电网短路故障时交流励磁风力发电机不脱网运行的励磁控制策略

Ride-through Control Strategy of AC Excited Wind-power Generator for Grid Short-circuit Fault

提出一种电网短路故障时保持交流励磁风力发电机不脱网运行的新型励磁控制策略。分析了电网短路故障时交流励磁发电机的暂态物理过程和转子过电流的原因。改进控制方案从限制电网故障时定子工频过电流的角度出发,有效限制了由定子电流工频分量引起的转子电流交流分量,同时利用发电机定子电阻对定子磁链暂态直流分量进行灭磁,实现了故障时避免转子出现过电流的目的。建立了2MW商用交流励磁风力发电系统仿真模型,在电网对称故障和非对称故障条件下,对"crowbar protection"方案和该文所提方案进行了仿真对比研究。仿真结果验证了该文所提改进方案的有效性,实现了电网故障期间发电机转子励磁变频器的安全运行,提高了交流励磁风力发电系统在电网故障时的不间断运行能力。

A new excitation control strategy is proposed for the rotor side converter in an AC excited wind-power generator to allow the system to ride through the grid short-circuit fault. The transient physical course of the AC excited generator （ACEG） and the reason for the rotor over current during the fault are analyzed. In order to avoid the over current in the rotor during the fault, the rotor current AC components produced by the stator currents at 50Hz have been successfully restrained and the stator resistance is also used to demagnetize the machine. A commercial 2 MW AC excited wind-power generation simulation system is set up. Compared with the traditional ＇crowbar protection＇ strategy, the proposed control strategy is validated by the simulation results under the grid symmetrical and unsymmetrical fault conditions. The rotor excitation converter has been successfully protected during the grid fault and it improves the fault ride-through ability of the AC excited wind-power generation system.