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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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Di, Tullio Luccas. "Optimization of a grid-tied inverter : an application-oriented for designing multilevel converters". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/58542.
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Recent developments in energy systems, including the rapid adoption of renewable energy sources and expansion of microgrids have been introducing new challenges and opportunities for the power electronics industry. Of particular interest to this thesis is the increase of grid-connected DC systems. As a means to reduce cost of copper infrastructure these systems favour the utilization of higher DC link voltages. To accommodate higher voltages, a variety of multilevel converters have been proposed, which generally can be built without specialized components, present lower dV/dt losses and synthesize AC signals with better power quality.
Irrespective of the application, the power electronics industry has traditionally relied on generic rules and practices to quickly design converters. Rarely does the development cycle allow for thorough investigation of the converter design, which could enhance performance and give an edge over competitors. This thesis proposes using optimization techniques to aid power electronics engineers in the design of multilevel converters.
The Neutral Point Clamped (NPC) with its variant the Active NPC (ANPC) were selected for the exercise presented. Chapter 2 of this thesis explains the operation and modulation of the topologies. From the analysis, the conduction and switching losses of each device can be predicted. A description of three semiconductor technologies is presented with their characteristics and source of losses. Lastly an equation to size the filter inductor is introduced. All this information is packaged into a model used in the optimization.
Chapter 3 introduces the optimization strategy. Given the complex nature of power electronics, four objective functions were adopted: efficiency, loss distribution, inductance and cost. These functions were combined through a weight system which allows priorities to be asserted. Next, design variables are introduced along with their respective impacts on the objective functions.
Experiments performed with a hardware platform showed the model closely predicts the impact of the design variables on the objective functions. Confident in the model, the optimization was carried out for various scenarios. Single objective optimization led to converters that excel in one aspect but were often not practical. When optimizing with multiple objectives a good compromise was reached with a practical converter.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
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Liu, Qing. "Control of grid-tied inverters for nano-grids". Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422338.
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In recent times, with the development of renewables, the concept of micro-grid emerged, representing a novel bottom up power distribution organization. The micro-grid can integrate the nearby distributed, and mostly renewable, energy sources, the storage devices and the loads into the grid, with increased efficiency, flexibility and reliability, showing significant economical and environmental benefits. The micro-grid concept can be further scaled down to the range of a single house or small building, and differentiated by a new terminology, nano-grid. The proposal of the nano-grid concept is aimed at simplifying the application scenarios, so that a hierarchical bottom-up power distribution network can be established, where the nano-grid plays the lowest-end role. It can not only operate autonomously, feeding the typical household appliances from the available renewable sources; thanks to the modular smart grid architecture, it can also be conveniently interconnected to other similar units, operating in parallel and harmoniously energizing a larger region in a city, a small-island or a village. In addition, the nano-grid also has the possibility of self-integrating into the utility grid, exchanging power with the mains when needed, thanks to a specifically designed grid interface converter. Referring to the latter, a variety of requirements are defined by applicable standards, in terms of load power quality, grid support functionalities, abnormal condition ride-through and protection means.
The realization of the above functionalities is heavily dependent on the control of the grid interfacing inverter hosted within the nano-grid, about which numerous solutions have been proposed in the existing literature. However, few of them can realize all the functionalities simultaneously in a single controller. The target of this dissertation is therefore proposing, analyzing and testing a high-quality, multi-functional control scheme for grid-tied inverters.
This goal is reached in three steps: i) a deep literature review, ii) the identification, study and realization of the multi-functional inverter controller, and iii) the implementation of further, higher level functionalities, like the grid-supporting and parallel operation capabilities.
Accordingly, the study is initiated from step i), with an overview of existing control strategies and key functionalities of grid-tied inverters. The comprehensive review of a research topic is, in any case, very advantageous to define the state of the art solutions and to evaluate the margins for improvement in the existing technology. In this research case, it allowed to understand that a triple-loop controller structure is the most suitable to achieve high-performance control of the nano-grid electrical system and the most promising as to the capability of implementing multiple interface and protection functionalities jointly. In the second step ii), a large-bandwidth triple-loop controller is proposed, whose implementation is the first contribution of this dissertation. The peculiarity of the proposed controller is the large-bandwidth control of the injected grid current, which brings in many beneficial features. Leveraging on this controller organization, multiple functionalities are later implemented by means of a superimposed flexible mode-transition manager and an auto-tuner, altogether forming a high quality, multi-functional control scheme for grid-tied inverters. This represents the second contribution delivered by this dissertation. Finally, in step iii), the extended scenario of multiple parallel-connected grid-tied inverters is discussed, targeting the realization of distributed grid-supporting functionalities in grid-tied mode and the automatic balanced power sharing in parallel-islanded mode. The final implemented control scheme provides a feasible solution for the forthcoming smart nano-grids and represents the third contribution of this research activity.
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Zhao, Zheng. "High Efficiency Single-stage Grid-tied PV Inverter for Renewable Energy System". Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/27520.
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A single-phase grid connected transformerless photovoltaic (PV) inverter for residential application is presented. The inverter is derived from a boost cascaded with buck converter along with a line frequency unfolding circuit. Due to its novel operating modes, high efficiency can be achieved because there is only one switch operating at high frequency at a time, and the converter allows the use of power MOSFET and ultra-fast reverse recovery diode. This dissertation begins with theoretical analysis and modeling of this boost-buck converter based inverter. And the model indicates small boost inductance will leads to increase the resonant pole frequency and decrease the peak of Q, which help the system be controlled easier and more stable. Thus, interleaved multiple phases structure is proposed to have small equivalent inductance, meanwhile the ripple can be decreased, and the inductor size can be reduced as well. A two-phase interleaved inverter is then designed accordingly.
The double-carrier modulation method is proposed based on the inverterâ s operation mode. The duty cycle for buck switch is always one if the inverter is running in boost mode. And the duty cycle for boost switches are always zero if the inverter is running in buck mode. Because of this, the carrier for boost mode is stacked on the top of the carrier for buck mode, as a result, there is no need to compare the input and output voltage to decide which mode the inverter should operate in. And the inverter operates smoothly between these two modes. Based on similar concept, three advanced modulation methods are proposed. One of them can help further improve the efficiency, and one of them can help increase the bandwidth and gain, and the last one takes the advantage of both.
Based on similar concept, another three dual-mode double-carrier based SPWM inverters are proposed. With both step-up and step-down functions, this type of inverter can achieve high efficiency in a wide range because only one switch operates at the PWM frequency at a time.
Finally, the simulation and experiment results are shown to verify the concept and the tested CEC (California Energy Commission) efficiency is 97.4%. It performs up to 2% more efficiently better than the conventional solution.Ph. D.
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Abdelrazek, Ahmed Abdelhakim Moustafa. "Transformerless Grid-Tied Impedance Source Inverters for Microgrids". Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427190.
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Renewable energy source (RESs) diffusion into the power system is continuously increasing, where the world cumulative installed capacity of solar and wind energy sources increased from around 63.2 GW in 2005 to around 903.1 GW in 2017 according to International Renewable Energy Agency (IRENA). The energy utilization from these RESs implies the use of what is called power conditioning stage (PCS). Such PCS acts as an interfacing layer between the RES side and the customer side, i. e. the load or the grid. These PCSs can utilize many different configurations depending on the employed RES, where the two-stage architecture is commonly used with solar photovoltaic (PV) systems due to the low or variable output voltage. Such two-stage architecture is usually implemented using a boost converter in order to regulate the PV source output voltage and maximize the output power, and a voltage source inverter (VSI) in order to achieve the inversion operation. On the other hand, impedance source inverters represent a different family of the existing PCSs, which are called single-stage power converters as they embraces the boosting capability within the inversion operation. This family of PCSs is seen as an interesting and competitive alternative to the twostage configuration, which are mandatory for low or variable voltage energy sources, such as PV and fuel cell energy sources. Therefore, these impedance source inverters have been utilized in many different applications, such as distributed generation and electric vehicles.
