A method for determining stability range of grid-side converter parameters of PMSG based on negative feedback modelling of phase-locked loop and outer control loop

Abstract

Direct-drive wind farms are integrated into power grid through power electronic devices, extensively utilizing voltage source converters (VSCs) for grid connection, which has precipitated frequent stability challenges within the grid integration systems of wind farms; it is imperative to properly tune the VSC parameters consequently. In grid-connected VSC system, the interaction between phase-locked loop (PLL) and outer control loop (OCL) has a significant impact on system stability. Therefore, it is essential to account for the interactions when establishing the stability boundaries for VSC parameters. This article proposes a new method to determine the parameter stability range in grid-side converter of direct-drive permanent magnet synchronous generator (PMSG), based on the interactions between PLL and OCL. This method simplifies the modelling process and improves the accuracy of stability range calculations compared to traditional methods. The system is modelled as a negative feedback system with PLL as the forward path and OCL as the feedback path. Both paths include grid dynamics. This modelling approach not only captures the interaction between PLL and OCL, but is also straightforward and clear. Using the Bode diagram, stability mechanism of the system considering interaction between PLL and OCL is studied. The VSC parameter stability criterion of the system is analysed based on the open-loop frequency characteristics of the system. Then an analytical description of the stability range for parameters is provided. Simulation results confirm the effectiveness of our proposed method.