STATCOM is a flexible AC transmission device which has been widely used and studied for a long time. The performance improvement and cost reduction of the STACOM are always the focus in the research. Based on the analysis of the output characteristic of the phase detector of the typical Park transformation of three-phase phase locked loop

a novel three-phase PLL with instantaneous response is proposed to improve the transient performance of the STATCOM DC voltage and enhance the utilization rate of DC capacitor or IGBT by way of reducing the DC capacitance or increasing the DC voltage. The equivalent simulation system of three-phase bridge STATCOM and chain cascaded STATCOM are set up respectively in PSCAD software. Such small disturbances as step of reactive current instruction

amplitude of grid voltage

step of phase angle and frequency and such big disturbance as short circuit fault of grid are systematically simulated and analyzed. The simulation analysis comparison result shows that in case of remarkable change of voltage phase angle of common connection point of the SATCOM during the disturbance

the DC voltage control characteristic of the new method is more superior to the traditional method

the response speed of the reactive power increase slightly and the electrical stress of the DC capacitor can be reduced significantly.