Journal articles: 'Impedance convertor'

1

Fabre, A., and O. Saaid. "Novel translinear impedance convertor and bandpass filter applications." Electronics Letters 29, no. 9 (1993): 746. http://dx.doi.org/10.1049/el:19930500.

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Miguel, J. M. "New positive-impedance convertor suitable for high-frequency application." Electronics Letters 21, no. 9 (1985): 402. http://dx.doi.org/10.1049/el:19850286.

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Liang, Zhiming, Bin Li, Zhaohui Wu, and Yunfeng Hu. "A high input impedance chopper amplifier using negative impedance convertor for implantable EEG recording." IEICE Electronics Express 17, no. 17 (September 10, 2020): 20200238. http://dx.doi.org/10.1587/elex.17.20200238.

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Takagi, S., and N. Fujii. "Novel highly linear MOS integrator using a negative impedance convertor (NIC)." Electronics Letters 30, no. 10 (May 12, 1994): 746–48. http://dx.doi.org/10.1049/el:19940547.

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Watanabe, Tomoki, Noriko Fukuda, and Satoru Hatsukade. "Control of a PWM Convertor for Linear Generator as a Variable Impedance." IEEJ Transactions on Industry Applications 120, no. 2 (2000): 288–96. http://dx.doi.org/10.1541/ieejias.120.288.

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Li, Wenxing, Ning Zhai, Ruilong Chen, and Wenhua Yu. "Non-Foster Impedance Wideband Matching Technique for Electrically Small Active Antenna." International Journal of Antennas and Propagation 2013 (2013): 1–7. http://dx.doi.org/10.1155/2013/531419.

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This paper investigates a non-Foster wideband circuit matching technique for an electrically small antenna (ESA). By introducing a negative impedance convertor into an active network, the active network can obtain an equivalent input gain at input port to improve gain, sensitivity and output ratio of signal to noise. In addition, it also increases the effective height of active antenna. The experimental results have verified the proposed method by using a 100 KHz–30 MHz wideband active receiving monopole antenna.

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Zhang, Song, Guoqing Li, Shuguang Li, and Xintong Liu. "A Method of Demarcating Critical Failure Impedance Boundary of Multi-Infeed HVDC Systems Based on Minimum Extinction Angle." Mathematical Problems in Engineering 2021 (August 31, 2021): 1–14. http://dx.doi.org/10.1155/2021/9923737.

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A method of rapidly demarcating the critical commutation failure (CF) region of a multi-infeed high-voltage direct-current (HVDC) system is proposed. Based on the nodal impedance matrix and nodal voltage interaction factor, for different AC fault conditions—both balanced and unbalanced—a method of calculating the extinction angles of converters in multi-infeed HVDC systems is deduced in detail. First, the extinction angles of convertor stations under single-phase, double-phase, and three-phase ground faults and line-to-line faults occurring at any bus in an AC system are calculated. The minimum extinction angle serves as a CF criterion. If the calculated extinction angle for a certain bus is smaller than the minimum extinction angle, then a fault at that bus will cause CF of the HVDC system and put that bus into a failed bus set. The critical failure impedance boundaries of the topology diagram can therefore be demarcated by examining every bus in the AC system. The validity and accuracy of the proposed index and the method were verified by calculation results based on the three-infeed HVDC system model of the IEEE 39-bus system. Finally, the critical failure impedance boundary was demarcated in the IEEE 118-bus system to demonstrate the application in a wider range of systems.

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Lahiri, A. "DO-CCII Based Generalised Impedance Convertor Simulates Floating Inductance, Capacitance Multiplier and Fdnr." Australian Journal of Electrical and Electronics Engineering 7, no. 1 (January 2010): 15–20. http://dx.doi.org/10.1080/1448837x.2010.11464253.

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Ding, Yuan, and Vincent Fusco. "Loading artificial magnetic conductor and artificial magnetic conductor absorber with negative impedance convertor elements." Microwave and Optical Technology Letters 54, no. 9 (June 18, 2012): 2111–14. http://dx.doi.org/10.1002/mop.27019.

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Hu, Pengfei, Li Shen, Feng Han, Fei Yang, Maojiang Song, Li Zhang, and Liping Liu. "Development of the data acquisition system for terahertz spectrometer." Transactions of the Institute of Measurement and Control 40, no. 3 (April 6, 2017): 805–11. http://dx.doi.org/10.1177/0142331217690475.

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In most Terahertz time-domain spectrometer (THz-TDS) experiments, the lock-in amplifier works with trans-impedance pre-amplifier to amplitude the terahertz pulse accepted from detector. This paper discusses the development of data acquisition system for the transmission THz-TDS. In this system, the cross-correlation software algorithm in SR830 lock-in amplifier from Stanford Research Systems, that is usually used in THz-TDS, has been replaced by parallel hardware algorithm of Field Programmable Gate Array (FPGA) chip with the parallel processing ability. This chip has a faster processing speed and higher accuracy than others. A 24 bit Delta-Sigma Analog Digital (AD) was used in place of the 16 bit successive approximation ADC of SR830. The new AD convertor can reduce the complexity of trans-impedance pre-amplifier circuit and replace the SR555 current amplifiers that designed to work with SRS lock-in amplifiers. Besides trans-impedance pre-amplifier circuit, all function circuits, such as low-pass digital filter, phase-locked loop, Direct Digital Synthesis (DDS) reference source and the core algorithms, are integrated in a FPGA chip, which make the new designed lock-in amplifier with a small volume reduce a dozen times SR830 size.

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Pidaparthy, Syam Kumar, and Byungcho Choi. "Control Design and Loop Gain Analysis of DC-to-DC Converters Intended for General Load Subsystems." Mathematical Problems in Engineering 2015 (2015): 1–10. http://dx.doi.org/10.1155/2015/426315.

