Power Emulator of Variable Speed Drive with Grid Frequency Support in Multi-Converter Based Power Grid Emulation System

Variable speed drives (VSDs) have been gaining more popularity in recent years, since they not only improve the motor load performance, but also can provide grid frequency support after a grid disturbance. However, the existing open loop grid frequency control scheme restricts the power support performance provided by VSDs. In this paper, a closed loop primary frequency support scheme adopted by the VSD is proposed for grid frequency enhancement. Additionally, a real-time power emulator for a passive-front-end VSD using a three-phase voltage source converter (VSC) is developed, which is used for analog testing environment. The developed VSD load emulator demonstrates an accurate dynamic performance without sacrificing the computational resources and simulation time. The accuracy of the VSD load emulator has been verified by experimental results. Furthermore, the grid frequency support provided by VSD loads is performed in the multi-converter based hardware test-bed (HTB) by using the proposed VSD power emulator.