电压不对称骤升时DFIG暂态特性分析及控制策略改进

Analysis of DFIG Transient Characteristics and Improvement of Control Strategy in Case of Voltage Asymmetry Swell

针对双馈感应风力发电机(DFIG)故障穿越问题,传统的研究大多只单独考虑电压对称下降或上升情况,但电压的恢复过程往往伴随着电压的升高,因此研究含电压下降和上升的不对称故障尤为重要。对两种典型不对称骤升故障期间的DFIG瞬态特性进行了理论推导,给出定子磁链变化规律;在此基础上,针对双闭环控制无法抑制故障期间转子电流和直流母线电压越限问题、Crowbar保护带来的电机失控问题等,提出一种定子串电阻改进控制策略。仿真结果验证了理论分析的正确性,所提控制策略改善了DFIG的瞬态响应,有利于故障电网的恢复。

Aiming at the problem of doubly-fed induction generator(DFIG)fault ride through,most of the traditional researches only consider the symmetrical voltage drop or rise,but the recovery process of grid voltage is often accompanied by voltage rise,so it is particularly important to study the asymmetric fault with voltage drop and swell.The transient characteristics of DFIG under two typical asymmetric sudden rise faults were theoretically derived,and the variation law of stator flux was given;on this basis,an improved control strategy of stator series resistance was proposed to solve the problem that the double closed-loop control can not restrain the rotor current and DC bus voltage is out of limit in the process of fault,and the motor is out of control caused by Crowbar protection.The simulation results verify the correctness of the theoretical analysis,and the proposed control strategy improves the transient response of DFIG,which is conducive to the restoration of grid voltage.