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DC-to-DC converters are usually intended for general applications where the load impedance characteristics are unknown or undefined. This paper establishes the control design procedures for DC-to-DC converters in the absence of any prior knowledge on their load impedance. The proposed control design can be universally adapted to all the DC-to-DC converters regardless of the impedance characteristics of their actual load. This paper also presents the loop gain analysis of the converter combined with an actual load whose impedance characteristics are only available afterward. A graphical analysis method is proposed, which enables us to predict the loop gain of the converter in the presence of an arbitrary load impedance. The validity of the analysis method is demonstrated using a current-mode controlled buck converter coupled with an inductive load, capacitive load, and converter load. Theoretical predictions are verified with both computer simulations and experimental measurements.

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Quester, Matthias, Fisnik Loku, Otmane El Azzati, Leonel Noris, Yongtao Yang, and Albert Moser. "Investigating the Converter-Driven Stability of an Offshore HVDC System." Energies 14, no. 8 (April 20, 2021): 2341. http://dx.doi.org/10.3390/en14082341.

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Offshore wind farms are increasingly built in the North Sea and the number of HVDC systems transmitting the wind power to shore increases as well. To connect offshore wind farms to adjacent AC transmission systems, onshore and offshore modular multilevel converters transform the transmitted power from AC to DC and vice versa. Additionally, modern wind farms mainly use wind turbines connected to the offshore point of common coupling via voltage source converters. However, converters and their control systems can cause unwanted interactions, referred to as converter-driven stability problems. The resulting instabilities can be predicted by applying an impedance-based analysis in the frequency domain. Considering that the converter models and system data are often confidential and cannot be exchanged in real systems, this paper proposes an enhanced impedance measurement method suitable for black-box applications to investigate the interactions. A frequency response analysis identifies coupling currents depending on the control system. The currents are subsequently added to the impedance models to achieve higher accuracy. The proposed method is applied to assess an offshore HVDC system’s converter-driven stability, using impedance measurements of laboratory converters and a wind turbine converter controller replica. The results show that the onshore modular multilevel converter interacts with AC grids of moderate short-circuit ratios. However, no interactions are identified between the offshore converter and the connected wind farm.

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Luhtala, Roni, Tuomas Messo, Tomi Roinila, Henrik Alenius, Erik de Jong, Andrew Burstein, and Alejandra Fabian. "Identification of Three-Phase Grid Impedance in the Presence of Parallel Converters." Energies 12, no. 14 (July 12, 2019): 2674. http://dx.doi.org/10.3390/en12142674.

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Grid impedance is an important parameter which affects the control performance of grid-connected power converters. Several methods already exist for optimizing the converter control system based on knowledge of grid impedance value. Grid impedance may change rapidly due to fault or disconnection of a transmission line. Therefore, online grid identification methods have been recently proposed to have up-to-date information about the grid impedance value. This is usually done by perturbing the converter output current and measuring the response in output voltage. However, any parallel converters connected to the same interface point will cause errors, since the measured current differs from the current that is flowing through the grid interface point. This paper points out challenges and errors in grid impedance identification, caused by parallel converters and their internal control functions, such as grid-voltage support. Experimental grid-impedance measurements are shown from the power hardware-in-the-loop setup developed at DNV-GL Flexible Power Grid Lab.

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Li, Yuye, Kaipei Liu, Xiaobing Liao, Shu Zhu, and Qing Huai. "A Virtual Impedance Control Strategy for Improving the Stability and Dynamic Performance of VSC–HVDC Operation in Bidirectional Power Flow Mode." Applied Sciences 9, no. 15 (August 5, 2019): 3184. http://dx.doi.org/10.3390/app9153184.

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It is a common practice that one converter controls DC voltage and the other controls power in two-terminal voltage source converter (VSC)–based high voltage DC (HVDC) systems for AC gird interconnection. The maximum transmission power from a DC-voltage-controlled converter to a power-controlled converter is less than that of the opposite transmission direction. In order to increase the transmission power from a DC-voltage-controlled converter to a power-controlled converter, an improved virtual impedance control strategy is proposed in this paper. Based on the proposed control strategy, the DC impedance model of the VSC–HVDC system is built, including the output impedance of two converters and DC cable impedance. The stability of the system with an improved virtual impedance control is analyzed in Nyquist stability criterion. The proposed control strategy can improve the transmission capacity of the system by changing the DC output impedance of the DC voltage-controlled converter. The effectiveness of the proposed control strategy is verified by simulation. The simulation results show that the proposed control strategy has better dynamic performance than traditional control strategies.

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Mucha, A., M. Schienle, and D. Schmitt-Landsiedel. "A CMOS integrated impedance-to-frequency converter for sensing cellular adhesion." Advances in Radio Science 9 (August 1, 2011): 281–87. http://dx.doi.org/10.5194/ars-9-281-2011.

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Abstract. Sensing cellular adhesion via impedance measurements provides a versatile and easily accessible means for monitoring in-vitro cell cultures. Previous works used external electronics connected via cables to microelectrodes to achieve this goal, thus incurring parasitic impedance, electromagnetic interference, and bulky measurement setups. In this work we present a CMOS impedance-to-frequency converter integrated with biocompatible planar surface electrodes to make a compact and robust sensor chip for in-vitro cell monitoring. The system features an 8×8 array of individually addressable electrodes connected to four impedance-to-frequency converter circuits with externally adjustable biasing and square wave output. We present first measurement results obtained with the integrated electronics that demonstrate the successful operation of the system and show good agreement with models of the electrode and cell impedances.

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Herbst, Gernot. "A Building-Block Approach to State-Space Modeling of DC-DC Converter Systems." J 2, no. 3 (July 8, 2019): 247–67. http://dx.doi.org/10.3390/j2030018.

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Small-signal models of DC-DC converters are often based on a state-space averaging approach, from which both control-oriented and other frequency-domain characteristics, such as input or output impedance, can be derived. Updating these models when extending the converter by filters or non-trivial loads, or adding control loops, can become a tedious task, however. To simplify this potentially error-prone process, a modular modeling approach is being proposed in this article. It consists of small state-space models for certain building blocks of a converter system on the one hand, and standardized operations for connecting these subsystem models to an overall converter system model on the other hand. The resulting state-space system model builds upon a two-port converter description and allows the extraction of control-oriented and impedance characteristics at any modeling stage, be it open loop or closed loop, single converter or series connections of converters. The ease of creating more complex models enabled by the proposed approach is also demonstrated with examples comprising multiple control loops or cascaded converters.