This family of PCSs, i. e. impedance source inverters, has experienced a fast evolution during the last few years in order to replace the conventional two-stage architecture since the first release of the three-phase Zsource inverter (ZSI) in 2003. Consequently, many research activities have been established in order to improve the ZSIs performance from different perspectives, such as overall voltage gain, voltage stresses across the different devices, continuity of the input current, and conversion efficiency.
Among these different topological improvements, the conventional ZSI and the quasi-ZSI (qZSI), are the most commonly used structures. Accordingly, the objective of this thesis is to study and reinforce the performance of this family of PCSs. Hence, the work in this thesis starts first by addressing the challenges behind eliminating the low frequency transformer in grid-tied PV systems in order to improve the conversion system efficiency, where a new measurement technique for the dc current component is proposed in order to effectively mitigate this dc current component. Then, the performance of the classical impedance source inverters has been assessed by studying all the possible modulation schemes and proposing a new one, under which the efficiency of these classical impedance source inverters have been improved. Furthermore, the partial-load operation of these impedance source inverters, considering the three-phase qZSI, has been studied and the possible ways of achieving a wide range of operation have been investigated.
Due to the seen demerits behind the classical impedance source inverters, an alternative new topology, which is called split-source inverter (SSI), is proposed, under which these demerits have effectively been mitigated or eliminated. Then, the challenges behind grid-tied operation of this single-stage dc-ac power converters has been investigated considering the SSI topology. It is worth to note that all the prior mentioned contributions have been validated experimentally.
Finally, this thesis is divided into two chapters, where the first chapter introduces an extended summary of the work done concerning the thesis topic, while the second part includes some selected papers from the publications that have been developed during the doctoral study. These selected papers give all the details of the work done in each section in the extended summary.
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Photong, Chonlatee. "A current source inverter with series AC capacitors for transformerless grid-tied photovoltaic applications". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13128/.
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The Current Source Inverter (CSI) is one of the simplest power converter topologies that can convert DC to AC and feed power generated from photovoltaic (PV) cells into the AC grid with a single power conversion stage over the whole PV voltage range. The CSI also provides smooth DC current which is one of the requirements of the PV cells as well as preventing reverse current using unidirectional switches. However, the CSI operates with low efficiency at lower PV voltages, which is where the PV cells produce maximum output power. This low efficiency is caused by large differences in voltage levels between the PV side and the grid side across the converter. This thesis presents an alternative topology to the three-phase CSI by connecting an AC capacitor in series with each AC phase line of the CSI circuit. The presence of the series AC capacitors in the CSI topology allows the AC voltage levels to be adjusted to match the voltage levels of the PV cells. Therefore, the CSI with series AC capacitors is able to operate with optimal DC-AC voltage levels. Performance of the proposed topology is evaluated in comparison to the standard CSI and five other converter topologies based on transformerless circuit concepts selected from those already available in the market and suitable converters discussed in the literature. All converter topologies were modeled and simulated with the SABER simulation software package. The CSI with series AC capacitors prototype was constructed in order to validate the feasibility of the proposed topology and the performance of the proposed topology in comparison to the standard CSI. Simulation results show that the CSI with series AC capacitors provides improved efficiency and better input/output power quality in comparison to the standard CSI. The proposed topology also achieves the lowest output line current distortion, lowest voltage stress across the circuit components and lowest estimated cost of power semiconductors when compared to all considered topologies. Experimental results are also presented to validate the simulation results.
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Eldridge, Christopher Sean. "Using super capacitors to interface a small wind turbine to a grid-tied micro-inverter". Thesis, Kansas State University, 2011. http://hdl.handle.net/2097/8754.
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Master of ScienceDepartment of Electrical Engineering
William B. Kuhn
During the development of an educational renewable energy production platform, it was found that there were no low-cost, efficient grid-tie interfaces for a 160 W DC wind turbine. Typically, a small DC wind turbine is used in conjunction with a rechargeable battery bank or, if the wind turbine is directly interfaced with a grid-tie inverter, a regulator with a diversion-load. The use of batteries is undesirable due to their high-cost and high-maintenance characteristics. Diversion loads by nature waste power, as any excess energy that cannot be accepted by a battery or inverter is usually converted into heat through a resistive element. Initially, a 24 V DC, 160 W Air Breeze small wind turbine was directly connected to an Enphase Energy M190 grid-tie micro-inverter. The 24 V DC Air Breeze wind turbine is designed to charge a battery or bank of batteries while the M190 micro-inverter is designed to convert the DC output of a 200 W solar panel to grid-tied AC power. As expected, the power-production response time associated with the small wind turbine and the power-accepting, load-matching response time of the micro-inverter were not compatible. The rapidly changing power output of the small wind turbine conflicted with the slow response time of the micro-inverter resulting in little power production. Ultimately, the response time mismatch also produced sufficiently large voltage spikes to damage the turbine electronics. In this thesis, a solution for a low-cost, efficient grid-tie interface using no batteries and no diversion load is presented. A capacitance of eight Farads is placed in parallel with the small wind turbine and the micro inverter. The large capacitance sufficiently smoothes the potential abrupt voltage changes produced by the wind turbine, allowing the micro-inverter adequate time to adjust its load for optimal power conversion. Laboratory experiments and data from an implementation of such a parallel super capacitor wind turbine to grid-tie micro-inverter configuration are provided along with DC and AC power production monitoring circuits interfaced with a micro controller.
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Johnson, Benjamin Anders. "Modeling and Analysis of a PV Grid-Tied Smart Inverter's Support Functions". DigitalCommons@CalPoly, 2013. https://digitalcommons.calpoly.edu/theses/994.
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The general trends in the past decade of increasing solar cell efficiency, decreasing PV system costs, increasing government incentive programs, and several other factors have all combined synergistically to reduce the barriers of entry for PV systems to enter the market and expand their contribution to the global energy portfolio. The shortcomings of current inverter functions which link PV systems to the utility network are becoming transparent as PV penetration levels continue to increase. The solution this thesis proposes is an approach to control the inverters real and reactive power output to help eliminate the problems associated with PV systems at their origin and in addition provide the grid with ancillary support services. The design, modeling, and analysis of a grid-tied PV system was performed in the PSCAD software simulation environment. Results indicate that in the presence of grid disturbances the smart inverter can react dynamically to help restore the power system back to its normal state. A harmonic analysis was also performed indicating the inverter under study met the applicable power quality standards for distributed energy resources.
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Alskran, Faleh A. "Dynamic modeling and analysis of the three-phase voltage source inverter under stand-alone and grid-tied modes". Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18220.
