Frequency regulation method for two-stage PV system based on DC voltage coordination.

• A frequency regulation method for a two-stage PV system by controlling DC voltage is proposed, which is coordinated with the enhanced virtual inertia control (VIC) of the DC capacitor. • An active DC voltage recovery control is designed at the inverter to restore the frequency support ability after primary frequency modulation. • The proposed method can fully use the available power to improve the frequency nadir, rate of change of frequency, and voltage recovery ability. The current frequency regulation methods for a photovoltaic (PV) system cannot balance frequency support and primary control performances. This paper proposes a frequency regulation method for a two-stage PV system by controlling DC voltage, which is coordinated with the enhanced virtual inertia control (VIC) of the DC capacitor. The power reserve control of the PV arrays is improved considering the characteristics of the VIC, thereby strengthening the frequency regulation ability of the PV system. An active DC voltage recovery control is designed at the inverter to restore the frequency support ability after primary frequency control. With MATLAB/Simulink software, the performance of the proposed method in dealing with different load sizes, load change trends, and DC voltage recovery coefficient is verified by comparing it with other traditional methods in different scenarios. The proposed method can fully use the available power to improve the frequency nadir, rate of change of frequency, and voltage recovery ability. [ABSTRACT FROM AUTHOR]