Grid-Connected Current Double Loop Feedback Suppression Strategy of Parallel Inverter in the Weak Grid

Distributed photovoltaic power generation system operates under weak current network. When multiple inverters are connected in parallel, the equivalent impedance decreases, and the resonant frequency of coupled resonance generated by parallel operation migrates to low frequency, which is not conducive to the stable operation of power grid. In order to suppress the resonance phenomenon when multiple inverters are connected to the grid, firstly, the equivalent admittance model of multiple inverters under the capacitive current feedback strategy and inverter side current feedback are studied by using the idea of Norton equivalence. It is analyzed that the high-frequency resonance peak amplitude of the system is large when multiple inverters are running, which reduces the robustness of the system. Then, a current double loop feedback resonance suppression strategy on the grid side of parallel inverters is proposed, which weakens the peak in high frequency band and improves the resonance suppression ability of the system. Finally, using RTLAB semi-physical experiment platform to verify the correctness and effectiveness of the proposed strategy.