基于时域动态过程的变速抽蓄机组外部故障短路电流计算方法

变速抽蓄机组（VSPSU）采用特殊的交流励磁结构及控制方式，导致其外部故障短路特性与常规定速机组相比差异巨大。为此，提出了一种基于时域动态过程的外部故障短路电流计算方法。根据VSPSU外部故障下的励磁及控制特点，将外部故障下的VSPSU分为持续励磁和跨接器动作这2种情况，并基于空间矢量分析分别建立2种情况下的时域动态电路模型。在此基础上，结合2种情况的过渡边界条件和定子磁链动态特性推导得到VSPSU外部故障短路电流的解析表达式。与PSCAD/EMTDC仿真结果的对比表明，所提出的VSPSU外部故障短路电流计算方法具有较高的准确性及实用价值，能满足变速抽水蓄能电站一次设备选型以及继电保护等工作的需要。

Calculation method of external fault short circuit current of variable speed pumped storage unit based on time-domain dynamic process

The variable speed pumped storage unit(VSPSU) adopts a special AC excitation structure and control method, which results in a huge difference in its external fault short circuit characteristics compared with the conventional fixed speed units. Therefore, a calculation method of short circuit current under external fault based on time-domain dynamic process is proposed. According to the excitation and control characteristics of VSPSU under external fault, the VSPSU under external fault is divided into two cases: continuous excitation and crowbar action. Based on space vector analysis, the time-domain dynamic circuit models are established respectively. On this basis, the analytical formula of the external fault short circuit current of VSPSU is derived by combining the transition boundary conditions of the two cases and the dynamic characteristics of the stator flux linkage. Comparison with simulative results by PSCAD/EMTDC shows that the proposed calculation method of short circuit current under VSPSU external fault has high accuracy and practical value, which can meet the needs of primary equipment selection and relay protection of variable speed pumped storage power plant and so on.