Application of UIPC to improve power system stability and LVRT capability of SCIG-based wind farms

This study discusses the possibility of the connection of squirrel cage induction generator (SCIG)-based wind farms (WFs) to power system through unified inter-phase power controller (UIPC) to improve the low-voltage ride-through (LVRT) capability of WF and enhance the power system stability. The UIPC is based on inter-phase power controller (IPC), where its phase-shifting transforms (PSTs) are replaced by two series converters (SECs) and one shunt converter (SHC). The operation of the UIPC is divided into normal and LVRT operation modes. In normal operation mode, the UIPC injects the total active power generated by the WF to power system and controls the power factor of the UIPC connecting point (CP) by reactive power control. In LVRT mode, the WF which is connected through UIPC, acts as a flexible AC transmission system device with capability of active and reactive power controls at CP. In this study, the UIPC model is developed based on phase angles of injected SECs voltage and a unified control scheme including UIPC SECs, UIPC SHC and pitch angle control of wind turbine, is proposed to improve LVRT capability of WF and power system stability during faults. Also, the impact of the simultaneous application of the IPC and static synchronous compensator is studied and compared with the application of the UIPC for connecting the SCIG-based WFs to the power system. The PSCAD/EMTDC simulation results show that the UIPC presents an effective solution for connecting WFs to power system.