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Master of ScienceDepartment of Electrical and Computer Engineering
Behrooz Mirafzal
Increasing energy demand, rising oil prices, and environmental concerns have forced attention to alternative energy sources that are environmentally friendly and independent of fossil fuels. Renewable energy sources (RES) have become an attractive alternative to the traditional energy sources for electric power generation. However, one of the main challenges of RES adaption arises when connecting RES to the electric grid. Voltage source inverters (VSIs), typically, connect RES to the electric grid. Similar to any engineering system, detailed dynamic models of the VSIs are needed for design and analysis purposes. However, due to the non-linearity of VSIs, development of dynamic models that can accurately describe their behavior is a complex task. In this thesis, a detailed averaged-state-space model of the two-level three-phase space vector pulse width modulation VSI and its companion LCL filter is derived. Because VSIs can operate under stand-alone and grid-tied modes, two models were derived for each case. In the derived models, the VSI modulation index m and phase angle ϕ are initially considered constant. In practice, however, these parameters are considered the main control parameters. To model these parameters as control inputs, small-signal models of the VSI under stand-alone and grid-tied modes were derived. To verify the accuracy of the developed large-signal and small-signal models, Matlab/Simulink simulations were carried out. The simulation results were compared against the models results. Moreover, the models were verified through lab experiments. The developed models can be used as design and analysis tools. In addition, the developed models can be used as fast and efficient simulation tools for system studies, when the modeling of switching transients is not needed. Nowadays, the number of VSIs connected to the electric grid is growing exponentially. The amount of time and computation needed to simulate VSIs using simulation software packages can be significantly decreased by the use of the developed models.
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Khlid, Ben Hamad. "Fuel cell power conditioning multiphase converter for 1400 VDC megawatts stacks". Thesis, Cape Peninsula University of Technology, 2019. http://hdl.handle.net/20.500.11838/3042.
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Thesis (PhD (Electrical Engineering))--Cape Peninsula University of Technology, 2019Energy systems based on fossil fuel have demonstrated their abilities to permit economic development. However, with the fast exhaustion of this energy source, the expansion of the world energy demand and concerns over global warming, new energy systems dependent on renewable and other sustainable energy are gaining more interests. It is a fact that future development in the energy sector is founded on the utilisation of renewable and sustainable energy sources. These energy sources can enable the world to meet the double targets of diminishing greenhouse gas emissions and ensuring reliable and cost-effective energy supply. Fuel cells are one of the advanced clean energy technologies to substitute power generation systems based on fossil fuel. They are viewed as reliable and efficient technologies to operate either tied or non-tied to the grid to power applications ranging from domestic, commercial to industrial. Multiple fuel cell stacks can be associated in series and parallel to obtain a fuel cell system with high power up to megawatts. The connection of megawatts fuel cell systems to a utility grid requires that the power condition unit serving as the interface between the fuel cell plant and the grid operates accordingly. Different power conditioning unit topologies can be adopted, this study considers a multilevel inverter. Multilevel inverters are getting more popularity and attractiveness as compared to conventional inverters in high voltage and high-power applications. These inverters are suitable for harmonic mitigation in high-power applications whereby switching devices are unable to function at high switching frequencies. For a given application, the choice of appropriate multilevel topology and its control scheme are not defined and depend on various engineering compromises, however, the most developed multilevel inverter topologies include the Diode Clamped, the Flying Capacitor and the Cascade Full Bridge inverters. On the other hand, a multilevel inverter can be either a three or a five, or a nine level, however, this research focuses on the three-level diode clamped inverters. The aim of this thesis is to model and control a three-level diode clamped inverter for the grid connection of a megawatt fuel cell stack. Besides the grid, the system consists of a 1.54 MW operating at 1400 V DC proton exchange membrane fuel cell stack, a 1.26 MW three-level diode clamped inverter with a nominal voltage of 600 V and an LCL filter which is designed to reduce harmonics and meet the standards such as IEEE 519 and IEC 61000-3-6. The inverter control scheme comprises voltage and current regulators to provide a good power factor and satisfy synchronisation requirements with the grid. The frequency and phase are synchronised with those of the grid through a phase locked loop. The modelling and simulation are performed using Matlab/Simulink. The results show good performance of the developed system with a low total harmonic distortion of about 0.35% for the voltage and 0.19% for the current.
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Crisafulli, Vittorio Claudio. "Analysis and Development of new strategies for solar energy conversion: New systems of integration, topologies and control". Thesis, Università degli Studi di Catania, 2011. http://hdl.handle.net/10761/226.
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In the recent past, energy and environment have played opposite roles in human progress.
Energy has been as an engine for the development and the environment has been as the
breaker of it.
Only after a more conscious and rigorous international policy on environment protection,
not opposed to the development, energy and environmental matters have become unified
behind a new sustainable model. This has determined new strategies in the energy sector.
Hence, renewable sources have become a must in this new sustainable model.
The key role in the last decade has been played by the Distributed Power Generation Systems
(DPGS) which present an efficient and economic way of generating electricity closer to
the load(s). The DPGS can contribute to an efficient and renewable electricity future by
potentially: increasing the use of renewable sources of energy; improving the efficiency of the
electricity system by reducing transmission and distribution losses; improving the security of
the electricity supply through increased diversity of supply and reduced vulnerability to
simultaneous system failures. However, the new trend of using DPGS comes also with a suite
of new challenges. One of the challenges is the interaction between the DPGS and the utility
grid. As a consequence, grid interconnection requirements applied to the distributed generation
are continuously updated in order to maintain the quality and the stability of the utility
grid.
Consequently, the major tasks of this thesis were to analyze and to develop new strategies
for solar energy conversion addressing efficiency and quality in order to allow the DPGS not
only to deliver power with high efficiency to the utility grid but also to sustain it.
This thesis was divided into three main parts, as follows: à ¢ Small Photovoltaic System:
AC moduleà ¢ , à ¢ Control of DPGSà ¢ and à ¢ New Topologies and Devices, technologies for
multilevel inverter addressing grid connectionà ¢ .
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In the first part, the main focus was on topologies for module integration. Additionally, a
new topology has been proposed and developed and successfully tested.
In the second part, the main focus was c on Control, PWM techniques and ancillary function
as grid-connection algorithms.
In the third part, the main reported research was concentrated around the role of multilevel
inverter in the next future of DPGS. Focusing on topologies and technologies device.
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Ekström, Rickard. "Offshore Marine Substation for Grid-Connection of Wave Power Farms : An Experimental Approach". Doctoral thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-229191.
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Wave power is a renewable energy source with great potential, which is why there are more than a hundred ongoing wave power projects around the world. At the Division of Electricity, Uppsala University, a point-absorber type wave energy converter (WEC) has been proposed and developed. The WEC consists of a linear synchronous generator placed on the seabed, connected to a buoy floating on the surface. Power is absorbed by heave motion of the buoy, and converted into electric energy by the generator. The point-absorber WEC must be physically much smaller than the wavelength of the incoming waves, and can therefore not be scaled to very high power levels. Instead, the total power output is boosted by increasing the number of WECs, connecting them in wave power farms. To transfer the electric energy to the grid, an intermediate marine substation is proposed, where an AC/DC/AC conversion step is performed. Within this PhD-work, a full-scale offshore marine substation has been designed, constructed and experimentally evaluated. The substation is rated for grid-connection of seven WECs to the local 1kV-grid, and is placed on the seabed 3km off the coast at a depth of 25m. Various aspects of the substation design have been considered, including the mechanical and electrical systems, the WEC electrical interface, offshore operations and the automatic grid connection control system. A tap change circuit and different multilevel topologies have also been proposed. This dissertation has an experimental approach, validating a major part of the work with lab results. The final substation electrical circuit has been tested at rated grid voltage with a fluctuating input power source. The efficiency has been measured and the implemented functions are verified. Offshore operations have been successfully carried out and offshore wave farm data is expected in the nearby future.
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Komlanvi, Moglo. "Computer aided design of 3D of renewable energy platform for Togo's smart grid power system infrastructure". Thesis, University of Derby, 2018. http://hdl.handle.net/10545/623021.
