with respect to changes in apparent load and its relative insensitivity to insolation changes, voltage was determined to be the best reference quantity for use in stable tracking of the maximum power operating point of photovoltaic modules. The preceding work is used to design and model a photovoltaic system for a rotating satellite ensuring the supply of the maximum available power as well as stable operation. Simulations of the system are performed at rotational velocities up to 300 rev/min and its behavior is analyzed to demonstrate the validity of the preceding work. It was concluded that: ● parallel connected photovoltaic panels provide greater efficiency than series connected panels. ● Buck, Boost, and Cuk Converter architectures are best suited to PV applications ● PV Voltage is the best reference quantity for use in stable control of PV systems.
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Alam, Mohammad Saad. "Real-time maximum power tracking and robust load matching of a stand-alone photovoltaic system a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online, 2009. http://proquest.umi.com/pqdweb?index=0&did=1756844361&SrchMode=1&sid=2&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1280170042&clientId=28564.
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Crozier, Jacqueline Louise. "Characterisation of performance limiting defects in photovoltaic devices using electroluminescence and related techniques." Thesis, Nelson Mandela Metropolitan University, 2015. http://hdl.handle.net/10948/11004.
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Solar cells allow the energy from the sun to be converted into electrical energy; this makes solar energy an environmentally friendly, sustainable alternative to fossil fuel energy sources. Solar cells are connected together in a photovoltaic (PV) module to provide the higher current, voltage and power outputs necessary for electrical applications. However, the performance of PV modules can limited by the degradation and defects. PV modules can be characterised using various opto-electronic techniques, each providing information about the performance of the module. The current-voltage (I-V) characteristic curve of a module being the most commonly used characterisation technique. The I-V curve is typically measured in outdoor, fully illuminated, conditions. This allows performance parameters such as short circuit current (ISC), open circuit voltage (VOC) and maximum power (PMAX) to be determined. However, it can be difficult to determine the root cause of the performance drop from the I-V curve alone. Electroluminescence (EL) is a module characterisation technique that allows defects and failures in PV modules to be successfully identified. This study investigates the characterisation of solar cells and photovoltaic modules using EL. EL occurs when a solar cell or module is forward biased and the injected electron-hole pairs recombine radiatively. The intensity of the emitted EL is related the applied voltage and the material properties. EL imaging is a useful characterisation technique in identifying module defects and failures. Defects such as micro-cracks, broken contact fingers and fractures are detected in EL images as well as material features such as grain boundaries. The common defects in crystalline silicon are catalogued and the possible causes are discussed. An experimental setup was developed in order to systematically take a high resolution EL image of every cell in the module and record the applied voltage and current. This produces a very detailed, clear, image of each cell with a pixel size in the micrometre range. This process is time consuming to acquire an EL image of an entire module so alternatively a different setup can be used and an EL image of a whole module can be captured in a single frame with an increased pixel size in the millimetre range. For EL imaging a silicon charge-coupled device (CCD) camera was used because it has very good spatial resolution however this sensor is only sensitive to wavelength in the range of 300-1200 nm. There is an overlap in wavelengths from about 900 to 1100 nm allowing the EL emitted from silicon solar cells to be detected. In conjunction with the high-resolution EL system an image processing program was developed to crop, adjust and align the images so only the relevant cell was included. This program also automatically detects certain defects that have a regular shape. Micro-cracks, broken fingers and striation rings are automatically identified. The program has an adjustable sensitivity to identify small or large defects. Defective cells are distinguished from undamaged cells by comparing the binary images to the ideal, undamaged cell. The current-voltage curves and the performance parameters of modules were compared with the EL images in order to discuss and identify power limiting defects. Features that remove significant portions of the cell from electrical contact such as micro-cracks are shown to have a larger effect of the performance of the module. Other features such as broken contact fingers, contact forming failures and striation rings do not significantly lower the performance of the module. Thus an understanding of how different features affect the module performance is important in order to correctly interpret the EL results. The intensity of the luminescence emitted is related to the applied voltage and the quantum efficiency of the cell material. The spectrum of the emitted luminescence was modelled and related to the recombination properties of the cell such as surface recombination velocity and minority carrier diffusion length/lifetime. In this study the emitted spectrum was modelled and the effects of recombination properties of the cell on the emitted spectrum were examined. The spectrum of the detected EL was modelled, dependent on the sensitivity of the camera, the transmission of the filters and the emitted photon flux. The integration of short-pass filters into the experimental setup in order to isolate short-wavelength luminescence was discussed. There is a proportional relationship between the intensity of the emitted EL and the local junction voltage. Resistive losses like series and shunt resistances lower the applied voltage and thus affect the EL image. The voltage dependence was assessed by comparing EL images taken at different applied biases. Analysis of the variation in EL intensity with voltage was successful in determining the origin of certain features in an EL image. Certain defects, those that are related to series resistance or shunting are highly voltage dependent. When a feature has little or no dependence on voltage then the defect could be in the laminate layers and not in the cell material. The results of this study allow for in-depth analysis of the defects found in PV modules using the high resolution EL imaging system and the image processing routine. The development of an image processing routine allows the interpretation of the EL image to be done automatically, resulting in a faster and more efficient process. By understanding the defects visible in the EL image, the test is more meaningful and allows the results to be used to predict module performance and potential failures.
