Transient Fault Current Analysis of the Inverter-interfaced Renewable Energy Sources Considering the Dynamic Characteristics of the Phase-locked Loop

The existing short-circuit fault analyses of the inverter-interfaced renewable energy sources (IIRESs) lack quantitative consideration for the nonlinear links of the control system during the fault transient. Thus, the analytical accuracy of the transient current cannot be guaranteed. To fully characterize the fault transient features of the IIRESs, a time-domain transient fault current analysis method for the IIRESs considering the dynamic features of the phase-locked loop (PLL) is proposed. The PLL fault transient features and the relevant influences on the dynamic characteristics of the current loop are first analyzed in detail. Then, the formal decoupling mathematical method in plural domain is utilized to deduce the transient current in dq coupling scenario caused by the static error between the PLL output and the feedforward compensation's angular frequencies. Further, by tracing points according to the time sections, the nonlinear fault current analysis issue under the PLL's dynamic features is solved. Compared with the published works, the influence mechanism of PLL nonlinear output on the transient current is revealed according to the proposed method, and the underdamped oscillation attenuation features of the transient fault current are characterized. The simulation results and the field site data verify the effectiveness and accuracy of the proposed method. © 2021, Power System Technology Press. All right reserved.