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Gadalla, Brwene Salah, Erik Schaltz, Yam Siwakoti, and Frede Blaabjerg. "Analysis of loss distribution of Conventional Boost, Z-source and Y-source Converters for wide power and voltage range." Transactions on Environment and Electrical Engineering 2, no. 1 (January 1, 2017): 1. http://dx.doi.org/10.22149/teee.v2i1.68.

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Boost converters are needed in many applications which require the output voltage to be higher than the input voltage. Recently, boost type converters have been applied for industrial applications, and hence it has become an interesting topic of research. Many researchers proposed different impedance source converters with their unique advantages as having a high voltage gain in a small range of duty cycle ratio. However, the thermal behaviour of the semiconductor devices and passive elements in the impedance source converter is an important issue from a reliability point of view and it has not been investigated yet. Therefore, this paper presents a comparison between the conventional boost, the Z-source, and the Y-source converters based on a thermal evaluation of the semiconductors. In addition, the three topologies are also compared with respect to their efficiency. In this study the results show that the boost converter has higher efficiency than the Zsource and Y-source converter for these specific voltage gain of 2 and 4. The operational principle, mathematical derivations, simulation results and final comparisons are presented in this paper.

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Zhang, Zhuang, Liu, Wang, and Guo. "A Novel Autonomous Current-Sharing Control Strategy for Multiple Paralleled DC–DC Converters in Islanded DC Microgrid." Energies 12, no. 20 (October 17, 2019): 3951. http://dx.doi.org/10.3390/en12203951.

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Due to the existence of line impedances and low-bandwidth communication, the traditional peer-to-peer control method based on droop control has difficult meeting the requirements of current sharing and voltage stability in islanded DC microgrids at the same time. In this paper, a novel current-sharing control strategy based on injected small ac voltage with low frequency and low amplitude is proposed for multiple paralleled DC–DC converters. The small ac voltage is superimposed onto the output voltage of each converter. Then, the reactive circulating power is generated and used to regulate the output DC voltage of each converter. Under the droop characteristic between the injected frequency and output DC current, a feedback mechanism is generated to realize the accurate current sharing. On this basis, a reactive power-voltage limiter link and virtual negative impedance are added. Under the interaction of the two links, the bus voltage drop caused by line impedances can be almost completely eliminated. This method does not need any communication or to change the hardware structure. The controller design process is presented in detail along with a system stability analysis. Finally, the feasibility and effectiveness of the proposed control strategy are validated by the results obtained from simulations and experiments.

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Ado, Muhammad, Awang Jusoh, and Tole Sutikno. "Asymmetric quasi impedance source buck-boost converter." International Journal of Electrical and Computer Engineering (IJECE) 10, no. 2 (April 1, 2020): 2128. http://dx.doi.org/10.11591/ijece.v10i2.pp2128-2138.

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An impedance source buck-boost converter (BBC) prototype for renewable energy (RE) application in the transportation industry is proposed. Its functions include stabilizing the variable output voltage of the RE sources such as fuel cells and photovoltaic cells. The converter utilized a topology of DC-DC quasi-impedance source converters (q-ZSCs) to achieve the gain curve of the BBC. With BBC gain curve, the converter earned advantages over the two other classes of non-isolated DC-DC q-ZSCs. These advantages include ecient buck-boost capability at the ecient duty ratio range of 0:35-0:65 and continuous and non-zero gain at the ecient duty ratio range. The converter's q-ZSC topology implies using two capacitors and two inductors. These two capacitors and inductors formed two separate LC filters that provides second order filtering compared to the first order filtering in BBC. Its other advantages over the traditional BBC include elim-ination of dead and overlap-time, simple contol and permitting higher switching frequency operation. The converter is capable of utilizing high switching frequency and asymmetric components to achieve BBC gain by using smaller components to reduce cost, weight and size. Its simulation response and that of a correspond-ing BBC for some given specifications were compared, presented and analyzed. An experimental scaled-down prototype was also developed to confirm its opera-tion. Analysis of the converters responses comfirmed the prototype's second order filtering as against the first order filtering in traditional BBC.

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Salehi, Navid, Herminio Martínez-García, and Guillermo Velasco-Quesada. "Modified Cascaded Z-Source High Step-Up Boost Converter." Electronics 9, no. 11 (November 17, 2020): 1932. http://dx.doi.org/10.3390/electronics9111932.

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To improve the voltage gain of step-up converters, the cascaded technique is considered as a possible solution in this paper. By considering the concept of cascading two Z-source networks in a conventional boost converter, the proposed topology takes the advantages of both impedance source and cascaded converters. By applying some modifications, the proposed converter provides high voltage gain while the voltage stress of the switch and diodes is still low. Moreover, the low input current ripple of the converter makes it absolutely appropriate for photovoltaic applications in expanding the lifetime of PV panels. After analyzing the operation principles of the proposed converter, we present the simulation and experimental results of a 100 W prototype to verify the proposed converter performance.

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Chen, Xunjun, and Zhigang Liu. "Impedance Modeling and Stability Analysis of the Converters in a Double-Fed Induction Generator (DFIG)-Based System." Energies 12, no. 13 (June 28, 2019): 2500. http://dx.doi.org/10.3390/en12132500.

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Harmonic stability of double-fed induction generators (DFIGs) now has become a significant topic because of its harmful impact on power quality issues of the system. Since the double pulse width modulation (PWM) converter is one of the main harmonic sources in DFIGs, it may cause harmonic instability with increasing harmonic contents. Thus, the modeling and stability analyses of PWM converters in DFIGs are essential steps to assess the harmonic stability of DFIGs. Aiming at dual PWM converters, which include the grid side converter (GSC) and the rotor side converter (RSC), this paper divides converters into two parts: circuit modules and control modules. Closed-loop input impedance models of each module are then derived by means of transfer functions. Hence, the stability of the system can be readily predicted through Nyquist diagrams. The contributions of parameters to the system’s harmonic stability are also identified. Finally, time-domain simulations are conducted in a real-time digital simulation (RTDS) system. Simulation results confirm that the established impedance model can effectively reveal the stability of the DFIG-based system and can give critical conditions for the occurrence of harmonic instability.