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Pregelj, Aleksandar. "Impact of Distributed Generation on Power Network Operation." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/5127.
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Tools and algorithms are proposed that are useful for planning, designing, and operating a distribution network with a significant penetration of distributed generation (DG). In Task 1, a PV system simulation program is developed, which incorporates the most rigorous models for the calculation of insolation, module temperature, and DC and AC power output of a PV system. The effect of random inverter failures is incorporated in the model of a PV system, and a novel performance-derating coefficient is introduced. Furthermore, a novel inverter control algorithm is presented for systems with multiple inverters. The algorithm is designed to increase overall DC/AC conversion efficiency by selectively shutting down some of the inverters during periods of low insolation, thus forcing the remaining inverters to operate at higher efficiency. In Task 2, a procedure is developed to incorporate the uncertainties imposed by stochastic, renewable DG into the conventional tools for analysis of distribution systems. A clustering algorithm is proposed to reduce large input data sets that result from the interaction of stochastic processes that drive DG output with field measurements of feeder load profiles. In addition, a procedure is proposed to determine the boundary points of the original data set, which yield feeder extreme operating conditions. Finally, a Monte Carlo analysis using a reduced data set is presented, to determine the effects of deploying a large number of renewable DG systems on a distribution feeder. In Task 3, the reliability model of an asymmetric, three--phase, non-radial distribution feeder equipped with capacity-constrained DGs is developed and used to quantify the potential reliability improvements due to the intentional islanded operation of parts of the feeder. A procedure for finding optimal positions for DG and protection devices is presented using a custom-tailored adaptive genetic algorithm.
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Sokolov, Michael. "Small-signal modelling of maximum power point tracking for photovoltaic systems." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/39348.
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In grid connected photovoltaic (PV) generation systems, inverters are used to convert the generated DC voltage to an AC voltage. An additional dc-dc converter is usually connected between the PV source and the inverter for Maximum Power Point Tracking (MPPT). An iterative MPPT algorithm searches for the optimum operating point of PV cells to maximise the output power under various atmospheric conditions. It is desirable to be able to represent the dynamics of the changing PV power yield within stability studies of the AC network. Unfortunately MPPT algorithms tend to be nonlinear and/or time-varying and cannot be easily combined with linear models of other system elements. In this work a new MPPT technique is developed in order to enable linear analysis of the PV system over reasonable time scales. The new MPPT method is based on interpolation and an emulated-load control technique. Numerical analysis and simulations are employed to develop and refine the MPPT. The small-signal modelling of the MPPT technique exploits the fact that the emulated-load control technique can be linearised and that short periods of interpolation can be neglected. A small-signal PV system model for variable irradiation conditions was developed. The PV system includes a PV module, a dc-dc boost converter, the proposed controller and a variety of possible loads. The new model was verified by component-level time-domain simulations. Be cause measured signals in PV systems contain noise, it is important to assess the impact of that noise on the MPPT and design an algorithm that operates effectively in pr esence of noise. For performance assessment of the new MPPT techniques, the efficiencies of various MPPT techniques in presence of noise were compared. This comparison showed superiority of the interpolation MPPT and led to conclusions about effective use of existing MPPT methods. The new MPPT method was also experimentally tested.
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Cooper, Sean. "Control of a satellite based photovoltaic array for optimum power draw." Worcester, Mass. : Worcester Polytechnic Institute, 2008. http://www.wpi.edu/Pubs/ETD/Available/etd-042808-104913/.