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The global requirement for sustainable energy provision will become increasingly important over the next fifty years as the environmental effects of fossil fuel use become apparent. Therefore, the issues surrounding integration of renewable energy supplies need to be considered carefully. The focus of this work was the development of an innovative computer aided design of a 3 Dimensional renewable energy platform for Togo’s smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications. The Wind, Hydro, and PV system forming our 3 Dimensional renewable energy power generation systems introduces a new path for hybrid systems which extends the system capacities to include, a stable and constant clean energy supply, a reduced harmonic distortion, and an improved power system efficiency. Issues requiring consideration in high percentage renewable energy systems therefore includes the reliability of the supply when intermittent sources of electricity are being used, and the subsequent necessity for storage and back-up generation The adoption of Genetic algorithms in this case was much suited in minimizing the THD as the adoption of the CHB-MLI was ideal for connecting renewable energy sources with an AC grid. Cascaded inverters have also been proposed for use as the main traction drive in electric vehicles, where several batteries or ultra-capacitors are well suited to serve as separate DC sources. The simulation done in various non-linear load conditions showed the proportionality of an integral control based compensating cascaded passive filter thereby balancing the system even in non-linear load conditions. The measured total harmonic distortion of the source currents was found to be 2.36% thereby in compliance with IEEE 519-1992 and IEC 61000-3 standards for harmonics This work has succeeded in developing a more complete tool for analysing the feasibility of integrated renewable energy systems. This will allow informed decisions to be made about the technical feasibility of supply mix and control strategies, plant type, sizing and storage sizing, for any given area and range of supply options. The developed 3D renewable energy platform was examined and evaluated using CAD software analysis and a laboratory base mini test. The initial results showed improvements compared to other hybrid systems and their existing control systems. There was a notable improvement in the dynamic load demand and response, stability of the system with a reduced harmonic distortion. The derivatives of this research therefore proposes an innovative solution and a path for Togo and its intention of switching to renewable energy especially for its smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications.
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Yang, Zhiqing [Verfasser], Doncker Rik W. [Akademischer Betreuer] De i Frede [Akademischer Betreuer] Blaabjerg. "On the stability of three-phase grid-tied photovoltaic inverter systems : modeling, investigation, and stability-enhanced operation / Zhiqing Yang ; Rik W. de Doncker, Frede Blaabjerg". Aachen : Universitätsbibliothek der RWTH Aachen, 2021. http://nbn-resolving.de/urn:nbn:de:101:1-2021081007552125199862.
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Algarny, Khalil Saad A. "The development of three-phase cascaded h-bridge multilevel inverter with DC-side sensor-less control for applications of independent MPPT photovoltaic and battery grid-connected systems". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/207283/1/Khalil%20Saad%20A_Algarny_Thesis.pdf.
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The utilization of solar energy has grown exponentially in the past years mainly due to environmental concerns. Finding ways to reduce the cost of solar energy systems and their complexity are of great importance. Among the key achievements of this project are, designing an efficient and economical photovoltaic system architecture, introducing DC-link voltage estimation to the three-phase PV system based multilevel-inverter, introducing PV current estimation to the three-phase PV system based multilevel-inverter, achieving phase balancing by injecting zero-sequence voltage utilizing the estimated values and achieving battery SOC balancing using the estimation algorithm. The proposed methods were justified using simulations.
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Olímpio, Filho José de Arimatéia. "Conversor multifuncional conectado à rede elétrica para compensação de oscilações de potência instantânea /". Bauru, 2019. http://hdl.handle.net/11449/191227.
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Orientador: Helmo Kelis Morales ParedesResumo: Esta dissertação de mestrado propõe o desenvolvimento e a implementação de uma estratégia de compensação para conversores eletrônicos de potência (CEP) multifuncionais conectados à rede elétrica. A geração dos sinais de referência de corrente para o conversor multifuncional é obtida através das grandezas conservativas da CPT, do inglês Conservative Power Theory. O CEP proposto neste trabalho desempenha o papel de um conversor interface de rede no modo conectado, tendo como finalidade a mitigação de oscilações de potência instantânea bem como injeção de potência ativa na rede elétrica, caracterizando assim o seu aspecto multifuncional. São realizados estudos teóricos e simulações computacionais com o intuito de validar a estratégia proposta. Para tanto, foram identificadas as parcelas indesejadas de corrente que permitam a compensação das componentes oscilatórias da potência instantânea e da energia reativa instantânea da CPT. O CEP é controlado em modo corrente, através da estratégia de modulação PWM com duas malhas de controle. A estratégia de compensação e o sistema de controle serão avaliados e testados via simulação para diferentes configurações de cargas, incluindo uma carga não-linear desbalanceada operando em condições onde as distorções e desequilíbrios de tensão sejam consideráveis. Por fim, resultados experimentais obtidos com um protótipo em escala laboratorial são utilizados para validar a estratégia de compensação proposta
Abstract: This master’s thesis proposes the development and implementation of a compensation strategy for the three-phase multifunctional grid-tied inverter. The reference signal generation method for grid-tied is based on the Conservative Power Theory (CPT). In this work, the multifunctional inverter plays the role of the Utility Interface (UI) which perform several functions: in grid-connected operation, it injects active power into the grid and compensates the instantaneous power oscillation and the instantaneous reactive energy oscillation. The goal is to execute theoretical studies and computational simulations to validate the proposed strategy. For this purpose, firstly are identifies the unwanted currents which allow the compensation of the oscillatory terms of instantaneous power and reactive energy. The inverter is controlled in current mode through PWM modulation strategy with two control loops. In addition, the proposed compensation strategy and control system is evaluated and tested for different load configurations, such as linear and nonlinear loads (balanced and unbalanced) operating under different voltage conditions (distorted and unbalanced). Finally, experimental results are presented to validate the effectiveness and performance of the proposed compensation strategy.
Mestre
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Huang, Wei Che, i 黃偉哲. "Design of Cascadable Grid-Tied Multilevel Inverter Modules for High Voltage Applications". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/485e35.
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Banavath, Satish Naik. "A New Class of Single DC-link Fed Multilevel Inverter Topologies for Grid Connected Photovoltaic Systems with Reduced Component Count and Inherent Capacitor Balancing". Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4203.
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Grid integration of photovoltaic (PV) energy sources has been mostly governed by conventional two-level voltage source inverters. These topologies have significant switching power losses, dV/dt stress and THD level at lower switching frequencies. The above issues can be solved by introducing more voltage levels through multilevel converters. Conventional multilevel converters have many issues like neutral point voltage drift in neutral point clamped (NPC) topology, floating capacitor charge balance in flying capacitor (FC) topology and large number of isolated DC sources in cascaded half bridge (CHB) topology when scaling them for higher number of voltage levels. Additionally, active power devices and its associated gate drivers, clamping diodes, flying capacitors and DC link capacitors also increase with levels. Hence, it is desirable to generate a multilevel voltage output with a single DC link and with the reduced components count. This thesis proposes a new way of generating multilevel voltage output using a single DC source and with the least components count. The thesis also proposes a new gate driver that can be operated at wide duty cycle ratios and wide band frequency.
The thesis presents five major contributions as follows,
1. 16 switch five level inverter for isolated grid tied systems
2. 12 switch five level inverter for isolated grid tied systems
3. Inherent DC link capacitor balancing
4. Extension of five level inverter topologies to higher levels
5. A Wide duty cycle range wide band high frequency isolated gate driver for multilevel power converters
First part of the research work, presents a novel five level inverter for high power isolated grid connection, which is powered by a single DC source. The proposed topology employs overall 16 active power devices, two DC link capacitors and a Scott-T transformer. Out of 16 power switches, 8 switches operate at high frequency and remaining 8 operate at the fundamental frequency. The DC link capacitors have an inherent voltage balancing which eliminates the requirement of charge balancing circuit or complex control algorithm. Additionally, necessity of expensive voltage sensors are also mitigated. The five level converter initially generate five level voltages in two phase system, and then they are transformed to three phases by using a Scott-T transformer. Operation of the proposed five level inverter (1 kW) is tested experimentally by connecting it to a three phase grid with unity power factor control. Second part follows the footsteps of the first topology.
