Design and Research of a 10 kV Dynamic Voltage Restorer based on Cascaded H-Bridge and Supercapacitors

Voltage sag has become one of the key power quality problems for sensitive loads. To cope with high voltage level and large capacity demand for 10kV voltage sag mitigation schemes, this paper proposes and studies in detail a 10kV hybrid Dynamic Voltage Restorer (DVR) based on back-to-back cascaded H-bridge converter with supercapacitors as energy storage elements. The optimization on topology makes it suitable for sag compensation scenario. The optimized design of injection power coordination control enlarges DVR compensation range by rationally manage the rectifiers' power absorption from grid and supercapacitors' discharging. The design of redundant operation control contributes to a flexible operation and back-up redundancy for converter submodules. The simulation result based on PLECS environment together with a down-scaled experimental prototype have verified the correctness and effectiveness of proposed control schemes, the comparison among parallel energy storage scheme, series DVR scheme and proposed scheme proves the advantages of larger compensation range, better grid adaptability and less energy storage consumption.