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Santos, José, and Pedro Ramos. "DSPIC-Based Impedance Measuring Instrument." Metrology and Measurement Systems 18, no. 2 (January 1, 2011): 185–98. http://dx.doi.org/10.2478/v10178-011-0002-0.

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DSPIC-Based Impedance Measuring Instrument An implemented impedance measuring instrument is described in this paper. The device uses a dsPIC (Digital Signal Peripheral Interface Controller) as a processing unit, and a DDS (Direct Digital Synthesizer) to stimulate the measurement circuit composed by the reference impedance and the unknown impedance. The voltages across the impedances are amplified by programmable gain instrumentation amplifiers and then digitized by analog to digital converters. The impedance is measured by applying a seven-parameter sine-fitting algorithm to estimate the sine signal parameters. The dsPIC communicates through RS-232 or USB with a computer, where the measurement results can be analyzed. The device also has an LCD to display the measurement results.

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Yao, Qi, Dylan-Dah-Chuan Lu, and Gang Lei. "Accurate Online Battery Impedance Measurement Method with Low Output Voltage Ripples on Power Converters." Energies 14, no. 4 (February 18, 2021): 1064. http://dx.doi.org/10.3390/en14041064.

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The conventional online battery impedance measurement method works by perturbing the duty cycle of the DC-DC power converter and measuring the response of the battery voltage and current. This periodical duty cycle perturbation will continuously generate large voltage ripples at the output of power converters. These large ripples will not easily be removed due to the high amplitude and wide frequency range and would be a challenge to meet tight output regulation. To solve this problem, this paper presents a new online battery impedance measurement technique by inserting a small switched resistor circuit (SRC) into the converter. The first contribution of this work is that the perturbation source is moved from the main switch to the input-side of the converter, so the ripples are reduced. The analysis and experimental results of the proposed method show a reduction of 16-times compared with the conventional method. The second contribution tackles the possible change of the battery state of charge (SOC) during the online battery measurement process, which will inevitably influence the impedance measurement accuracy. In this proposed method, battery impedance at multiple frequencies can be measured simultaneously using only one perturbation to accelerate measurement speed and minimize possible SOC change. The experimental impedance results coincide with a high-accuracy laboratory battery impedance analyzer.

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Xie, Guang Jun, Hai Bin Fang, and Hui Fang Xu. "Analysis of Multi-Converter System’s Stability Using the Active Damping Method." Applied Mechanics and Materials 58-60 (June 2011): 950–55. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.950.

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In Multi-converter power electronic systems, load converters exhibit constant power load (CPL) behavior for the feeder converters and tend to destabilize the system. In this paper, Buck DC-DC converters are taken as an example, and the implementation of active-damping techniques has been shown to analyze the stability of multi-converter power electronic systems. Moreover, active damping is generally implemented by a feedback loop, which produces the effect of a virtual resistor and damps the oscillations, the proposed active-damping method can overcome the negative impedance instability problem caused by the CPLs. The effectiveness of the proposed approach has been verified by Matlab/Simulink simulations.

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Janke, W., M. Bączek, and M. Walczak. "Output characteristics of step-down (Buck) power converter." Bulletin of the Polish Academy of Sciences: Technical Sciences 60, no. 4 (December 1, 2012): 751–55. http://dx.doi.org/10.2478/v10175-012-0086-6.

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Abstract The output characteristics of switched-mode dc-dc buck power converter are discussed. The shape of output characteristics is especially important for converters used for supplying modern processors. An output impedance is usually used for description of output characteristics. Many efforts are described in the literature to obtain the satisfastory features of closed-loop output impedance. Another approach, presented in the paper, is based on the concept of the output voltage response corresponding to the load conductance change, and is expressed by hr transmittance. Simulations of output characteristics of the buck converter in frequency and in time-domain have been performed for the ideal case as well as for a more realistic situation, with the parasitic resistances of converter elements included. The measurement results differ substantially from characteristics calculated for an ideal converter and are in good consistency with simulations including parasitics.

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Yu, Zhi Yong, Ming Lu, Zhen Nan Wang, and Yi Gong Zhang. "A Droop Control Strategy with Impedance Compensation for Low Voltage Microgrid." Applied Mechanics and Materials 441 (December 2013): 245–48. http://dx.doi.org/10.4028/www.scientific.net/amm.441.245.

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With conventional droop control, parallel operation of distributed generations (DG) in microgrid would lead to unbalanced power sharing. In this paper, inherent limitation of conventional droop control is analyzed. Analysis results show that different converter output impedance and line impedance make the power sharing unbalanced. In order to weaken or eliminate impedance difference from point of common coupling (PCC) to DGs, virtual impedance is introduced. By the introduction of designed virtual impedance, a novel droop control strategy with impedance compensation is proposed in this paper. Simulation results are presented from a two converters parallel-connected microgrid, showing the effectiveness of the droop control with impedance compensation. Simulation results show that DGs with proposed approach can allocate the power equally, and work stably in grid-connected mode, island mode and progress of reconnection to grid.

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Pratomo, L. Heru, F. Danang Wijaya, and Eka Firmansyah. "Impedance Matching Method in Two-Stage Converters for Single Phase PV-Grid System." International Journal of Electrical and Computer Engineering (IJECE) 5, no. 4 (August 1, 2015): 626. http://dx.doi.org/10.11591/ijece.v5i4.pp626-635.