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Guerin, Vincent. "Optimization of the operation and monitoring of large-scale photovoltaic power plant." Thesis, KTH, Energiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-263901.
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The monitoring and supervision of large scale solar photovoltaic plants becomes more and more important nowadays, with the increase of the installed power. The detection system and the reactivity must be improved in order to allow the plants to run at their best capacity. One way to improve that detection is the setup of alerts triggering for certain types of defaults concerning the performance of the inverters or the plant itself. That setup can be optimized by analytical analysis on the historic data of the plant, and adjusted for each plant, depending on its behavior. Another way is to calculate robust indicators such as the performance ratio, which corresponds to the efficiency of the plant, regardless the type of installed panels. This indicator depends on the electricity production and the received irradiance. In order to have an accurate measure of that indicator, a work on the reconstitution of the missing data must be done for the irradiance measure. That reconstitution enables to have access to a robust measure of the performance ratio and thus to improve the monitoring of the performances of the plant.Övervakningen av fotovoltaisk anläggning blir mer och mer viktigt idag, med ökningen av den installerade kraften. Detekteringssystemet och reaktiviteten måste förbättras för att växterna ska kunna köras med bästa kapacitet. Ett sätt att förbättra detekteringen är att upprätta larm som utlöser för vissa typer av standardvärden beträffande inverterarnas prestanda eller själva anläggningen. Denna inställning kan optimeras genom analytisk analys av anläggningens historiska data och justeras för varje anläggning, beroende på dess beteende. Ett annat sätt är att beräkna robusta indikatorer som prestandaförhållandet, vilket motsvarar anläggningens effektivitet, oavsett typ av installerade paneler. Denna indikator beror på elproduktionen och den mottagna bestrålningen. För att ha ett exakt mått på den indikatorn måste ett arbete med rekonstitution av de saknade uppgifterna göras för bestrålningsåtgärden. Denna rekonstitution möjliggör åtkomst till ett robust mått på prestandaförhållandet och därmed förbättrar övervakningen av anläggningens prestanda.
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Bollinger, Joshua David. "Applications of solar energy to power stand-alone area and street lighting." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.umr.edu/thesis/pdf/Joshua_Bollinger_Thesis_09007dcc8031b71d.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed April 17, 2007) Includes bibliographical references (p. 88-91).
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Hayman, Rebecca. "A DSP Algorithm for Multi-Channel Maximum Power Point Tracking in Photovoltaic Systems." Honors in the Major Thesis, University of Central Florida, 2004. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/719.
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This item is only available in print in the UCF Libraries. If this is your Honors Thesis, you can help us make it available online for use by researchers around the world by following the instructions on the distribution consent form at http://library.ucfBachelors
Engineering and Computer Science
Electrical Engineering
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Foreman, Mark McKinney. "Control and operation of SMES and SMES/PV systems." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-10062009-020156/.
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LaBella, Thomas Matthew. "A High-Efficiency Hybrid Resonant Microconverter for Photovoltaic Generation Systems." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50526.
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The demand for increased renewable energy production has led to increased
photovoltaic (PV) installations worldwide. As this demand continues to grow, it is
important that the costs of PV installations decrease while the power output capability
increases. One of the components in PV installations that has lots of room for improvement
is the power conditioning system. The power conditioning system is responsible for
converting the power output of PV modules into power useable by the utility grid while
insuring the PV array is outputting the maximum available power. Modular power
conditioning systems, where each PV module has its own power converter, have been
proven to yield higher output power due to their superior maximum power point tracking
capabilities. However, this comes with the disadvantages of higher costs and lower power
conversion efficiencies due to the increased number of power electronics converters. The
primary objective of this dissertation is to develop a high-efficiency, low cost
microconverter in an effort to increase the output power capability and decrease the cost of
modular power conditioning systems.
