Analysis of Short-Circuit Fault Voltage Support Mechanism of Power Electronized Power System

Power electronized resources (PERs) represented by wind power and photovoltaic are rapidly replacing synchronous generators (SGs). Different from the synchronous machine, the overcurrent capacity of PER is low which results in limited voltage support capability during short circuit faults. Moreover, PER operates in current limiting mode as a controlled current source under severe faults, whose phase is controlled based on the phase of PCC measured by a phase-locked loop (PLL) and the dq axis current can be flexibly controlled. However, the phases of PCCs of different PERs are different, and the voltage support that depends on reactive current injection in its coordinate system is not from the system’s perspective. Furthermore, the multi-device coupling characteristics of PER make the fault voltage support complicated. In this paper, mathematically, the voltages of the multi-device system are calculated, and the key influencing factors on the system voltage are extracted from the system perspective. Physically, the influence mechanism of current amplitude and phase of different PERs on the system voltage is analyzed by using the method of phasor analysis. Finally, the influence rule has been verified in a regional power grid with more than 80% renewable energy.