Low Voltage Ride-through Performance of Direct-Driven Permanent Magnet Wind Turbine under Improved Control Strategy

As for the direct-driven permanent magnet wind turbines,the integration of non-controlled rectifier,DC boost,PWM and inverter,an improved power flow control strategy is proposed.In case of the grid voltage sags,the generator-side active power is reduced to ensure the stability of the DC-side voltage,and meanwhile the reactive power is transmitted to the grid.As simulation results indicate,in case of three-phase symmetrical faults,the proposed strategy can effectively guarantee the power balance between generator side and grid side,and also increase the output voltage level of the grid-connected inverter,thus greatly improving the low voltage ride-through performance of the wind turbine.