First, existing isolated dc-dc converter topologies are explored and a new topology
is proposed based on the highly-efficient series resonant converter operating near the series
resonant frequency. Two different hybrid modes of operation are introduced in order to
add wide input-voltage regulation capability to the series resonant converter while
achieving high efficiency through low circulating currents, zero-current switching (ZCS)
of the output diodes, zero-voltage switching (ZVS) and/or ZCS of the primary side active
switches, and direct power transfer from the source to the load for the majority of the
switching cycle. Each operating mode is analyzed in detail using state-plane trajectory
plots. A systematic design approach that is unique to the newly proposed converter is
presented along with a detailed loss analysis and loss model. A 300-W microconverter
prototype is designed to experimentally validate the analysis and loss model. The converter
featured a 97.7% weighted California Energy Commission (CEC) efficiency with a
nominal input voltage of 30 V. This is higher than any other reported CEC efficiency for
PV microconverters in literature to date.
Each operating mode of the proposed converter can be controlled using simple
fixed-frequency pulse-width modulation (PWM) based techniques, which makes
implementation of control straightforward. Simplified models of each operating mode are
derived as well as control-to-input voltage transfer functions. A smooth transition method
is then introduced using a two-carrier PWM modulator, which allows the converter to
transition between operating modes quickly and smoothly. The performance of the voltage
controllers and transition method were verified experimentally.
To ensure the proposed converter is compatible with different types of modular
power conditioning system architectures, system-level interaction issues associated with
different modular applications are explored. The first issue is soft start, which is necessary
when the converter is beginning operation with a large capacitive load. A novel soft start
method is introduced that allows the converter to start up safely and quickly, even with a
short-circuited output. Maximum power point tracking and double line frequency ripple
rejection are also explored, both of which are very important to ensuring the PV module is
outputting the maximum amount of available power.
Lastly, this work deals with efficiency optimization of the proposed converter. It
is possible to use magnetic integration so that the resonant inductor can be incorporated
into the isolation transformer by way of the transformer leakage inductance in order to
reduce parts count and associated costs. This chapter, however, analyzes the disadvantages
to this technique, which are increased proximity effect losses resulting in higher conduction
losses. A new prototype is designed and tested that utilizes an external resonant inductor
and the CEC efficiency was increased from 97.7% to 98.0% with a marginal 1.8% total
cost increase. Additionally, a variable frequency efficiency optimization algorithm is
proposed which increases the system efficiency under the high-line and low-line input
voltage conditions. This algorithm is used for efficiency optimization only and not control,
so the previously presented simple fixed-frequency modeling and control techniques can
still be utilized.Ph. D.
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Levy, Michael Yehuda. "Design, experiment, and analysis of a photovoltaic absorbing medium with intermediate levels." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24703.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Honsberg, Christiana; Committee Co-Chair: Citrin, David; Committee Member: Doolittle, Alan; Committee Member: First, Phillip; Committee Member: Ralph, Stephen; Committee Member: Rohatgi, Ajeet
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Williams, Nathaniel John. "On the design and monitoring of photovoltaic systems for rural homes." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/1308.
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It is estimated that 1.6 billion people today live without access to electricity. Most of these people live in remote rural areas in developing countries. One economic solution to this problem is the deployment of small domestic photovoltaic (PV) systems called solar home systems (SHS). In order to improve the performance and reduce the life cycle cost of these systems, accurate monitoring data of real SHSs is required. To this end, two SHSs typical of those found in the field were designed and installed, one in a rural area of the Eastern Cape of South Africa and the other in the laboratory. Monitoring systems were designed to record energy ows in the system and important environmental parameters. A novel technique was developed to correct for measurement errors occurring during the utilization of pulse width modulation charge control techniques. These errors were found to be as large as 47.6 percent. Simulations show that correction techniques produce measurement errors that are up to 20 times smaller than uncorrected values, depending upon the operating conditions. As a tool to aid in the analysis of monitoring data, a PV performance model was developed. The model, used to predict the maximum power point (MPP) power of a PV array, was able to predict MPP energy production to within 0.2 percent over the course of three days. Monitoring data from the laboratory system shows that the largest sources of energy loss are charge control, module under performance relative to manufacturer specifications and operation of the PV array away from MPP. These accounted for losses of approximately 18-27 percent, 15 percent and 8-11 percent of rated PV energy under standard test conditions, respectively. Energy consumed by loads on the systems was less than 50 percent of rated PV energy for both the remote and laboratory systems. Performance ratios (PR) for the laboratory system ranged from 0.38 to 0.49 for the three monitoring periods. The remote system produced a PR of 0.46. In both systems the PV arrays appear to have been oversized. This was due to overestimation of the energy requirements of the loads on the systems. In the laboratory system, the loads consisting of three compact fluorescent lamps and one incandescent lamp, were used to simulate a typical SHS load pro le and collectively consumed only 85 percent of their rated power. The 8 predicted load profile for the remote system proved to be signi cantly overestimated. The results of the monitoring project demonstrate the importance of acquiring an accurate estimation of the energy demand from loads on the system. Overestimations result in over-sized arrays and energy lost to charge control while under-sized systems risk damaging system batteries and load shedding. Significant under-performance of the PV module used in the laboratory system, underlines the importance of measuring module IV curves and verifying manufacturer specifications before system deployment. It was also found that signi cant PV array performance gains could be obtained by the use of maximum power point tracking charge controllers. Increased PV array performance leads to smaller arrays and reduced system cost.
