A low voltage ride-through rapid reactive power control method for a PV inverter based on phase compensation of a phase-locked loop
DOI：10.19783/j.cnki.pspc.240019
Key Words:PV inverter  phase-locked loop  phase compensation  feed-forward control  low voltage ride through  transient reactive power characteristic
Author NameAffiliation
GOU Yiyun Department of Electrical Engineering, Tsinghua University, Beijing 100084, China 
ZHENG Jinghong Department of Electrical Engineering, Tsinghua University, Beijing 100084, China 
LIU Zhuang Department of Electrical Engineering, Tsinghua University, Beijing 100084, China 
DING Yusheng Department of Electrical Engineering, Tsinghua University, Beijing 100084, China 
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Abstract:There can be a problem of transient overvoltage caused by the slow reactive power retrace speed of a PV grid-connected system with a weak power grid in the voltage recovery stage. Thus this paper presents an improved control strategy of fast reactive power for a PV inverter based on phase-locked loop (PLL) phase compensation. First, the reasons for the slow reactive power recovery speed of PV inverters are analyzed from the aspects of phase jump, PLL dynamics and power grid strength. Then, from a mechanism analysis of the relationship between modulating voltage of PV inverters and the phase angle of PLL, an improved PLL control strategy based on phase compensation is proposed. From the requirements of reactive power control, a method of determining the compensation phase is derived. A electromagnetic transient simulation model of the photovoltaic grid-connected system is established, and the effectiveness of the proposed improved control strategy is verified in three phase symmetric, asymmetric, line cutting and other fault scenarios. Finally, based on RT-Lab, a hardware-in-loop simulation platform of a PV grid-connected system is built to further verify the effectiveness of the improved control strategy. The control strategy enables the PV inverter to obtain faster reactive power recovery, and can effectively suppress the transient overvoltage problem in the low voltage fault recovery stage.
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