基于撬棒保护的双馈风电机组动态特性分析

Dynamic Characteristic Analysis of Doubly-Fed Induction Generator Based on Crowbar Protection

撬棒保护是双馈风电机组提高的低电压穿越能力的主要措施,它可以用来保护转子侧变流器,改善风机的动态特性,使其达到电网公司及运营商提出的并网要求。而撬棒保护的投切时间对双馈机的低电压穿越性能影响较大,通过瞬时故障分析初步得到了撬棒保护较理想退出时间。对于50%和20%两种不同的电压跌落程度并持续625ms的故障测试结果显示,当电压跌落至20%时,保护退出的理想时间要适当提前一个周波,即故障持续时间和故障的影响程度将对撬棒保护的控制策略产生影响。

Crowbar protection circuit is frequently adopted to implement low voltage ride through （LVRT） of doubly fed induction generator （DFIG） driven by grid-connected wind turbine. The DFIG system with crowbar can protect the converter against overvoltage and overcurrent to meet the requirement of grid companies and operators. The LVRT effect is greatly influenced by the resistance and quitting time of the crowbar. We initially achieve ideal crowbar quitting time through the analysis of the transient fault. Voltage dip faults of 50% and 80% with a duration of 625ms have been tested. The result shows that when grid voltage balancing drops to 20% and last 625ms, the quitting time of the crowbar should be brought forward a cycle, which implies that the duration of the fault and voltage sag levels influence the LVRT control strategy.