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Warren, Jeremy. "Optimizing performance in photovoltaic devices based on conjugated poly(phenylene vinylenes)." Akron, OH : University of Akron, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=akron1144257019.
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Dissertation (Ph. D.)--University of Akron, Dept. of Polymer Science, 2006."May, 2006." Title from electronic dissertation title page (viewed 10/11/2006) Advisor, Frank W. Harris; Committee members, Stephen Z. D. Cheng, David A. Modarelli, Judit Puskas, William J. Brittain; Department Chair, Mark D. Foster; Dean of the College, Frank N. Kelley; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.
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Hasan, KN. "Control of power electronic interfaces for photovoltaic power systems." Thesis, 2009. https://eprints.utas.edu.au/20717/1/whole_HasanKaziNazmul2009_thesis.pdf.
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This thesis deals with the control of power electronic interfaces for photovoltaic applications. The main objective is to develop and employ effective control algorithms and topologies that are optimally suited for photovoltaic power conversion systems. The studies, comprising of analysis, modeling, control and experimental evaluation, clearly enhance overall system performance. The major items of investigation in this thesis are power electronic converter design and modeling, current mode control, maximum power point tracking techniques, and control for energy storage systems.
The nonlinear and time varying characteristics of both the photovoltaic module and switch-mode power converters cause problems in photovoltaic systems control. The weather dependency of photovoltaic system makes these problems even more severe. As the photovoltaic source usually acts as a current source, this thesis proposes current mode control methods as a suitable control solution in photovoltaic power systems. The thesis proposes an improved algorithm, based on current mode control, to ensure an accurate tracking of the maximum power point of the photovoltaic module. In addition, four current mode control methods are investigated for the dc-dc converter controller to obtain a stable dc bus voltage. The results obtained are compared with the voltage mode control. Finally, a new control algorithm is proposed for charging and discharging of the photovoltaic battery storage system, which allows versatile power transfer among the photovoltaic source, battery and load.
Extensive simulation studies were performed based on MATLAB/Simulink/ Simpower to verify the control methods of the maximum power point tracking, dc-dc converter control and energy storage interface for a 3 KW photovoltaic power system. The current mode control methods have shown significant improvement in different aspects of the power quality, especially in case of input changes, load variations, transient responses and harmonics. A dSPACE DS1104 DSP (digital signal processor) hardware and software system was used in a prototype experimental evaluation to validate the improved performances of the current mode control of dc-dc converter for photovoltaic systems.
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Phang, Lau Shown, and 劉舜鵬. "Development of Micro-Photovoltaic Power Conversion Systems." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/md6k7j.
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碩士國立臺灣科技大學
電機工程系
99
This thesis develops a micro-photovoltaic(PV) solar power system. The system contains a DC-DC power converter and a DC-AC power converter. DC-DC power converter uses a new high step-up ratio isolated DC-DC power converters to boost the output high voltage from solar cells. DC-AC power converter is a single-phase full-bridge inverter which can be either operated in stand-alone fashion with voltage control or connected with power grid using current control. In this thesis, a new feed-forward compensation with maximum power point tracking of PV system, together with current control mode are proposed to generate maximum solar power to the grid. Digital signal processor TMS320F28035 is used to control the system with voltages and currents. The overall system can be operated either in voltage or current closed-loop control. This system can not only connect to grid, but also has a power failure detection and restoration capabilities to achieve plug and play function. A 200W micro-PV solar power system is built with solar cell voltage 20V ~ 30V, AC side voltage 110V , 60Hz. The overall efficiency at full load is 0.94. The experimental results verify the feasibility of the proposed system.