The second topology presents a grid connected five level inverter with only 12 power devices. This topology is also powered by a single DC source. Eight (8) out of 12 power devices are switched at fundamental frequency (variable) and the remaining devices are switched at high frequency. The proposed inverter is validated experimentally by connecting it to a three phase grid. The performance of capacitor voltage balancing under steady state and transient loading conditions is verified.
Third part of the thesis discusses about the inherent charge balancing phenomenon of the DC link capacitors for the proposed inverter topologies. In both the topologies, the DC link capacitors have inherent voltage balancing capability. This feature eliminates the requirement of voltage sensors and complex control schemes which are generally employed in the conventional multilevel inverters.
In fourth part of the research work, a wide band frequency and wide duty cycle operated isolated gate driver with only a single auxiliary power supply is proposed. The proposed gate driver is specifically advantageous for multilevel inverters as all the gate drivers can be powered by a single auxiliary power supply. The integrated gate driver has features like, wide duty cycle (0 - 100%) and wide band frequency (ranging from DC to 1 MHz) operation, short circuit/over current, and miller clamp protections. The performance of the gate driver is validated experimentally followed by a LTSPICE software simulations.
Finally, a generalized multilevel inverter topology based on the proposed five level inverter topologies with only a single DC source is presented. Multilevel output is obtained by cascading H-bridge modules on either side of the five level converter after the unfolding stage. Connecting `n' number of H-bridge modules per phase to the five level converter leads to [8n+1] levels of the output voltage. Feasibility of the converter is validated by testing a nine level inverter configuration. The proposed concept uses least active power devices, DC link capacitor, flying capacitor, and diodes compared to the existing single DC link fed multilevel inverter topologies.
All the above presented topologies and circuits are extensively tested in simulation and in the experimentation in laboratory for three phase grid connected unity power factor operation. A 1 kW, 50 Hz fundamental and 10 kHz switching inverters was developed for the experimental studies. The inverter is used for the grid integration of DC sources with 192 V, 1 kW power rating. The inverter prototype consists of power semiconductor switches of rating 1200 V and 75 A insulated gate bipolar transistor (IGBT) half bridge Semikron modules (SKM75GB12T4). The proposed gate drivers were used to drive the power IGBTs. The Scott-T transformer is realized using two single phase transformers with an appropriate winding turns ratio. The current control and PWM signal generation is carried in a digital signal processor (DSP-TMS320F28335) with a clock frequency of 150 MHz. The grid voltage and currents were sensed by using LEM make voltage (LV-25P) and current (LA-55P) sensors. The sensed voltage and current data is fed to the analog to digital converter (ADC) which internally exists in the DSP. All the computations and frame transformations were also carried within the DSP. The dead time for the IGBT modules is generated as 1μs. The testing was done by connecting the proposed inverters to the grid. The inverter performance is validated at various loading conditions. The inherent capacitor balancing was also validated under steady state and transient loading conditions.
The proposed inverter topologies exhibits advantages like, reduced components count, single DC link operation, inherent capacitor voltage balancing, fundamental switching devices and inherent isolation. Overall size of the proposed inverters is less compared to the conventional five level inverters for grid connected applications where isolation is mandatory. The inherent capacitor voltage balancing also eliminates the requirement of expensive voltage sensors, complex control circuits and algorithms. The fewer active components count results in simple control architecture and improves reliability of the inverters to a large extent. The experimental validation shows that the proposed inverter topologies can be considered as viable solutions for the high power isolated grid tied photovoltaic systems.
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Wu, Chih-Chung, i 吳志崇. "DESIGN AND IMPLEMENTATION OF ELECTRICAL POWER GRID-TIED INVERTER". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/63310047662111139507.
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碩士大同大學
電機工程學系(所)
94
The purpose of this thesis is to develop an inverter with grid-tied that can provide energy to share load with utility grid. The output power of inverter is 300 W and AC 110 Vrms for single phase. A full-bridge inverter with transformer, isolating primary and secondary side which can protect control circuit and avoid being burned when power stage has faults. A DSP of TI TMS320F2812 which is used to control the inverter in this thesis has high speed calculating function and make all control circuits flexible.
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Chou, Yu Ping, i 周右平. "Design of a 10kW Three-Phase Grid-tied Inverter". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/c86phe.
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碩士長庚大學
電機工程學系
104
Inverters in back to back connection are utilized to convert the voltage and frequency of the power source to another format. Typical application of inverters is the wind power system. This study presents a back to back inverter for equal voltage and frequency format conversion. In the back to back inverter, one inverter works to get active power in order to maintain the dc-link voltage, and another inverter returns part of the active power to the power grid. The power grid affords only the power loss of the inverter, which benefits the test of the inverter rated above 10kW under general distribution line. Experimental setups include single inverter reactive power control and back to back inverters active and reactive power controls. Experimental results show that the power returns to the power grid is close to originally put in, and the power capability can achieves 15kW.
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Wang, Chi-Yuan, i 王智源. "Design of Grid-Connected Hybrid Multilevel Inverter". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/bqu3d9.
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碩士國立虎尾科技大學
機械與機電工程研究所
98
This thesis proposed a hybrid multi-level inverters having 3 inverters in series with distinct dc link voltages to generate 13 voltage levels in order to reduce output voltage and current distortion and power switch stress and switching frequency. Therefore, EMI (Electro Magnetic Interference) can be alleviated due to lower switching frequency. The experiments are conducted to show the performance of the proposed hybrid multi-level inverters that in stand-alone system to reduce the voltage distortion significantly in load-variation, rectifier load, and phase-controlled load conditions; for the grid-tied system, the output current is closed to sinusoidal waveform and current ripple is reduced as well.
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Hou, Chia-Shin, i 侯嘉信. "Design and Implementation of Grid-Tied Single-Phase PV Inverter". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/63705105888646940486.
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碩士中原大學
電機工程研究所
99
The purpose of this thesis is to design and realize a gird-tied single-phase PV inverter. A straight-approach maximum power point tracking (SA-MPPT) is adopted to make the PV inverter work at MPP under different insolation. In this thesis, the boost converter can pump energy from the PV module to the PV inverter, in which the PV inverter can adaptively provide proper current with current control to the power utility according to the guidance of the SA-MPPT. The modeling and analysis of the current control in the inverter are conducted in detail. Finally, a prototype of 1kW PV inverter is designed and implemented to assess the predictions. The experimental result is in feasibility close to the estimation.
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Lo, Cheng-Hsiao, i 羅正校. "Design and Implementation of Grid-Tied Inverter with Stationary-Frame Current Control". Thesis, 2011. http://ndltd.ncl.edu.tw/handle/as42w2.
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碩士國立臺北科技大學
電機工程系研究所
99
The object of this thesis is to design and implement a single phase grid-tied DC/AC Inverter. The system is composed of a full bridge inverter with LCL filter and Texas Instruments TMS320F28035 as digital signal processor. The control scheme uses a stationary frame current controller as the unipolar voltage switching pulse-width modulation command. The design specifications are input DC voltage of 200 V, output voltage of 110 Vrms/60 Hz, power rating of 800 W, switching frequency of 12 kHz. Simulation and experimental results verify the control scheme can cope with input DC voltage 200 V and various load conditions, the inverter efficiency is higher than 90%, and the total voltage harmonic distortion is less than 5%.
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Huang, De-Ming, i 黃德銘. "Development of a Grid-Tied Single-Phase Inverter with Programmable Output Power". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/21638543712403084841.
