电压跌落时感应电动机反馈电流计算及转速影响研究

大容量感应电动机会影响工业配网的短路电流水平,准确计算其反馈电流对系统保护配置及全网短路电流计算具有重要作用。电压跌落时电动机转速变化会影响电动机的反馈电流,不考虑转速变化可能会导致反馈电流计算结果不准确,影响保护的正确动作。利用感应电动机静态等值电路和复常系数线性微分方程组解法求解定转子磁链正负序强制分量和自由分量,进而得到电压跌落时计及转速变化的感应电动机反馈电流计算方法,并进一步探讨了转速对磁链和反馈电流各分量的影响。采用PSCAD/EMTDC仿真软件中感应电动机的5阶动态模型仿真验证了该分析的正确性。

Induction motor feedback current calculation and speed factor analysis

Large capacity induction machines have a great influence on short-circuit current level of industrial distribution network. Accurate calculation of the feedback current plays an important role in protection configuration and short-circuit current calculation. The motor speed changing during voltage drop is an important factor affecting the accuracy of feedback current calculation, regardless of the speed changing may cause error in feedback current calculation and affect the operation of protection. Using the positive and negative sequence steady-state equivalent circuit of induction motor and constant complex coefficient linear differential equations solving process, forced component and free component of stator/rotor flux linkage are solved. Then the induction motor feedback current formula in consideration of speed changing factor is deduced. Furthermore, the influence of speed on each component of the flux and feedback current is analyzed. The correctness of the proposed analysis is verified by the fifth electromagnetic transient model of induction motor in PSCAD/EMTDC simulation software.