Stability-Margin-Oriented Key Parameter Design for Voltage-Source Rectifiers in Weak Power Grids With Inductive Impedance

Voltage-source rectifiers (VSRs) have been widely used in modern power grids. The inductive grid impedance of the power grid poses a serious threat to the stability of the VSR. To guarantee the stability of the VSR, the inductive grid impedance must be considered when designing the controller parameters. In this article, a stability-margin-oriented design method for the controller parameters of the VSR in the weak power grid with an inductive grid impedance is proposed, where the inductive impedance value can be significant in practice. Firstly, the proportional gain of the dc-link voltage controller is designed based on the Routh Criterion to obtain the required gain margin. Then, regarding the lack of the phase margin, the grid-voltage feedforward gain is designed for improving the phase margin based on the singular value of the system. Furthermore, it is found that the lack of the phase margin is very serious in the system with multiple VSRs in parallel. Therefore, the stability margin of the system when connecting multiple VSRs with the designed parameters is investigated, and the effectiveness of the proposed design method in this article on guaranteeing the phase margin and the gain margin of the system is confirmed. The proposed design method in this article has the merit that it can guarantee the stable operation of the multiple VSRs in parallel which are connected to the weak power grids with various short circuit ratios. Moreover, the dynamic response of the VSR with the designed parameters is explored, and the stability of using the load power feedforward for improving the dynamic response of the VSR connected to the power grid with a large impedance is confirmed. Simulation and experimental results have been provided, the effectiveness of the design method proposed in this article.