双馈风机故障穿越短路电流计算方法

Research on calculation method for short-circuit current of doubly-fed induction generator during fault ride-through

双馈风电场故障穿越短路电流控制策略和保护电路比较复杂,导致现有短路计算过程繁琐、短路电流计算精确度不足,对当地电网的安全运行产生了较大影响。为了应对这一挑战,提出一种短路电流统一计算方法,以实现双馈风机故障穿越期间输出短路电流的精确数学解析计算。所提出的方法主要包括:1)充分考虑故障穿越期间的不同内部保护电路和控制策略,并建立全过程统一状态空间模型,故障穿越全过程包括撬棒保护阶段、去磁控制阶段和无功电流补偿阶段;2)建立基于定子电压和定子磁链的统一状态空间模型和定子输出短路电流计算方法;3)基于时频时域的拉普拉斯变换揭示了定子侧和网侧变流器的故障电流贡献机制,并将其表示为统一的短路电流表达式。大量测试结果验证了所提出方法的正确性和有效性。

The fault ride-through fault current control strategies and protection circuits of DFIG wind farms are rather complicated,which results in the existing fault current calculation process being cumbersome and the fault circuit current calculation accuracy being insufficient,which has a great impact on the safe operation of the local power grid.In order to tackle this challenge,a unified fault current calculation method is proposed to achieve accurate mathematical analytical calculation of the output fault current of doubly fed induction generator during fault ride-through.The proposed method mainly includes:1)Unified state space model of the whole fault ride-through process is established by fully considering the different internal protection circuits and control strategies during fault ride-through.The whole fault ride-through process includes the crowbar protection stage,the demagnetization control stage,and the reactive current supporting stage;2)Stator output fault current calculation method,is established by a unified state space model based on stator voltage and stator flux linkage;3)Stator-side and grid-side converter fault current contribution mechanism is revealed in a unified fault current expression by Laplace transform through time-frequency-time domain.A large number of test results verify the correctness and effectiveness of the proposed method.