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Short-term Frequency Support Method for a Single-stage Photovoltaic Generator based on Residual Voltage Control

At present, PV generation has made encouraging developments with short-term frequency support technology suppressing the disturbance of frequency without external energy storage. However, it is urgent for PV generators to deal with the second drop in frequency when the capacitor runs out and loses support capability. This paper proposed a residual voltage control based short-term frequency support method for a single-stage PV generator. The residual voltage of the capacitor is controlled by considering the actual DC voltage to calculate the voltage reference, besides the difference between the actual frequency and its reference. Consequently, the capacitor can achieve a smooth transition of the voltage before exhausted. The performance of the proposed method is evaluated with EMTP-RV generated data, considering different frequency drop and capacitance of the PV generator. The results indicate that the proposed method can achieve a better frequency nadir without a second frequency dip.