An improved method of phase-locked loop grid-connected inverter based on capacitor voltage full feedforward

Abstract

Different from the conventional grid voltage feedforward, the capacitive voltage type full feedforward will not amplify high frequency harmonics, and it can eliminate the capacitor current control and simplify the controller design. However, when the grid impedance is relatively large, the phase-locked loop may increase the current harmonics of the grid-connected inverter, leading to system instability. Therefore, this paper establishes the output impedance model of the grid-connected inverter with full feedforward capacitor voltage including phase-locked loop, and then proposes an improved strategy for adding a low-pass filter in the traditional phase-locked loop, and parameterizes it *Design, so as to achieve the purpose of improving the output impedance phase of the inverter. Finally, the simulation verifies that the inverter using the improved phase-locked loop can effectively improve the quality of the grid current and improve the stability of the inverter system in a weak grid.