A PLL‐equivalent model for low‐frequency stability analysis of voltage source converter connected to weak grid

Abstract This study focuses on stability of weak grid connected voltage source converter (WG‐VSC) in Low‐frequency mode (LFM) (around 1–10 Hz), which is dominated by interactions among phase‐locked loop (PLL), outer control and condition. In order to clearly reveal LFM mechanism WG‐VSC, a simple but effective PLL‐equivalent model has been proposed. First, generic small signal consisted PLL ‘outer & WG’ two parts derived. Then, the transfer function complicated part divided into parallel channels, representing impact active side reactive WG‐VSC respectively. Finally, based multi‐mode decomposition theory, second (E‐PLL) obtained for analysis WG‐VSC. The effectiveness E‐PLL verified simulation results PSCAD/EMTDC experimental hardware platform.