Optimal Design of DC Capacitance of Photovoltaic Self-Synchronizing Voltage Source

The self-synchronous voltage source inverter is similar in external characteristics to a synchronous generator and has an excellent performance in frequency and voltage regulation. In the scenario of grid-forming, the output power of the photovoltaic self-synchronizing voltage source is insufficient due to the inherent intermittent light disturbance, which is easy to cause DC undervoltage and even system shutdown accidents. DC capacitor energy storage can bear the output power shortage during light disturbance for a short time, provide sufficient time support for inverter output power regulation, and avoid undervoltage accidents. For this reason, this paper proposes an optimal design method of capacitance parameters based on the DC voltage transient model. This method realizes the accurate description of DC voltage fluctuations based on the inverter transient model, establishes the numerical relationship between lighting disturbance and DC voltage fluctuations under different capacitance parameters, and finally realizes the optimal design of capacitance. The simulation results show that the proposed method can provide 100-millisecond support for the inverter output power regulation during the light disturbance, effectively alleviate the DC voltage drop, and improve the DC side voltage stability of the inverter.