A Coordinated Control Strategy of Voltage and Frequency for Doubly-fed Wind Power Generation System Connected to Flexible HVDC Grid

In allusion to the doubly-fed wind power generation system connected with flexible HVDC transmission grid, a coordinated control strategy based on rotor side converter and HVDC grid side converter, which made the stator frequency and stator voltage changed with wind speed in a wider range, was proposed, to implement high efficient operation of doubly-fed wind power generator. Under the scene of traditional topology, by which a traditional doubly-fed wind power generation set was connected with flexible HVDC transmission grid, the simulation of the wide range voltage-frequency coordinated control strategy of a single 1.5 MW doubly-fed wind power generation set was conducted. When the wind speed varied, by means of controlling the converter at HVDC grid side the frequency of stator current was correspondingly adjusted, at the same time, the rotor side converter magnetic chain loop was controlled to make the stator magnetic chain kept constant, thereby, the stator voltage varied in the same proportion, thus within the full wind speed range the iron loss of the doubly-fed wind turbine could be decreased. Simulation results show that within the full wind speed range the wide-range voltage and frequency coordinated control strategy can be realized, besides, comparing with constant voltage and constant frequency control strategy the overall efficiency of doubly-fed wind power generation set can be evidently improved.