Applied Research of Hexagonal Converter in Full Power Pumped Storage System
In the pumped storage system,the adjustable speed units can adapt to a wider range of water head,im-prove the stability of the unit and optimize the engineering design.As a high-voltage and large-capacity converter,the hexagonal converter(Hex verter)can solve the problems of small capacity of converter,low energy conversion ef-ficiency and slow speed regulation in variable speed pumped storage system.This paper proposes a full-power pumped-storage system based on the hexagonal converter.The positive-sequence,negative-sequence and zero-se-quence networks are mathematically modeled,and the multiple-dq decoupling control strategy based on the two fre-quencies of the grid side and the machine side can realize the power control of the grid side and the machine side,and the output voltage and current frequency of the machine side can be flexibly adjusted.Based on the zero-se-quence network,the branch DC voltage balance control strategy can realize the branch DC voltage equalization.Finally,the effectiveness of the hexagonal converter in the full-power pump-storage system is verified by simulation and experiment.
hexverter topologyvariable-speed pumped-storage system with full-size convertermultiple decoupling and coupling control modelcapacitor voltage balancing