Operation Characteristics Analysis of Power Synchronization Control Under Frequency Drop

With the increasing integration of renewable energy, the traditional generating units are gradually replaced by voltage source converters (VSCs). VSCs using the traditional current control strategy based on phase-locked loop (PLL) can't provide active power support and frequency regulation under frequency drop. In this paper, power synchronization control (PSC) is applied to substitute the PLL. The PSC output phase and the active power generated by the converter are analyzed when the net frequency decreases. It is proved that, during frequency drop, the PSC output phase leads the phase of the grid voltage at a fixed angle and the converter output power can respond to the change of frequency inherently. In addition, an improved control strategy is proposed to further improve the active support capability of the converter. The theoretical analyses and the effectiveness of the improved control strategy are verified by time simulations.