The Experts below are selected from a list of 34365 Experts worldwide ranked by ideXlab platform
Hailin Zhang - One of the best experts on this subject based on the ideXlab platform.
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Analysis and Damping Control of Small-Signal Oscillations for VSC Connected to Weak AC Grid During LVRT
IEEE Transactions on Energy Conversion, 2019Co-Authors: Xuewei Wang, Hailin ZhangAbstract:The instability issues of grid-connected voltage source converters (VSC) may easily occur during low voltage ride-through (LVRT), especially when connected to a weak ac grid. In this study, a small-signal model of the grid-connected VSC system was developed to deal with the stability problems during deep voltage sags. Based on the model, the interaction between the phase-locked Loop (PLL) and Current Control has been illustrated. In addition, the eigenvalue and modal analysis method was employed to investigate the influencing factors of the VSC system stability, which include the bandwidths of the PLL and Current Control Loop, grid strength, and voltage sags. Furthermore, on the basis of the interaction between PLL and Current Control Loop, a novel additional damping Controller that is placed in the active Current Control Loop was proposed and designed. Finally, experiments were conducted to verify the theoretical analysis and proposed Control strategy for enhancing VSC system stability during LVRT with a high impedance grid connection.
Alireza Akhshai - One of the best experts on this subject based on the ideXlab platform.
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a systematic approach to dc bus Control design in single phase grid connected renewable converters
IEEE Transactions on Power Electronics, 2013Co-Authors: Masoud Karimighartemani, Sayed Ali Khajehoddi, Pravee Jai, Alireza AkhshaiAbstract:This paper presents a method for design and Control of dc-bus capacitance and transients in a renewable single-phase grid-connected converter. Conventionally, a proportional (P) or proportional-integrating (PI) Controller is commonly used and the design stage is performed using trial-error or using a simplified analysis that does not take the dynamics of the Current Control Loop into consideration. This paper proposes 1) a systematic and efficient method for design of dc-bus PI Controller gains; and 2) an accurate method for the design of the dc-bus Controller gains without neglecting the dynamics of the Current Control Loop. Two main objectives are to have Control over the amount of output Current harmonics and over the level of bus fluctuations caused by random input power swings. The proposed method is transparent and it provides a convenient and rigorous insight for the designer to properly select the size of dc-bus component and to determine the Controller gains.
Xuewei Wang - One of the best experts on this subject based on the ideXlab platform.
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Analysis and Damping Control of Small-Signal Oscillations for VSC Connected to Weak AC Grid During LVRT
IEEE Transactions on Energy Conversion, 2019Co-Authors: Xuewei Wang, Hailin ZhangAbstract:The instability issues of grid-connected voltage source converters (VSC) may easily occur during low voltage ride-through (LVRT), especially when connected to a weak ac grid. In this study, a small-signal model of the grid-connected VSC system was developed to deal with the stability problems during deep voltage sags. Based on the model, the interaction between the phase-locked Loop (PLL) and Current Control has been illustrated. In addition, the eigenvalue and modal analysis method was employed to investigate the influencing factors of the VSC system stability, which include the bandwidths of the PLL and Current Control Loop, grid strength, and voltage sags. Furthermore, on the basis of the interaction between PLL and Current Control Loop, a novel additional damping Controller that is placed in the active Current Control Loop was proposed and designed. Finally, experiments were conducted to verify the theoretical analysis and proposed Control strategy for enhancing VSC system stability during LVRT with a high impedance grid connection.
Jesus Dovalgandoy - One of the best experts on this subject based on the ideXlab platform.
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passivity based Controller design of grid connected vscs for prevention of electrical resonance instability
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Lennart Harnefors, Ana Vidal, Alejandro G. Yepes, Jesus DovalgandoyAbstract:The time delay in the Current Control Loop of a grid-connected voltage-source converter (VSC) may cause destabilization of electrical resonances in the grid or in the VSC's input filter. Instability is prevented if the input admittance of the VSC can be made passive. This paper presents an analytical Controller design method for obtaining passivity. The method is equally applicable to single- and three-phase systems, i.e., in the latter case, for both stationary- and synchronous-frame Control. Simulations and experiments verify the theoretical results.
Frede Blaabjerg - One of the best experts on this subject based on the ideXlab platform.
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minimum voltage vector injection method for sensorless Control of pmsm for low speed operations
IEEE Transactions on Power Electronics, 2016Co-Authors: Kaiyuan Lu, Sanjeet Dwivedi, Jesper Riber Rosholm, Frede BlaabjergAbstract:In this paper, a simple signal injection method is proposed for sensorless Control of permanent-magnet synchronous machine (PMSM) at a low speed, which ideally requires one voltage vector only for position estimation. The proposed method is easy to implement, resulting in low computation burden. No filters are needed for extracting the high-frequency Current signals for position estimation. The use of low-pass filters (LPFs) in the Current Control Loop to obtain the fundamental Current component is not necessary. Therefore, the Control bandwidth of the inner Current Control Loop may not need to be sacrificed. The proposed method may also be further developed to inject two opposite voltage vectors to reduce the effects of inverter voltage error on the position estimation accuracy. The effectiveness of the proposed method is demonstrated by comparing with other sensorless Control method. Theoretical analysis and experimental results are given for validating the proposed new sensorless Control method.
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dc voltage fluctuation elimination through a dc capacitor Current Control for dfig converters under unbalanced grid voltage conditions
IEEE Transactions on Power Electronics, 2013Co-Authors: Dehong Xu, Frede Blaabjerg, Min ChenAbstract:Unbalanced grid voltage causes a large second-order harmonic Current in the dc-link capacitors as well as dc-voltage fluctuation, which potentially will degrade the lifespan and reliability of the capacitors in voltage source converters. This paper proposes a novel dc-capacitor Current Control method for a grid-side converter (GSC) to eliminate the negative impact of unbalanced grid voltage on the dc-capacitors. In this method, a dc-capacitor Current Control Loop, where a negative-sequence resonant Controller is used to increase the Loop gain, is added to the conventional GSC Current Control Loop. The rejection capability to the unbalanced grid voltage and the stability of the proposed Control system are discussed. The second-order harmonic Current in the dc capacitor as well as dc-voltage fluctuation is very well eliminated. Hence, the dc capacitors will be more reliable under unbalanced grid voltage conditions. A modular implementation method of the proposed Control strategy is developed for the DFIG Controller. Finally, experiments are presented to validate the theoretical analysis.
