Admittance-Based Stability Analysis of Resistance-Emulating Controlled Grid-Connected Voltage Source Rectifiers

Due to low cost and high reliability, resistance-emulating control (REC) is an emerging approach for grid-connected voltage source rectifiers (VSRs). However, small-signal stability issues of the grid-connected VSR with REC are currently rarely studied. In this article, the small-signal dq-admittance model of the grid-connected VSR with REC is first built and the small-signal stability superiority of the VSR with REC in weak-grid connection is revealed. First, a dq-admittance model of the grid-connected VSR with REC is established. The admittance characteristics of the grid-connected VSR with REC and the grid-connected VSR with traditional dual closed-loop control (DCC) are analyzed and compared. Then, the influence of short circuit ratio (SCR), voltage-loop bandwidth, and the output power on the stability of the VSR with REC and DCC is analyzed based on the generalized Nyquist criterion. The stability comparison results indicate that the VSR with REC has better adaptability to the weak grid and can achieve a higher bandwidth at the voltage loop. Besides, it is found that the DCC controlled VSR is more suitable for light-load operation than the REC controlled VSR. Finally, the correctness of the analysis is verified by experiments.