Harmonic current suppression of a grid-forming LCL inverter in a weak grid
DOI:10.19783/j.cnki.pspc.240699
Key Words:weak grid  harmonics of the grid  harmonic current suppression  phase compensation  multi-resonant controller
Author NameAffiliation
XIA Lie1 1. School of Automation, Southeast University, Nanjing 210018, China
2. China Electric Power Research Institute, Beijing 100192, China 
CHEN Zhilei2 1. School of Automation, Southeast University, Nanjing 210018, China
2. China Electric Power Research Institute, Beijing 100192, China 
YANG Qingbin2 1. School of Automation, Southeast University, Nanjing 210018, China
2. China Electric Power Research Institute, Beijing 100192, China 
ZHANG Kanjian1 1. School of Automation, Southeast University, Nanjing 210018, China
2. China Electric Power Research Institute, Beijing 100192, China 
SHEN Siheng2 1. School of Automation, Southeast University, Nanjing 210018, China
2. China Electric Power Research Institute, Beijing 100192, China 
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Abstract:To solve the current distortion problem of a grid-forming LCL three-phase four-wire inverter in a weak grid, a harmonic current suppression method based on a phase-compensated multi-resonant controller (PCMRC) feedforward voltage is proposed. First, looking at the output impedance of the grid-forming LCL inverter, an impedance model of the inverter in a weak grid is established. When the traditional unit feedforward voltage is adopted, the shortcomings of the system low output impedance gain and weak harmonic current suppression ability at the harmonic frequency of the grid is analyzed. Then, considering the influence of the active damping loop of the LCL filter, and based on the traditional unit feedforward voltage, the PCMRC feedforward voltage is introduced. The harmonic suppression performance of the proposed method is analyzed by an impedance bode diagram. The main parameters of PCMRC are designed in detail, and the system output impedance and harmonic suppression ability are analyzed. Finally, an experimental platform is established, and the results show that the proposed method can improve the impedance of the inverter at the harmonic frequency of the grid effectively. Therefore the current distortion caused by harmonics of the grid is suppressed, and the system can maintain good stability when the impedance of the grid changes.
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