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碩士國立臺灣科技大學
電機工程系
102
In recent years, the rapid industrial development, drastic increase in resource consumption, additional impact of the energy crisis, and the Fukushima Daiichi nuclear disaster, have urged people to focus on the necessity of various alternative energy sources and renewable energy technologies. Traditional electrical grids remain vital because stable new energy sources are still lacking. Thus, because grid-tied systems have become the primary application of new energy systems, discussions on grid-tied control technology are crucial. The objective of this study was to develop a single-phase boost-type forward converter to convert a storage battery voltage of 48 V to 200 V, providing energy to the DC-link side of a DC-AC converter. Additionally, a single-phase full-bridge DC-AC converter was used to connect to the grid side in parallel, transferring energy to the grid to supply loads. To conform to the liberalization of power industries in Taiwan and the contract capacities and unit electricity prices specified by power companies, power outputs to the grid side can be controlled based on electricity demands during various times. This study used a high-performance digital signal processor (TMS320F28335) produced by Texas Instruments as the control core of the overall system. The control strategies for the system were completed using software programs, thus achieving digitized system control to reduce hardware circuitry usage and increase system reliability.
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Purnama, Irwan, i 潘宜銳. "A Simplified Analog Control Method for Grid-Tied Single Phase Boost Inverter". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/03784157335186377222.
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博士國立臺灣科技大學
電子工程系
104
Nowadays, an inverter is purposed to convert and deliver the power from a DC power source to either the AC load or the AC grid. The conversion and integration of DC power source to the grid system become important since most of the renewable power sources are DC voltage source. There are some criteria that should exist in the configured conversion system such as high reliability, compact and low cost. To meet those criteria, two important strategies should be considered i.e. implementing a proper power inverter topology and designing high-performance control method. There are many inverter topologies proposed in many references for single-stage DC/AC power conversion. Differential boost inverter (DBI) is a kind of topology that can boost a lower voltage of the DC power source to a higher AC voltage. Among all the inverter topologies, this topology is very attractive since it is constructed from two bi-directional boost converters. Since each of the converters generates a DC-biased AC voltage, the inverter generates a differential output AC voltage which is obtained from the output voltage difference of the two-converter. In this work, one-cycle control (OCC) method is designed and implemented in a DBI. This control method is preferred to be implemented because of its advantages such as fast dynamic response and better perturbation rejection. Based on the triangle rule of the real-time integrator, OCC can track the variable reference voltage of the power converter. Therefore, the control method has an ability to follows a DC-biased AC voltage reference and to handle the input voltage perturbation. To connect the DBI to the AC grid, a power control shifting phase (PCSP) method is implemented in this work. In this method, the injected grid power is controlled by means of the inverter output voltage shifting phase. The power control is designed to achieve a unity power factor (PF) by implementing a zero reactive power reference so that only active power is injected to the AC grid. Both simulation and experimental have been done to verify that the designed controller can achieve a unity power factor with acceptable THD level.
26
Hsiao, Wei-Min, i 蕭瑋岷. "Design and Implementation of Grid-Tied Micro Inverter with Boundary Conduction Mode". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/23037002455973682660.
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碩士國立聯合大學
電機工程學系碩士班
100
Increasing pressure of the environmental protection and anticipative shortage of the conventional energy has called for the development of the regenerative energy. The solar power due to its inexhaustibility is the most important energy in the foreseeable future. How to utilize the solar energy efficiently and feed it to the grid is an important research topic currently. Not as the conventional large scale PV generation system with a large amoung of PV modules in series, this thesis presents the micro inverter which can feed the PV module power to the grid directly. The proposed inverter is composed of a flyback converter with current source output and a polarity inversion circuit. The variable frequency voltage mode control method are presented to operate the flyback converter in the boundary conduction mode (BCM) and control the output current of the inverter to be sinusoidal and in phase with the grid voltage. Modeling of the inverter and quantitative controller design of the variable frequency voltage mode control method is presented. A 120W experimental system with PV module for generating power is built. The effectiveness of the proposed method is confirmed with some simulation and measured results.
27
Lin, Yi-Te, i 林羿德. "Terminal Sliding Mode Maximum Power Control for Grid-Tied Photovoltaic Inverter Systems". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/40872919786556905989.
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碩士中原大學
電機工程研究所
100
This research presents a grid-tied inverter development for PV power generating systems with MPPT ability. The inverter regulates the output power of the PV array system by terminal sliding mode current tracking control with the MPPT algorithm. To efficiently increase the power tracking performance, we design a terminal sliding mode controller TSMC such that the system guarantees the finite-time convergence of inverter current tracking. Moreover, robustness against parameter uncertainties and disturbances are also considered in the controller design such that the controller is suitable for real implementation. Finally, both simulations and experiments are done to verify the feasibility of the proposed controller. In experiments, a grid-tied PV power generation system is constructed. The MPPT control strategy is implemented by TI DSP TMS320 F28335; therefore, the designed MPPT system not only comes with small size and high reliability, but also is contributive in grid-tied PV power system applications.
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Liao, Hsiang-Yun, i 廖緗芸. "A Study on Grid-tied Modular Inverter Design for Micro-Turbine Generator". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/pk4s6r.
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碩士國立臺南大學
電機工程學系碩博士班
107
This thesis is aimed at researching a modular inverter circuit for micro-turbine power generation system. In the circuit the inverter are divided by basic and extended modules, in which basic module is used to perform power conversion required from micro-turbine generator while extended modules are designated for online redundant services. Through this design, it is not only beneficial to improve the reliability of energy production, but also owns high flexibility of capability extension. Furthermore, a current-sharing scheme as well as a modular inverter arrangement is developed for the achievement of uniform current dispatch of online inverter modules. The method proposed in this thesis was examined under various scenarios. The results help consolidate the feasibility and practicability of the approach for the applications considered.
29
Chen, Yu-Wei, i 陳昱維. "Analysis and Design of Digital Proportional-Integral Compensator for Grid-Tied PV Inverter". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/54862698477882372563.
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碩士中原大學
電機工程研究所
101
This thesis is to realize a single-phase PV inverter driven by using digital-signal-processor-based sinusoidal-pulse-modulation (SPWM) controller. Digital proportional - integral (DPI) compensator is employed for system stability and harmonic suppression, which builds the analysis and design strategy. For system control and compensation, state-averaged analyses for system analysis and MATLAB for system simulation are conducted, respectively. Finally, a demonstrated prototype of 1.5kW PV inverter is realized to verify the theoretical analysis and simulation. Compared to analog proportional-integral (PI) control, the DPI control to the total harmonic distortion (THD) suppression does have good results and easy to implement in real design.
30
Venkatramanan, D. "Modeling, Analysis and Control of Reconfigurable Battery/Grid Tied Solar Photo-Voltaic Inverter". Thesis, 2019. https://etd.iisc.ac.in/handle/2005/5119.
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Grid reliability and power outages are key concerns today, due to the ever-increasing energy
demand. Traditionally, Uninterruptible Power Supplies (UPS) with battery storage have been
employed to contend with grid outages. For renewable power production, Solar-Photovoltaics
(SPV) based Distributed Energy Resources (DERs) have been integrated with the grid using a
power electronic Grid-Tied Inverter (GTI). A typical GTI by design, engages in power conversion only when the grid is present, and ceases operation during a power outage to avoid a local
unintentional island formation. Thus, solar energy is left unutilized by the GTI during a power
outage, where the UPS steps in, to power critical loads. Recently, hybrid-PV or dual-mode
inverter systems, that combine the complementary functional properties of UPS and GTI, have
been in the focus of research due to their ability of standalone system operation during an
outage while accessing solar power. Such a hybrid approach, although meets the desired operational objectives, requires the design, sizing, and control of the entire system, that comprises
of multiple power converters, battery-banks, and SPV, to be carried out in a unified manner.
