电网短路时交流励磁风电机组网侧变换器控制策略

电网短路故障时交流励磁用双脉宽调制(PWM)变换器应提供足够的励磁电压实现交流励磁发电机的不间断运行,要求双PWM变换器直流链电压在故障时波动较小。分析并提出一种电网短路故障时交流励磁风电机组电网侧变换器的控制策略,该方案在电压跌落时仅利用电流内环控制电网侧变换器,并于电压正常时采用带前馈的双闭环电压控制策略控制电网侧变换器。通过仿真验证了所提出的方案在电网短路故障发生和切除时稳定控制直流链电压的有效性,为故障过程发电机不脱网励磁控制奠定了基础,同时该方案也能有效保护直流侧电容及提高系统的稳定性。

A Control Strategy of Grid-side Converter for AC Excited Wind Turbine Under Grid Short-circuit Fault

To maintain a certain level of exciting voltage that is needed for AC generators to ride through system short circuit faults,the DC-link voltage fluctuation of the back-to-back pulse width modulation (PWM) converter used in the AC excited generator should be limited in a small range under grid short-circuit fault,and the adequate voltage on the rotor could be provided for ride-through control of the AC excited generator. A control strategy of grid-side converter for AC excited wind turbine under short-circuit fault is analyzed and proposed. A single inner current control loop is proposed for the control of the grid-side converter during a grid voltage dip,and a double closed-loop voltage control strategy with feed forward control is proposed for the control of the grid-side converter when the grid voltage is constant. The proposed control strategy is validated by the simulation results. The DC-link voltage of the excitation power supply can be stably controlled during the fault,and the effect of ride-through control for the generator can be improved. Furthermore,the DC-link capacitor can also be protected and the system stability can be improved during the fault.