Analysis of Asymmetrical Fault Short-Circuit Currents in PMSG Considering PLL and Current Inner-Loop Transient Processes

Recently, Permanent Magnet Synchronous Generator (PMSG) have accounted for an increasing proportion of wind farms. However, the large-scale grid-connection of new energy sources has led to profound changes in the fault transient process of the power system, and asymmetric faults are the faults with the highest probability of occurrence in the power system, which urgently requires an analysis of the asymmetric fault characteristics of the PMSG. Hence, an analytical method for analyzing the short-circuit current of PMSG with asymmetrical faults considering phase-locked loop and current inner loop is proposed in this paper. Firstly, the time-domain analytical equation of short-circuit current of wind turbine taking into account the sequential switching control is established, and the influence law of control parameters on the response characteristics of short-circuit current is analyzed. Then, the effects of current loop and phase-locked loop (PLL) on the phase of short-circuit current are investigated separately, and the phase of output current is solved in time periods. Finally, the electromagnetic transient simulation model of the PMSG is established, and the validity of the short-circuit current analytical equation is verified by simulation.