Control Method for Coordinated Power Frequency Modulation and DC Voltage Recovery in Grid-Connected Photovoltaic System

This paper proposes a combination control method of photovoltaic (PV) arrays and DC link capacitors to participate in grid frequency modulation. An improved PV power reserves control (PRC) is proposed to fully utilize the available PV power to compensate for the DC voltage shortage caused by virtual inertia control (VIC). This method improves the available frequency modulation of the PV system. It restores the frequency support capability by utilizing the power margin in the system when the system frequency cannot be restored to the rated value. The simulation in MATLAB/Simulink compares the frequency modulation effect under different load variations or capacitors between the proposed method and traditional VIC. The problem of unrecoverable DC voltage and the performance of frequency dip suppression are considered.