This work enhances the existing methods of solar energy access during a power outage,
where the GTI is kept as an independent system from the UPS. A reconfigurable battery/grid
tied inverter (RBGTI) scheme is proposed, that ties to the grid and functions as a regular DCAC GTI when grid is present. However, during a power outage, it reconnects to the batterybank of an existing UPS present in a facility, where it functions as a DC-DC converter to provide
PV based energy support. However, such an operation of RBGTI requires several questions to
be resolved in terms of hardware configuration, islanding behavior, battery management, and
overall system control, which are addressed in this work.
For the islanding behavior in grid-tied mode, a dynamic-phasor based GTI system model
is proposed that captures the system dynamics accurately after unintentional islanding and
allows systematic stability study based on eigenvalue analysis. In the battery-tied mode, a
dynamic model of the PV fed battery charge-controller system is proposed which facilitates the
systematic design of a maximum-power-point tracking (MPPT) controller and a load current
tracking controller for the RBGTI, that achieves the effect of a virtual PV based batterybank in parallel with the physical UPS battery. A supervisory RBGTI control scheme is
proposed that ensures stable system operation during dynamic conditions of load power and
solar insolation changes while reducing discharge burden on the UPS battery. A discrete IGBT
converter hardware platform is developed, where the proposed analytical models, controls and
the RBGTI performance are verified on a 4.5 kW experimental setup
31
Chen, Chan-Yi, i 陳展毅. "Analysis and Design of PI Compensator for a Grid-Tied Single-Phase PV Inverter". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/04731989900265169900.
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碩士中原大學
電機工程研究所
100
The purpose of this thesis is to design and realize a gird-tied single-phase PV inverter and investigate a proportional-plus-integral (PI) compensator for system stability and harmonic elimination. In comparison with P controller, the PI controller can provide good ability for harmonic elimination to achieve lower total harmonic distortion (THD). In this work, a DC source like a DC bus from the boost converter and a reference signal from simulation solar panels after maximum power point tracking (MPPT) are used to regulate the output current to grid-tied utility. The system control including PI compensator is analyzed completely and its efforts are applied in the hardware implementation of a 1.5kW PV inverter to verify the estimated analysis and dynamic response. Finally, the harmonics and current THDs produced due to P and PI compensators are compared and analyzed with each other to investigate their performance on system.
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Yi-NingXie i 謝亦甯. "Analysis of Current-fed Multiloop Control Strategies for the Grid-tied Single Phase Inverter". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/n5u9k5.
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碩士國立成功大學
電機工程學系
106
In recent years, renewable energy resources have been promoting the wide development of distributed generation. Most of distributed generation supplies energy to the residential load by means of inverters tied with AC grid. The output of the converter is easily affected by non-linear loads that produces harmonics in the same power system. The output quality of the current fed inverter can be even worse the grid-tied mode. This study focuses on the multi-loop control strategies with harmonic compensation technique that is applied to the single-phase current-fed inverter. The main object is to improve the characteristic of transient response and reduce the total harmonic distortion of the output current at the point of common coupling. This study adopts the LCL filter at the port of inverter output to realize the multi-loop control strategies. Analyses of small signals for the single loop and multi-loop are conducted and the associated performance of the single-phase grid-tied inverter is validated by the simulation results and experimental results. Furthermore, test of the harmonic compensator has shown its function for improving the power quality.
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Wang, Cheng-Hao, i 王政皓. "Maximum Power Point Tracking for a Grid-Tied Photovoltaic Inverter System Under Partial Shading Conditions". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/hukgvj.
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碩士中原大學
電機工程研究所
105
The photovoltaic panels have plural operational regions for power generation under partial shading conditions, such that the traditional maximum power point tracking(MPPT) methods will lead to local maximum power generation. To obtain the global maximum power generation, this thesis proposes a hybrid method by combining Shuffled Frog Leaping Algorithm(SFLA) and Perturb and Observe(P&O) algorithm. A grid-tied PV power generation system is taken as the application, where a boost converter and a full-bridge inverter are used to transfer the PV power for grid-tied systems. Moreover, the neural network based on fractional-order PI current control is used for the current regulation of the full-bridge inverter. Finally, numerical simulation and experimental results show the expected performance of the global maximum power point tracking under partial shading conditions.
34
MANYATSI, THEMBELANI ZWELITHINI, i 張維里. "Research on Three Phase Multi-Input Single-Stage Grid-Tied Inverter for Photovoltaic Power Generation Systems". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/799uym.
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碩士國立勤益科技大學
電機工程系
107
The main purpose of this thesis is to propose a three phase Multi-input Single-stage Grid-tied inverter (MSG-inverter) which can be used in distributed photovoltaic power generation systems (PVPGS). The proposed inverter is composed of micro dc-dc buck-boost converters (BBCs) and a dc-ac unfolder. Each micro BBC is connected to a single photovoltaic module (PV) in a PVPGS. The micro BBCs are connected to the central dc-ac unfolder through a dc bus. The micro BBCs are operating in discontinuous conduction mode (DCM). The pulsating dc current reduces stress and losses in the dc bus. Each micro BBC is equipped with a simple maximum power point tracker (MPPT) designed specifically to achieve maximum energy transfer. Each micro BBC is equipped with an interleaving power control scheme which is controlled using a signal from a phase lock loop (PLL). The architecture and control scheme of the proposed three phase MSG-inverter achieves a distributed MPPT (DMPPT) control and distributed power control of the PV array in distributed PVPGS. Finally some computer simulations results are presented to verify the performance of the proposed MSG-inverter.
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Bala, Krishna Pagadala. "Modular Cascaded H-Bridge Multilevel Inverter with Distributed MPPT for Grid Connected Application". Thesis, 2017. http://ethesis.nitrkl.ac.in/8930/1/2017_MT_PBKrishna.pdf.
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This work presents a modular cascaded H-bridge multilevel photovoltaic (PV) inverter for three-phase grid-connected applications. The topology of modular cascaded H-Bridge multilevel inverter helps to improve the efficiency and flexibility of PV systems. In this work, a distributed maximum power point tracking control scheme is applied for three-phase multilevel inverter to understand a better utilization of PV modules and maximize the solar energy extraction. Because this distributed MPPT control scheme allows independent control of each dc-link voltage. The mismatches in PV panel should takes place in three-phase gridconnected applications, and the above mentioned mismatches can be introduced unbalanced power supply, create an unbalanced grid current. PV mismatches can be controlled by the following technique i.e., a modulation compensation is introduced. By using nine H-bridge modules a three-phase seven-level cascaded H-bridge inverter is built, each phase has three modules. Simulation results are presented to verify the feasibility of the proposed approach.
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Dash, Prajna Paramita. "A High-Performance Three-Phase Grid-Connected PV System Based On Multilevel Current Source Inverter". Thesis, 2013. http://hdl.handle.net/10012/7356.