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This paper presents the study on the impedance matching method in two-stage converters for single phase PV-grid system. The use of PV systems was to obtain the electrical power from the sunlight energy. The system consisted of a Buck-Boost DC-DC converter and a five-level inverter. A Buck-Boost DC-DC converter was used as a means of impedance matching to obtain the maximum power that, in this case, through a method by using the incremental conductance current control algorithm. Meanwhile a five-level inverter was used as an interface to the utilities. By using this technique, the system came to be simple. The impedance of the power grid, a Buck-Boost DC-DC converter, and a five-level inverter were seen by PV mostly in the area of R<sub>MPP</sub>, enabling the maximum power produced by the PV to be delivered to the grid. To demonstrate the effectiveness of the design, the analysis and simulation results, furthermore, were provided

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Husev, Shults, Vinnikov, Roncero-Clemente, Romero-Cadaval, and Chub. "Comprehensive Comparative Analysis of Impedance-Source Networks for DC and AC Application." Electronics 8, no. 4 (April 5, 2019): 405. http://dx.doi.org/10.3390/electronics8040405.

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This paper presents a comprehensive analytical comparison of the impedance-source-based dc-dc and dc-ac converters in terms of the passive component count and size, semiconductor stress, and range of input voltage variation. The conventional solution with a boost converter was considered as a reference value. The main criterion of the comprehensive comparison was the energy stored in the passive elements, which was considered both under a constant and predefined high frequency current ripple in the inductors and the voltage ripple across the capacitors. Main impedance-source converters with or without a transformer and with or without inductor coupling were analyzed. Dc-dc and dc-ac applications were considered. Selective simulation results along with experimental verification are shown. The conclusions provide a selection guide of impedance-source networks for different applications taking into account its advantages and disadvantages.

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Casadei, Filippo, Benjamin S. Beck, Kenneth A. Cunefare, and Massimo Ruzzene. "Vibration control of plates through hybrid configurations of periodic piezoelectric shunts." Journal of Intelligent Material Systems and Structures 23, no. 10 (May 6, 2012): 1169–77. http://dx.doi.org/10.1177/1045389x12443014.

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Periodic arrays of hybrid-shunted piezoelectric actuators are used to suppress vibrations of an aluminum plate over broad frequency bands. Commonly, piezoelectric-shunted networks are used for individual mode control, through tuned, resonant resistive/inductive circuits, and for broadband vibration attenuation, through negative impedance converters. Periodically placed resonant shunts allow for broadband reduction resulting from the attenuation of propagating waves in frequency bands which are defined by the spatial periodicity of the array and by the shunting parameters considered on the circuit. Such attenuation typically occurs at medium–high frequencies, while negative impedance converter networks are effective in reducing the vibration amplitudes of the lower modes of the structure. In this article, the combination of periodic resonant shunts and negative impedance converter networks on the same aluminum panel is studied to verify the possibility of combining the advantages of the two concepts. Both numerical and experimental investigations demonstrate that broadband attenuation is achieved in the mid–high frequency regimes due to the presence of resistive/inductive networks, while the combination with negative impedance converter circuits is responsible for amplitude reduction of the full frequency spectrum. Numerical simulations and frequency response measurements on a plate demonstrate that an attenuation region of about 1000 Hz is achieved with a maximum 8 dB vibration reduction.

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Zhang, Shuaitao, Baihua Zhang, Qiang Lin, Eiji Takegami, Masahito Shoyama, and Gamal M. Dousoky. "Modeling and Optimization of Impedance Balancing Technique for Common Mode Noise Attenuation in DC-DC Boost Converters." Electronics 9, no. 3 (March 14, 2020): 480. http://dx.doi.org/10.3390/electronics9030480.

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As an effective means of suppressing electromagnetic interference (EMI) noise, the impedance balancing technique has been adopted in the literature. By suppressing the noise source, this technique can theoretically reduce the noise to zero. Nevertheless, its effect is limited in practice and also suffers from noise spikes. Therefore, this paper introduces an accurate frequency modeling method to investigate the attenuation degree of noise source and redesign the impedance selection accordingly in order to improve the noise reduction capability. Based on a conventional boost converter, the common mode (CM) noise model was built by identifying the noise source and propagation paths at first. Then the noise source model was extracted through capturing the switching voltage waveform in time domain and then calculating its Fourier series in frequency domain. After that, the conventional boost converter was modified with the known impedance balancing techniques. This balanced circuit was analyzed with the introduced modeling method, and the equivalent noise source was precisely estimated by combining the noise spectra and impedance information. Furthermore, two optimized schemes with redesigned impedances were proposed to deal with the resonance problem. A hardware circuit was designed and built to experimentally validate the proposed concepts. The experimental results demonstrate the feasibility and effectiveness of the proposed schemes.

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Garriga-Castillo, Juan A., Hugo Valderrama-Blavi, José A. Barrado-Rodrigo, and Àngel Cid-Pastor. "Analysis of Sliding-Mode Controlled Impedance Matching Circuits for Inductive Harvesting Devices." Energies 12, no. 20 (October 12, 2019): 3858. http://dx.doi.org/10.3390/en12203858.

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A sea-wave energy harvesting, articulated device is presented in this work. This hand-made, wooden device is made combining the coil windings of an array of three single transducers. Taking advantage of the sea waves sway, a linear oscillating motion is produced in each transducer generating an electric pulse. Magnetic fundamentals are used to deduce the electrical model of a single transducer, a solenoid-magnet device, and after the model of the whole harvesting array. The energy obtained is stored in a battery and is used to supply a stand-alone system pay-load, for instance a telecom relay or weather station. To maximize the harvested energy, an impedance matching circuit between the generator array and the system battery is required. Two dc-to-dc converters, a buck-boost hybrid cell and a Sepic converter are proposed as impedance adaptors. To achieve this purpose, sliding mode control laws are introduced to impose a loss free resistor behavior to the converters. Although some converters operating at discontinuous conduction mode, like the buck-boost converter, can exhibit also this loss free resistor behavior, they usually require a small input voltage variation range. By means of sliding mode control the loss free resistor behavior can be assured for any range of input voltage variation. After the theoretical analysis, several simulation and experimental results to compare both converters performance are given.

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Dunets, Roman, Bogdan Dzundza, and Oksana Kostyuk. "SPECIALIZED SOFTWARE AND HARDWARE FOR IMPEDANCE SPECTROSCOPY OF THERMOELECTRIC ENERGY CONVERTERS." Measuring Equipment and Metrology 81, no. 4 (2020): 18–24. http://dx.doi.org/10.23939/istcmtm2020.04.018.

