Parameter Design for DC Voltage Loop Regulator and Phase-Locked Loop Regulator of Grid-Connected Inverter Under Weak Grid

In the grid-connected inverter (GCI), the de voltage loop (DCVL) and the phase-locked loop (PLL) are utilized to generate the amplitude and phase reference for the current control loop, respectively. These two control loops introduce two additional admittances at the output port of the grid-connected inverter which are influenced by the steady-state value of the grid currents. It significantly influences the admittance characteristics of the grid-connected inverter and the stability of the gridconnected inverter in weak grid. Therefore, this paper establishes the model of the grid-connected inverter and derives its output admittance. Subsequently, the impact of the steady-state values of the grid currents on the stability of the grid-connected inverter is analyzed and the parameters of the PLL regulator and DCVL regulator are designed. Finally, a grid-connected inverter simulation model is built, and the simulation results verify the accuracy of the stability analysis and the correctness of parameter design results.