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Nayak, Biswabandhu. "Assesment of Power Quality of Photovoltaic Generations." Thesis, 2015. http://ethesis.nitrkl.ac.in/7466/1/129.pdf.
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In the recent times distributed generations or renewable energies are very much needed for daily usage as the natural resources are on the verge of extinction. These renewable energy sources are a very good solution for the global energy problem. The usage of renewable energy, according to the statistics is around 17% all over the world, from which only 0.06% constitute of solar PV power. These statistics show that we are lagging behind from extracting the solar power. There are various factors that can be hold accountable for this viz. very costly equipment, lack of knowledge and even we do not have enough technology to harness the solar power. Solar power, as most renewable energy sources, is not a steady power source. We only can utilize or store it during daytime. We try to find the maximum power point (MPP) of the PV array and then it is supplied to the grid. There are two different methods to track the MPP – Perturb and Observe (P&O) method and Maximum Power Point Tracking algorithm method (MPPT). In this project MPPT algorithm is used to track the MPP. The MPPT algorithm uses the IPV and VPV of the PV array and gives the MPP and a VDC,REF. This voltage is then passed on to the inverter and then further to the three-phase grid. In this thesis the behaviour of the active and reactive power of the grid which is supplied by the PV array is investigated. The various currents such as inverter current, grid current and load currents are also investigated.
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Sebastian, Sharon. "Grid Connected Photovoltaic Power System with Active Power Filtering." Thesis, 2016. http://ethesis.nitrkl.ac.in/9347/1/2016_MT_SSebastian.pdf.
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The solar energy become a popular and environmental friendly solution for meeting demand of the increasing demand for electric power. The photovoltaic system has now become grid connected system from stand-alone system as it was previously. Now feed in tariff (FIT) has made it a distributed energy (DG) sources in many countries around the world.
The power quality of the grid is being degenerated by the injection of the current by the grid connected PV system with the converters used for DC to AC conversion or the inverter functioning unaware of the harmonics injected by it. Additionally the voltage harmonics is also introduced by the current injected with filtering. Especially the increasing penetration of the DGs in low voltage networks which uses the PV energy as source has had worsened the situation. The rising use of non-linear load has resulted in excessive harmonic pollution resulting in losing of reliability and power quality of the system. Active power filtering can be performed by following various theories one such popular theory is the one using instantaneous power theory proposed and cross vector theory. Other theories like power balance theory and Synchronous reference frame is also effective in APF for distorted and unbalanced supply along with power injection from PV source.
Combining the PV system and APF through a single three phase voltage sourced inverter (VSI) thus making the full utilization of the switching devices at all times is the objective achieved. The PV power is used for the DC voltage regulation and the surplus power from the PV source is also fed through the voltage source inverter (VSI) to the load or the grid. For improving the efficiency single stage conversion is used. Current control is used with reference current generated for both the filtering of harmonics and the MPPT of PV panel and the DC voltage regulation. P&O algorithm with variable perturbation size was used for the efficient tracking of the MPP.
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Qiu, Qing-Zhi, and 邱慶智. "Application of Photovoltaic Power Generation Systems to Reactive Power Compensation." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/72980270753571918784.
Full textAbstract:
碩士國立雲林科技大學
電機工程系
104
Photovoltaic (PV) systems with power electronic interfaces can supply both active and reactive power to grid. This thesis presents the simulation of a single-phase single-stage voltage-mode modulation inverter connected to a single-phase electrical grid. The PV modules are modeled by piecewise linear equivalent circuits. Because of using a single-stage system, the inverter must adjust the DC side voltage to track the maximum power point of PV array. The system compensates the grid with required reactive power according to the request from voltage of the grid. In this way, when the insolation is weak or the PV modules are shaded, the inverter can still be usable to improve the inverter utilisation factor. This thesis presents the EMTP(ElectroMagnetic Transients Program) simulation results of active power, reactive power and apparent power of the inverter output under several different conditions, depending on the insolation level, overvoltage and undervoltage of electrical grid.
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TIEH, CHE-WEI, and 鐵哲瑋. "Module Temperature and Power Model Studies of Photovoltaic Power Systems." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/sbyt47.