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Messo, Tuomas, Roni Luhtala, Tomi Roinila, Erik de Jong, Rick Scharrenberg, Tommaso Caldognetto, Paolo Mattavelli, Yin Sun, and Alejandra Fabian. "Using High-Bandwidth Voltage Amplifier to Emulate Grid-Following Inverter for AC Microgrid Dynamics Studies." Energies 12, no. 3 (January 25, 2019): 379. http://dx.doi.org/10.3390/en12030379.

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AC microgrid is an attractive way to energize local loads due to remotely located renewable generation. The AC microgrid can conceptually comprise several grid-forming and grid-following power converters, renewable energy sources, energy storage and local loads. To study the microgrid dynamics, power-hardware-in-the-loop (PHIL)-based test setups are commonly used since they provide high flexibility and enable testing the performance of real converters. In a standard PHIL setup, different components of the AC microgrid exist as real commercial devices or electrical emulators or, alternatively, can be simulated using real-time simulators. For accurate, reliable and repeatable results, the PHIL-setup should be able to capture the dynamics of the microgrid loads and sources as accurately as possible. Several studies have shown how electrical machines, dynamic RLC loads, battery storages and photovoltaic and wind generators can be emulated in a PHIL setup. However, there are no studies discussing how a three-phase grid-following power converter with its internal control functions should be emulated, regardless of the fact that grid-following converters (e.g., photovoltaic and battery storage inverters) are the basic building blocks of AC microgrids. One could naturally use a real converter to represent such dynamic load. However, practical implementation of a real three-phase converter is much more challenging and requires special knowledge. To simplify the practical implementation of microgrid PHIL-studies, this paper demonstrates the use of a commercial high-bandwidth voltage amplifier as a dynamic three-phase power converter emulator. The dynamic performance of the PHIL setup is evaluated by identifying the small-signal impedance of the emulator with various control parameters and by time-domain step tests. The emulator is shown to yield the same impedance behavior as real three-phase converters. Thus, dynamic phenomena such as harmonic resonance in the AC microgrid can be studied in the presence of grid-following converters.

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Huang, Chien-Chun, Sheng-Li Yao, and Huang-Jen Chiu. "Stability Analysis and Optimal Design for Virtual Impedance of 48 V Server Power System for Data Center Applications." Energies 13, no. 20 (October 10, 2020): 5253. http://dx.doi.org/10.3390/en13205253.

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In the past literature on virtual impedance to series systems, most of the discussion focused on stability without in-depth research on the system design of the series converter and the overall output impedance. Accordingly, this study takes an open-loop resonant LLC converter series-connected closed-loop Buck converter as an example. First, the conditions required for the direct connection of the small-signal model in the series, the effect of feedback compensation on the input impedance of the load stage, the operating frequency, and passive components of the two-stage converter are discussed in detail―the relationship between the matching and the output impedance. Afterwards, a mathematical model is used to discuss the effect of adding parallel virtual impedance on the output impedance of the overall series converter and then derive an optimized virtual impedance design. Finally, an experimental platform of 48 V to 12 V and maximum wattage of 96 W are implemented. The output impedance of the series converter is measured with an impedance analyzer to verify the theoretical analysis proposed in this paper.

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Dillersberger, Harald, Bernd Deutschmann, and Douglas Tham. "A Bipolar ±13 mV Self-Starting and 85% Peak Efficiency DC/DC Converter for Thermoelectric Energy Harvesting." Energies 13, no. 20 (October 20, 2020): 5501. http://dx.doi.org/10.3390/en13205501.

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This paper presents a novel converter for boosting the low-voltage output of thermoelectric energy harvesters to power standard electronic circuits. The converter can start up from a fully depleted state of the system off a bipolar ±13 mV input and can boost it to output voltages of up to 5 V. The converter comprises two transformers, one for each polarity that are multiplexed between an oscillator (used during startup) and a flyback converter (used during normal operation). To eliminate leakage currents in the input stage, the unused converter is completely turned off at startup and both converters are automatically shut off if the input power is found to be too low. Measurement results of the converter designed in a 180 nm CMOS process demonstrate a peak end-to-end conversion efficiency of 85% and nearly perfect impedance matching over the full input voltage range. This is the first time that a converter for ultra-low bipolar input voltages achieves the same performance as a unipolar converter.

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de Bessa, Isaías V., Renan L. P. de Medeiros, Iury Bessa, Florindo A. C. Ayres Junior, Alessandra R. de Menezes, Gustavo M. Torres, and João Edgar Chaves Filho. "Comparative Study of Control Strategies for Stabilization and Performance Improvement of DC Microgrids with a CPL Connected." Energies 13, no. 10 (May 25, 2020): 2663. http://dx.doi.org/10.3390/en13102663.

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The DC microgrid system is composed by converters that operate like feeders and loads. Among these loads, we highlight the constant power loads (CPLs) that may cause instability in the microgrid, observed in the form of undesired oscillations due to its negative impedance behavior. Therefore, this work proposes to use performance indices and stability margins to evaluate state and output feedback control strategies for stabilization of DC microgrids. In particular, it is proposed to evaluate the stability margin of the proposed methodologies by means of the impedance relations in the microgrid based on the Middlebrook criterion. Our simulations and tests showed the relation between the performance and stability degradation and the microgrid impedances variation.

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Alenius, Henrik, and Tomi Roinila. "Impedance-Based Stability Analysis of Paralleled Grid-Connected Rectifiers: Experimental Case Study in a Data Center." Energies 13, no. 8 (April 24, 2020): 2109. http://dx.doi.org/10.3390/en13082109.

