基于定子电流微分前馈控制的双馈异步风力发电机低电压穿越复合控制策略

Low Voltage Ride-through Compound Control Strategy of Doubly-fed Induction Generator Based on Stator Current Differential Feedforward Control

双馈异步风力发电机(doubly-fed induction generator, DFIG)对网侧电压扰动比较敏感,其低电压穿越(low voltageride-through,LVRT)措施仍是目前研究的重要问题之一。针对故障期间转子电流过冲而转子侧变流器(rotor sideconverter,RSC)容量有限,且现有软件控制策略无法直接快速抑制故障过电流的问题,提出一种基于定子电流微分前馈控制的风机低电压穿越复合控制方法。在理论分析定子电流微分与转子暂态感应电动势关联关系的基础上,利用前馈控制跟踪精度及响应速度的优势,给出了基于定子电流微分前馈控制的抑制风机转子暂态分量的方案。将通过可观测的定子电流微分项获取到的造成转子电流冲击的干扰量,经前馈控制器直接引入到转子侧变流器的控制电压参考值端,从而达到快速抑制转子过电流的目的。仿真结果表明,所提出的穿越控制方法无需繁琐的观测技术,复合控制策略最大程度发挥了容量有限的变流器抵消暂态感应电动势、抑制转子过电流的作用,有效扩展了机组的可穿越故障范围。研究结果可为双馈异步风力发电机低电压穿越控制提供参考。

Doubly-fed induction generator(DFIG) is sensitive to grid voltage disturbance, and corresponding low voltage ride-through(LVRT) technology is still an important aspect. To solve the contradiction between rotor current overshoot and the limited capacity of rotor side converter(RSC), a new integrated strategy using stator current differential feedforward control is proposed. After analyzing theoretically the vector direction consistency of stator current differential and the rotor transient induced, a new LVRT scheme based on stator current differential feedforward control is established combining the advantages of feedforward control. This strategy regards measurable stator current differential term as an interference capacity causing rotor over-current and adds it to the control voltage of the rotor-side converter which passes the feedforward controller, so as to restrain the rotor over-current directly. Simulation results show that the proposed scheme can make full use of the limited inverter capacity of RSC to restrain the rotor over-current and to buck the transient EMF of rotor, thus effectively expanding the fault range that can ride through. What’s more, the proposed strategy is simple in structure and does not require complex observation technology, which has better applicability. And the compound control strategy will improve the LVRT performance further. The research results can provide references for LVRT control of DFIG.