A delay compensation method based on a biquad filter for an LCL-type grid-connected inverter
DOI：10.19783/j.cnki.pspc.230939
Key Words:active damping  grid-connected inverter  LCL filter  delay compensation  positive damping region  weak grid
Author NameAffiliation
ZHAO Tieying1,2 1. School of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454003, China
2. Henan Key Laboratory of Intelligent Detection and Control of Coal Mine Equipment, Jiaozuo 454003, China 
LI Junran1,2 1. School of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454003, China
2. Henan Key Laboratory of Intelligent Detection and Control of Coal Mine Equipment, Jiaozuo 454003, China 
GAO Ning1,2 1. School of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454003, China
2. Henan Key Laboratory of Intelligent Detection and Control of Coal Mine Equipment, Jiaozuo 454003, China 
TIAN Peijian1,2 1. School of Electrical Engineering and Automation, Henan Polytechnic University, Jiaozuo 454003, China
2. Henan Key Laboratory of Intelligent Detection and Control of Coal Mine Equipment, Jiaozuo 454003, China 
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Abstract:To attenuate the LCL filter resonance peak, capacitor-current-feedback active damping is widely used in an LCL-type grid-connected inverter. Because of the adverse effect introduced by the digital control delay, the performance of capacitor-current-feedback active damping significantly deteriorates. The negative damping region appears from to . This weakens the stability and robustness of the grid-connected inverter against the grid impedance variation. A biquad filter is adopted to insert into the capacitor-current-feedback path to compensate for the phase-lag resulting from the digital control delay. The positive damping region can be expanded to, thus achieving high robustness against grid impedance variation. The proper discrete method is chosen and the system stability after compensation is analyzed. Also, a detailed close-loop parameter design procedure is presented to obtain better control performance. Finally, experimental results are provided to verify the effectiveness of the proposed method and the feasibility of the parameter design procedure.
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