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Grid-connected systems often consist of several feedback-controlled power-electronics converters that are connected in parallel. Consequently, a number of stability issues arise due to interactions among multiple converter subsystems. Recent studies have presented impedance-based methods to assess the stability of such large systems. However, only few real-life experiences have been previously presented, and practical implementations of impedance-based analysis are rare for large-scale systems that consist of multiple parallel-connected devices. This work presents a case study in which an unstable high-frequency operation, caused by multiple paralleled grid-connected rectifiers, of a 250 kW data center in southern Finland is reported and studied. In addition, the work presents an experimental approach for characterizing and assessing the system stability by using impedance measurements and an aggregated impedance-based analysis. Recently proposed wideband-identification techniques based on binary injection and Fourier methods are applied to obtain the experimental impedance measurements from the input terminals of a single data center rectifier unit. This work provides a practical approach to design and implement the impedance-based stability analysis for a system consisting of multiple paralleled grid-connected converters. It is shown that the applied methods effectively predict the overall system stability and the resonant modes of the system, even with very limited information on the system. The applied methods are versatile, and can be utilized in various grid-connected applications, for example, in adaptive control, system monitoring, and stability analysis.

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Brennan, R. L., T. R. Viswanathan, and J. V. Hanson. "The CMOS negative impedance converter." IEEE Journal of Solid-State Circuits 23, no. 5 (1988): 1272–75. http://dx.doi.org/10.1109/4.5957.

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Varga, L. D., and N. A. Losic. "Synthesis of zero-impedance converter." IEEE Transactions on Power Electronics 7, no. 1 (January 1992): 152–70. http://dx.doi.org/10.1109/63.124588.

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FABRE, A., P. SIARRY, and M. LAMECHE. "Current-controlled translinear impedance converter." International Journal of Electronics 70, no. 4 (April 1991): 795–801. http://dx.doi.org/10.1080/00207219108921328.

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Martinović, Ivan. "Representation of the negative resistance realized with negative impedance converter." Tehnika 74, no. 4 (2019): 549–55. http://dx.doi.org/10.5937/tehnika1904549m.

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Wang, Mian, Fen Tang, Xuezhi Wu, Jingkai Niu, Yajing Zhang, and Jiuhe Wang. "A Nonlinear Control Strategy for DC-DC Converter with Unknown Constant Power Load Using Damping and Interconnection Injecting." Energies 14, no. 11 (May 24, 2021): 3031. http://dx.doi.org/10.3390/en14113031.

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DC-DC converters with constant power loads are mostly used in DC microgrids. Negative impedance and large disturbances of constant power loads may lead to the instability of DC-DC converters. To address this issue, a nonlinear control strategy consisting of an improved passivity-based controller and nonlinear power observer is proposed in this paper. First, an improved passivity-based controller is designed based on the port-controlled Hamiltonian with dissipation model. By proper damping and interconnection injecting, the fast dynamic response of output voltage and stability of the DC-DC converter is achieved. Second, the constant power load is observed by a nonlinear power observer, which is adopted to estimate the power variation of the constant power load within a small settling time and improve the adaptability of the DC-DC converter under power disturbance. Finally, the simulation and experimental results are presented, which illustrate the proposed control strategy not only ensures the stability of the DC-DC converter under large disturbances, but also can track the desired operating point with low voltage overshoot in no more than 10 milliseconds.

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Chabowski, Konrad, Tomasz Piasecki, Andrzej Dzierka, and Karol Nitsch. "Simple Wide Frequency Range Impedance Meter Based on AD5933 Integrated Circuit." Metrology and Measurement Systems 22, no. 1 (March 1, 2015): 13–24. http://dx.doi.org/10.1515/mms-2015-0006.

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Abstract As it contains elements of complete digital impedance meter, the AD5933 integrated circuit is an interesting solution for impedance measurements. However, its use for measurements in a wide range of impedances and frequencies requires an additional digital and analogue circuitry. This paper presents the design and performance of a simple impedance meter based on the AD5933 IC. Apart from the AD5933 IC it consists of a clock generator with a programmable prescaler, a novel DC offset canceller for the excitation signal based on peak detectors and a current to voltage converter with switchable conversion ratios. The authors proposed a simple method for choosing the measurement frequency to minimalize errors resulting from the spectral leakage and distortion caused by a lack of an anti-aliasing filter in the DDS generator. Additionally, a novel method for the AD5933 IC calibration was proposed. It consists in a mathematical compensation of the systematic error occurring in the argument of the value returned from the AD5933 IC as a result. The performance of the whole system is demonstrated in an exemplary measurement.

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Saad, Muhammad, Husan Ali, Huamei Liu, Shahbaz Khan, Haider Zaman, Bakht Khan, Du Kai, and Ju Yongfeng. "A dq-Domain Impedance Measurement Methodology for Three-Phase Converters in Distributed Energy Systems." Energies 11, no. 10 (October 12, 2018): 2732. http://dx.doi.org/10.3390/en11102732.

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A distributed energy system (DES) using controlled power electronics converters delivers power to loads, via conventional, as well as a number of renewable, energy sources. However, stability concerns retard the integration of power electronics converters into an existing DES. Therefore, due to the high penetration of power converters, the overall network analysis of DES is becoming increasingly difficult. Impedance-based DES modeling emerged as an effective technique as it reduces the system into source and load subsystems and offers easier analysis of the dynamic interactions between them. These models can be obtained using either analytical calculations, simulations, or experimental measurements. In this work, firstly, a line-to-line current injection technique is used for the measurement of alternating current (AC) impedances. Since it requires repeated injections, a d q -domain impedance measurement methodology based upon a set of independent perturbations and measurements is proposed. The perturbation is injected via a sweep signal which is preprocessed by the digital signal processor (DSP) prior to injection. The d q reference frame is synchronized with the three-phase AC system using a low-bandwidth phase-locked loop (PLL). The close matching of impedance parameters measured in simulation using the proposed approach with those obtained using analytical expressions and the line-to-line current injection technique verifies the effectiveness of the approach. Furthermore, the method was also implemented experimentally, and the close matching of the results with the analytical and simulation results validates the overall modeling and measurement procedure.

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Li, Liran, Zhiwu Huang, Heng Li, Xiaohui Qu, and Jun Peng. "A Highly Efficient and Reliable Power Scheme Using Improved Push-Pull Forward Converter for Heavy-Duty Train Applications." Journal of Advanced Computational Intelligence and Intelligent Informatics 20, no. 2 (March 18, 2016): 342–54. http://dx.doi.org/10.20965/jaciii.2016.p0342.

