A Control Strategy of the Grid-side Converter for Directly-driven Wind Turbine With PM Synchronous Generator Under Unbalanced Grid Voltage Level

A mathematical model of the grid-side converter for directly-driven wind turbine with permanent magnet synchronous generator (PMSG) under unbalanced grid conditions is built, the formation mechanism of voltage double-frequency components on DC side is analyzed, and the influence of power ripple of grid-connected reactor on dual current control is discussed. To suppress the voltage double-frequency component on DC side, an orientated dual current control strategy, which is based on positive and negative sequence voltages respectively, is proposed by considering the power ripple on grid-connected reactor, and the correction of power ripple on grid-connected reactor is introduced to revise reference current in control algorithm. Simulation results show that the proposed control strategy can not only effectively control positive and negative sequence currents and depress voltage double-frequency component on DC side, but also can reduce harmonic component of grid-connected current.