Full textAbstract:
碩士健行科技大學
電機工程系碩士班
106
In this thesis, three experimental models, module temperature model, direct current power model and inverter efficiency model, were proposed based on the monitored data of PV systems for purpose of predicting the hourly alternating current power generation. For the part of module temperature, traditional simple module temperature models estimated model temperature based on solar radiation, environmental temperature and PV module specification sheet. It is simple but has big predicting error. In this thesis, a new experimental model was proposed to predict the module temperature based on solar radiation, environmental temperature and wind speed. Its distinguishing feature was extra considering the solar radiation one hour ago. It can predict the module temperature more exactly. For the part of direct current power, traditional simple direct current power models estimated direct current power based on solar radiation, module temperature and module specification sheet. New experimental models were proposed in this thesis to predict the direct current power based on solar radiation and module temperature. There are three regression methods to build the new experimental models. These new models can predict the direct current power more exactly. For the part of inverter efficiency, traditional inverter efficiencies were represented by the highest efficiency or European efficiency. In this thesis, the inverter efficiency was represented by a quadratic equation built based on the monitored data. Through the procedure of model building and data testing by using the monitored data of the 6 PV test systems, when compared with the simple models, it was showed that the proposed experimental model can reduce the predicting error of module temperature from 4.31~5.23℃ to 1.68~3.34℃, reduce the predicting error of direct current power from 9.70% to7.61% and reduce the predicting error of alternating current power from 1.69 % to 0.78%. By combining the three proposed models, an exact integrated model can be built to predict the alternating current powers of PV systems.
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Lee, Ting-peng, and 李天鵬. "Study of Grid-Connected Photovoltaic Power Supply Systems." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/39042409838425038852.
Full textAbstract:
博士國立臺灣科技大學
電子工程系
98
This dissertation aims to study and develop two novel grid-connected photovoltaic (PV) systems. The first PV system is parallel-connected to an electric power grid with a power factor corrector (PFC) for supplying DC loads. The balanced distribution of the power flow between the utility and the PV panels is achieved automatically by regulating the output DC voltage of the PFC. The proposed topology, which can effectively transfer the tracked maximum power from the PV system to the DC load, while the unity power factor is obtained at the utility side. The DC-connected Photovoltaic system has the advantages of high reliability and low cost due to its simple topology and easy control. The conventional AC-connected photovoltaic system consists of a DC/DC converter for tracking the MPP of the photovoltaic panels and a DC/AC inverter for supply AC voltage output. An interesting alternative solution is the application of a single-stage topology. Thus, this dissertation also presents the second PV system that is a single-stage full-bridge inverter topology with maximum power point tracking (MPPT) function. High MPPT accuracy and high conversion efficiency can be achieved by using a simple single-stage configuration. The advantages of the single-stage topology are a high power density, simple configuration and low circuit cost compared with the conventional two-stage structure. The operation principles and design considerations of the proposed DC and AC grid-connected PV systems are discussed and analyzed in details. The laboratory prototypes are implemented and tested. The experimental results are shown to verify the feasibility of the studied schemes.
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Li, Ching-Ju, and 李靜如. "Study on the Power Conditioner of Photovoltaic Systems." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/50325586655055862405.
Full textAbstract:
碩士國立勤益科技大學
電機工程系
97
The purpose of this thesis is to study the power conditioner of a grid connected photovoltaic (PV) system. The studies include a novel maximum power point tracking (MPPT) technique and a power conditioner of islanding phenomenon detection. First, the simulation environment for grid connected PV system is built by using PSIM software package. And the 516W and 3kW PV systems with Kyocera KC40T and Siemens SP75 solar modules are used as examples to finish the simulation of the proposed MPPT and islanding detection methods. The proposed intelligent MPPT algorithm based on the matter-element model and the extended correlation function makes full utilization of PV array output power which depends on solar insolation and ambient temperature. The proposed intelligent MPPT algorithm based on extension theory can automatically adjust the step size to track the PV array maximum power point (MPP) and is able to effectively improve the dynamic response and steady state performance of the PV systems simultaneously. The proposed of islanding phenomenon detection technologies is based on an extension neural network (ENN) for PV system. It combines the extended correlation function of extension theory with learning, recalling, generalize and parallel computing of neural network (NN). Therefore, the proposed technology can correctly differentiate the islanding operation of a PV system and then to disconnect the load from inverter, even the power quality problems exist. Finally, some simulation results are made to demonstrate the validities of the proposed extension MPPT method and the extension neural network based islanding detection method for a power conditioner of PV systems.