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Current Source Inverter (CSI) topology is gaining acceptance as a competitive alternative for grid interface of renewable energy systems due to its unique and advantageous features. Merits of CSI over the more popular Voltage Source Inverter (VSI) topology have been elaborated on by a number of researchers. However, there is a dearth of quality work in modeling and control of CSI topology interfacing renewable energy resources to the grid. To enrich the study focussing on application of CSI for renewable energy interface, this thesis develops a multilevel structure based on CSI for three-phase grid-connected Photovoltaic (PV) application. In the first part of research, a single-stage CSI interfacing to PV array is developed. The CSI-based PV system is equipped with Maximum Power Point Tracker (MPPT), DC-link current controller, and AC-side current controller. To eliminate the nonlinearity introduced by the PV array, a feed-forward control is introduced in the DC-link current controller. The AC-side current controller is responsible for maintaining unity power factor at the Point of Common Coupling (PCC). To verify the performance of the developed CSI-based PV system, a number of simulation studies are carried out in PSCAD/EMTDC environment. To illustrate the performance of the CSI-based PV system during transients on the grid side, simulation studies are carried out for four kinds of faults. Results obtained from fault studies are highly in favor of CSI topology and provide illustrative evidence for short-circuit current protection capability of the CSI. On the other hand, the VSI-based PV system performs poorly when subjected to similar grid transients.
To extend the research on CSI-based PV system further, a multilevel structure based on CSI is developed. The multilevel structure is a parallel combination of $n$ CSI units and capable of producing $2n+1$ levels of current at the terminal of the inverter. Each unit in the multilevel structure has its own MPPT, DC-link current controller. However, on the AC-side a combined current controller is proposed. The design results in a high power rating with reduced number of filters, sensors and controllers. The developed multilevel structure can operate with PV arrays exposed to equal and unequal insolation level. However, when the PV arrays are operating under unequal insolation level, low order harmonics are generated in the sinusoidal current that is injected into the grid. Elimination of these harmonics is performed by implementing a modified control strategy in stationary reference frame that corresponds to the harmonic component that needs to be minimized. The modified control strategy operates in coordination with the existing DC-side and AC-side current controllers, and MPPTs. Therefore, real-time suppression of current harmonics can be ensured. Performance of the multilevel structure is verified by different transient studies.
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Huang, Bo Xiang, i 黃柏翔. "Automatic Self-Matching Controller Design for Grid-Tied PV Inverter to Adapt the Change of Source Impedance and Solar Irradiation". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/90651434451583088036.
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碩士長庚大學
電機工程學系
100
The effect of variation in source impedance and solar irradiation on control performance of PV systems is investigated. A proportional-resonant (PR) controller in the stationary frame in place of a proportional-integral (PI) controller in the synchronous frame was adopted to modulate a single-phase grid-tied inverter for the PV systems. Although the PR controllers have gained some momentum lately due to the advantages such as instantaneous tracking capability as well as low-cost computational resources, the tracking performance may decline in case of the change in source impedance and solar irradiation where conventional PR design rule is void. To adapt the PR controllers over diverse operating conditions without incurring excessive tracking error, an adaptive algorithm, which dictates the quality of the tracking performance, is proposed to search appropriate damping ratio for the PV systems. The control gains of the PR-controller can then be altered in light of the optimal damping ratio through a simple algebraic conversion. The proposed strategy was realized by a fully digital-controlled laboratory prototype which consists of a 1.5kW PV array and a grid-tied single-phase inverter. The experimental results confirm the performance of the proposed strategy.
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Dash, Ashish Ranjan. "Investigation of Cascaded Multilevel Inverter Based SAF with Alternative Configurations Under Ideal and Nonideal Grid Voltage Conditions". Thesis, 2019. http://ethesis.nitrkl.ac.in/10125/1/2019_PhD_ARDash_514EE6022_Investigation.pdf.
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Issue of harmonics is a greater apprehension as it severely affects the power quality of the supply and utility. Increased use of nonlinear loads in medium and high power application causes a shocking intensification of harmonic pollution, which results in several negative consequences. As a result, the performance analysis of power conditioning devices has become very crucial in the design and engineering process. Over the years, active power filter (APF) gains much more attention due to its significant harmonics elimination standard in AC power network and provides a wider perspective to researchers and application engineers dealing with power quality issues. Among the various power conditioning devices, shunt active filter (SAF) gains popularity for significant harmonic elimination during extremely non-linear load conditions. The conventional SAF configurations are based on two-level inverters. The power managing ability of these inverters is low, so it is not an appropriate choice for high power application, hence limited to low power applications. However, Multilevel Inverter (MLI) operates in lesser switching frequency and the harmonic elimination capability is quite high compared to these two-level inverters. So MLIs are preferable to operate as a SAF and extend effective performance in high power applications. Among the different topologies of multilevel inverters, cascaded H-bridge multilevel inverter (CHBMLI) have several advantages but its major drawback is handling of separate DC sources for each module. So with more number of individual DC sources, the control complexity with increasing sensors becomes difficult to handle. However, the above-mentioned problems can be effectively eradicated if CHBMLI operates with a single DC source. In the present work, the drawback of conventional CHBMLI is eradicated by introducing a cascaded MLI adopting cascaded transformers which operates with single DC source. The proposed cascaded MLI is investigated under various PWM techniques to show its effectiveness. The purpose of the research is to introduce an alternative approach to limit harmonics by proposing effective method yet developing the appropriate mathematical models and then validating models with the simulations and experiments. So, the ultimate goal is to investigate the performance of the proposed cascaded MLI based shunt active filter and to mitigate the control problems associated with it under ideal and nonideal source voltage condition. During unbalanced and distorted input condition many control technique fails to generate a significant reference current to achieve proper compensation. Since these control techniques are sensitive to frequency deviation and imbalance, significant harmonic elimination cannot be achieved. So in order to deal with these issues, different harmonic extraction control techniques are compared and alternative control techniques are proposed and its performance is also analysed in the present work. The performance of the proposed SAF is investigated using 𝑖𝑑−𝑖𝑞 control technique and a comparative evaluation is carried out by applying carrier based PWM and SVM technique. A comparison is carried out between the previously addressed 𝑖𝑑−𝑖𝑞 control, improved 𝑝−𝑞 control and PHC control technique under balanced, unbalanced and distorted source voltage condition. Further, a real time empirical mode decomposition (RT-EMD) based control technique and a novel spline EMD based control technique is adopted for effective mitigation of system harmonics under ideal and nonideal supply voltage conditions. The significance of the proposed control technique is evaluated in steady state and transient condition with ideal and nonideal source voltage condition. Finally, the proposed hardware setup is also verified under steady-state, transient and load unbalanced conditions under ideal and nonideal input voltage condition adopting different control technique.
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Sajadian, Sally. "Energy conversion unit with optimized waveform generation". Thesis, 2014. http://hdl.handle.net/1805/6109.
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Indiana University-Purdue University Indianapolis (IUPUI)The substantial increase demand for electrical energy requires high efficient apparatus dealing with energy conversion. Several technologies have been suggested to implement power supplies with higher efficiency, such as multilevel and interleaved converters. This thesis proposes an energy conversion unit with an optimized number of output voltage levels per number of switches nL=nS. The proposed five-level four-switch per phase converter has nL=nS=5/4 which is by far the best relationship among the converters presented in technical literature. A comprehensive literature review on existing five-level converter topologies is done to compare the proposed topology with conventional multilevel converters. The most important characteristics of the proposed configuration are: (i) reduced number of semiconductor devices, while keeping a high number of levels at the output converter side, (ii) only one DC source without any need to balance capacitor voltages, (iii) high efficiency, (iv) there is no dead-time requirement for the converters operation, (v) leg isolation procedure with lower stress for the DC-link capacitor. Single-phase and three-phase version of the proposed converter is presented in this thesis. Details regarding the operation of the configuration and modulation strategy are presented, as well as the comparison between the proposed converter and the conventional ones. Simulated results are presented to validate the theoretical expectations. In addition a fault tolerant converter based on proposed topology for micro-grid systems is presented. A hybrid pulse-width-modulation for the pre-fault operation and transition from the pre-fault to post-fault operation will be discussed. Selected steady-state and transient results are demonstrated to validate the theoretical modeling.