Impedance-Based Analysis of Control Interactions in Weak-Grid-Tied PMSG Wind Turbines

The frequent oscillations in the weak-grid-tied permanent magnet synchronous generator (PMSG) wind farms can severely deteriorate the power system security. The impedance-based method is widely applied but limited to optimize the system, where the PMSG is regarded as a black box and only the external output characteristics are reflected. In this article, a novel impedance-based analytical approach is proposed to analyze the weak-grid-tied PMSG wind farms from a control interaction perspective, to complement existing studies. The shaping effect of the interactions among various controllers on the impedance of PMSG is analyzed, including the phase-locked loop (PLL), the voltage control loop and the current control loop. Based on the analytical analysis, an optimization method is then devised to appropriately design the parameters of the voltage control loop and improve the system stability margin. Time-domain simulation results in Matlab/Simulink verify the efficacy of the proposed method. The outcome of this study can provide useful guidance on control designs for PMSG-WTs in weak grids.