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Chen, Chia-Chen, and 陳加振. "Development of Photovoltaic and Battery Hybride Power Systems." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/57006064902033257307.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
100
This thesis is concerned with the development of a hybrid power supply system which utilizes both photovoltaic energy and storage battery. This system adopts a maximum power tracking control approach for the photovoltaic power system which supplies stable DC voltage, and convertes it to single-phase voltage via a full-bridge DC-DC power converter, thereby completing the basic structure of the grid-connected system. The angular position of the grid can be detected and the data can be used in the quadratic-direct axis current closed-loop control strategy to realize the control of the grid-connected system. When the photovoltaic energy is insufficient to sustain the grid-connected system, the energy balance of the overall system can be achieved by utilizing battery which are capable of storing and releasing energy. In the thesis, a signal processing device , DSP, TMS320F28035 , is used as the control core. All control strategy are accomplished with software. Not only the digitized control of the system is achieved, but also the reliability and stability of the system is enhanced. The experimental results for solar power system show that a 250W grid-connected system converts a 220V single-phase voltage to 24V and releases energy to 40W battery. The total harmonic distortion of the current is 5.25%. As for the battery storage system, a 280W grid-connected system converting a single-phase 220V voltage to 24V is also designed. The total harmonic distortion of the current is 4.37%. The overall power conversion efficiency reaches 75%. The experimental results have verified the feasibility and control strategy of the proposed system.
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Sahu, Pradeep Kumar. "Sliding Mode Control of Photovoltaic Energy Conversion Systems." Thesis, 2016. http://ethesis.nitrkl.ac.in/8197/1/2016_Phd_Pradeep_511EE701_Sliding.pdf.
Full textAbstract:
Increasing interest and investment in renewable energy give rise to rapid development of high penetration solar energy. The focus has been on the power electronic converters which are typically used as interface between the dc output of the photo voltaic (PV) panels and the terminals of the ac utility network. In the dual-stage grid-connected PV (GPV) system, the dc dc stage plays a significant role in converting dc power from PV panel at low voltage to high dc bus voltage. However, the output of solar arrays varies due to change in solar irradiation and weather conditions. More importantly, high initial cost and limited lifespan of PV panels make it more critical to extract as much power from them as possible. It is, therefore, necessary one to employ the maximum power point tracking (MPPT) techniques in order to operate PV array at its maximum power point (MPP). A fast-and-robust analog-MPP tracker is thus proposed by using the concepts of Utkin’s equivalent control theory and fast-scale stability analysis. Analytical demonstration has also been presented to show the effectiveness of the proposed MPPT control technique. After the dc stage, the dc-ac inverter stage is employed to convert dc power into ac power and feed the power into the utility grid. The dc-ac stage is realized through the conventional full-bridge voltage source inverter (VSI) topologies. A fixed frequency hysteresis current (FFHC) controller, as well as an ellipsoidal switching surface based sliding mode control (SMC) technique are developed to improve the steady state and dynamic response under sudden load fluctuation. Such a control strategy is used not only maintains good voltage regulation, but also exhibits fast dynamic response under sudden load variation .Moreover, VSI can be synchronized with the ac utility grid. The current injected into the ac grid obeys the regulations standards (IEEE Std 519 and IEEE Std 1547)and ful fills the maximum allowable amount of injected current harmonics. Apart from that, controlling issues of stand-alone and grid-connected operation PV have also been discussed. A typical stand-alone PV system comprises a solar array and battery which is used as a backup source for power management between the source and the load .A control approach is developed for a 1-_ dual-stage transformer less inverter system to achieve voltage regulation with low steady state error and low total harmonic distortion (THD) and fast transient response under various load disturbances. The SMC technique is employed to address the power quality issues. A control technique for battery charging and discharging is also presented to keep the dc-link voltage constant during change in load demand or source power. This battery controller is employed for bidirectional power flow between battery and dc-link through a buck-boost converter in order to keep the input dc voltage constant. The robust stability of the closed-loop system is also analyzed. Finally, modeling and control of a 1-_ dual-stage GPV system has been analyzed. A small-signal average model has been developed for a 1-_ bridge inverter. The proposed controller has three cascaded control loops. The simulation results and theoretical analysis indicate that the proposed controller improves the efficiency of the system by reducing the THD of the injected current to the grid and increases the robustness of the system against uncertainties.