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Electronically controlled pneumatic (ECP) brake systems have become popular in heavy-duty train applications because of their advantages, which include shorter stopping distances, improved handling, and less brake-shoe and wheel wear. In ECP brake systems, an improved power supply is required to support efficient and reliable operations. In this paper, we propose a new power converter for ECP brake systems, which is derived from a conventional push-pull converter. As opposed to conventional push-pull converters, we insert a clamping capacitor into the proposed circuit. This clamping capacitor simultaneously enables a greater number of operation modes for the proposed converter and absorbs the voltage spikes in the switch. The proposed converter is more suited for ECP brake applications that require high power, low voltage ripple, and high impedance. We theoretically analyze the proposed converter, and present the design guidelines. Further, we discuss the modeling and control aspects. We demonstrate the operations of the proposed model by performing both simulations and experiments.

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Pastor Torrico Bascopé, René, Grover Victor Torrico-Bascopé, Francisco José Barbosa de Brito Júnior, and Sérgio Daher. "Multi-state And Interleaved Converters With Passive Impedances For Current Sharing." Eletrônica de Potência 19, no. 3 (August 1, 2014): 252–59. http://dx.doi.org/10.18618/rep.2014.3.252259.

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Wang, Rutian, Yuyang Wu, Guoqing He, Ying Lv, Jiaxing Du, and Yanhao Li. "Impedance Modeling and Stability Analysis for Cascade System of Three-Phase PWM Rectifier and LLC Resonant Converter." Energies 11, no. 11 (November 6, 2018): 3050. http://dx.doi.org/10.3390/en11113050.

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In this paper; the impedance model of PWM rectifier and LLC resonant converter are deduced, and the stability analysis of cascade system is studied. The principle of three-phase PWM rectifier is introduced; and the small signal model in d-q coordinate system is deduced. The expression of dc side output impedance model for PWM rectifier is derived. The LLC resonant converter is operated in a fixed-frequency state, and the LLC resonant converter is modeled as a small signal model. On this basis, the input impedance model expression of the LLC resonant converter is derived. According to the impedance stability criterion, it can seen that the amplitude of input impedance is greater than the amplitude of output impedance in a certain frequency domain. In addition, the Nyquist curve is not around the point (−1,0), which can judge that the cascade system is stable. In simulation software, a cascade system simulation is built and corresponding simulation curves are obtained, which verifies the stability of the cascade system.

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Chub, Andrii, Dmitri Vinnikov, Oleksandr Korkh, Tanel Jalakas, and Galina Demidova. "Wide-Range Operation of High Step-Up DC-DC Converters with Multimode Rectifiers." Electronics 10, no. 8 (April 12, 2021): 914. http://dx.doi.org/10.3390/electronics10080914.

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This paper discusses the essence and application specifics of the multimode rectifiers in high step-up DC-DC converters. It presents an overview of existing multimode rectifiers. Their use enables operation in the wide input voltage range needed in highly demanding applications. Owing to the rectifier mode changes, the converter duty cycle can be restricted to a range with a favorable efficiency. It is shown that the performance of such converters depends on the front-end inverter type. The study considers current- and impedance-source front-end topologies, as they are the most relevant in high step-up applications. It is explained why the full- and half-bridge implementations provide essentially different performances. Unlike the half-bridge, the full-bridge implementation shows step changes in efficiency during the rectifier mode changes, which could compromise the long-term reliability of the converter. The theoretical predictions are corroborated by experimental examples to compare performance with different boost front-end inverters.

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Verma, Deepak, S. Nema, and A. M. Shandilya. "A Different Approach to Design Non-Isolated DC–DC Converters for Maximum Power Point Tracking in Solar Photovoltaic Systems." Journal of Circuits, Systems and Computers 25, no. 08 (May 17, 2016): 1630004. http://dx.doi.org/10.1142/s021812661630004x.

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Maximum power point tracking (MPPT) is an essential part of solar photovoltaic (PV) system to draw maximum available power which is generated by the solar PV. The concept of MPPT is based on maximum power transfer theorem. When the impedance of source is equal to the load impedance then only, source or solar PV delivers maximum power to the load. Impedance matching is done through DC–DC converter, whereas the duty cycle of the converter is decided by the MPPT algorithm. Nonetheless, DC–DC converter design is a key aspect in any tracking scheme, bulk of publications on MPPT are available in literature but very less information can be obtained on DC–DC converter design. Thus, the main focus of this paper is to provide an easy converter design procedure for MPPT in solar PV applications on the basis of solar panels impedance. In this paper, a step by step design of buck converter, boost converter and buck–boost converter particularly for MPPT applications is presented and results are verified through OPAL-RT OP4500 Real Time Simulator.

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de Souza, Victor Ramon França Bezerra, Luciano Sales Barros, and Flavio Bezerra Costa. "Modular Multilevel Converter for Low-Voltage Ride-Through Support in AC Networks." Energies 14, no. 17 (August 27, 2021): 5314. http://dx.doi.org/10.3390/en14175314.

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New grid-connected systems have imposed additional requirements regarding reliability, power quality, high levels of power processing capacity, and fault support, where power converters have a crucial role in fulfilling these requirements. Overcoming one of these challenges, this paper proposes a new alternative application to improve the low-voltage ride-through (LVRT) support based on the arm impedance employment of the modular multilevel converter (MMC) by attenuating the fault impacts, avoiding overcurrents and overvoltages. This proposal does not require additional hardware or control loops for LVRT support, only using PI controllers. This paper evaluates symmetrical and asymmetrical grid fault impacts on the converter DC side of four converter topologies: two-level voltage source converter topology (2L-VSC), neutral point clamped (NPC), MMC, and 2L-VSC equipped with a DC-chopper, employing the same control structure for the four topologies, highlighting that the MMC contributed better to LVRT improvement under severe grid conditions.

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Journal articles on the topic 'Impedance convertor'

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