Photovoltaic Grid-Connected Inverter CCS-MPC Algorithm Based on DSOGI-PLL under Weak Grid

Abstract

In this paper, a continuous control set model predictive control (CCS-MPC) algorithm is proposed for the stability control of photovoltaic grid-connected inverters in weak grids. Due to the problem that the impedance of the power grid cannot be ignored under the weak power grid, the stability of the power grid is reduced. Therefore, this paper will study the stability of three-phase grid-connected inverters in weak grids. In view of the problem that the phase-locked loop will be disturbed in the weak power grid, this paper use a phase-locked loop based on a biquad generalized integrator (DSOGI-PLL) to achieve precise phase-locking. MATLAB/Simulink is used to build the simulation model of three-phase grid-connected inverter, and analyze the output of three phase current after different impedance mutation. The difference is significantly smaller than the traditional PI control algorithm, which can improve the quality of the output voltage of the inverter and maintain the stability of the system.