Control strategy for grid-connected inverter in photovoltaic power generation system

CHEN Rui-rui， CHEN Hui-ming， WANG Zheng-shi
（College of Electrical Engineering， Zhejiang University， Hangzhou 310027， China）

Abstract：Aiming at the problem that traditional PI controller is difficult to track the sinusoidal instruction accurately and to inhibit the grid interference effectively, also, PR controller has weak anti-interference capability in non-resonant frequency area, the control model of inverter in the two-stage photovoltaic power generation system was built. The design principles and detail process of the dual-loop system was given using the frequency-response analysis method. Considering that the system output power changes with the output capacity of PV array, an improved piecewise PI + quasi resonant control algorithm was proposed based on DSP digital control to obtain better system stability and current waveform. A 2 kW experimental prototype was designed to test validity of proposed strategy. The experimental results show that the scheme is simple and stable. The system has good dynamic and static performance. The total harmonic distortion (THD) of the output grid current decrease significantly and the system has strong anti-interference ability.
Key words： photovoltaic power generation sysem； grid-connected； inverter； resonance control； digital control