动态调整转子撬棒阻值的双馈风电机组低电压穿越方法

双馈感应发电机(DFIG)等大型电力电子发电设备接入电网,改变了电力系统源端的暂态特性。在系统故障下,为保证DFIG不脱网运行,常采用转子撬棒保护电路完成低电压穿越(LVRT)。DFIG的暂态特性与故障发生时刻和故障程度有关,传统固定阻值的撬棒电路很难保证不同故障下的LVRT。从时域角度推导了撬棒投入后的暂态转子电流表达式,并提出了基于动态调整转子撬棒阻值的DFIG的LVRT方案,制定了转子撬棒自适应控制策略及阻值整定方法。仿真分析了不同电压跌落深度下所提方案的LVRT特性。结果表明,所提方法不仅能够满足不同电压跌落深度下的转子电流和直流母线电压,而且降低了撬棒投入次数及时间。

Low Voltage Ride-through Method of DFIG Based Wind Turbines by Dynamically Adjusting Crowbar Resistance of Rotor

The doubly-fed induction generator(DFIG)on the power grid changes the transient performance of sources in power system. A rotor Crowbar is usually used to realize low voltage ride-through(LVRT)during short-circuit fault. The transient performance of DFIG is determined by the fault inception and the system fault severity. It is hard to achieve LVRT in various degrees of fault severity using the fixed resistance Crowbar. The expression of transient rotor current with Crowbar resister input is deduced. A LVRT scheme of DFIG by dynamically adjusting Crowbar resistance is proposed. An adaptive control strategy and the resistance setting method are given. Applying the scheme proposed, the LVRT performance of DFIG is simulated during different voltage dips. The results show that it is effective to suppress rotor current and DC bus voltage using the scheme proposed. Meanwhile the working time of Crowbar is shortened and action times are cut down.