10kV配电网串联补偿装置投入引起的电机自激现象研究

Study on Self-excitation of Motor by Switching Series Compensation Device of 10kV Distribution Network

10 kV配电系统中在串联补偿装置接入暂态过程中引起交流电动机自激较为普遍。对于带有串联补偿装置的线路,电动机定子电流和转子电流中均会出现基频50 Hz电流和低频电流,低频自激电流会产生负的电磁转矩抵消部分基频电流产生的转矩,使电动机的平均电磁转矩减小而低于额定转速,电动机无法正常应用,在系统中引起较大的电流振荡。文中使用PSCAD-EMTDC软件建立了两种典型的辐射式结构10 kV配网带异步电机及串补仿真模型,主要针对电机容量、负荷种类以及串补电容值等因素对串联补偿装置投入引起的电机自激现象进行了计算研究,计算出了自激现象产生后的电压、电流、频率,研究了通过削弱电容串补度来测试电机自激的抑制效果。结果表明,电动机发生自激现象将会产生较大的过电压及过电流,通过降低串联补偿装置补偿度,可以抑制次同步谐振的发生,但不可避免会削弱串联补偿装置对系统电压的补偿作用。

In 10 kV power distribution system,the self-excitation of the AC motor is more common during the transient process of switching the series compensation device.For the line with series compensation device,the fundamental frequency 50 Hz current and low frequency current will appear in the motor stator current and rotor current.The low frequency self-excited current will generate negative electromagnetic torque to offset the torque generated by part of the fundamental frequency current.The average electromagnetic torque of the motor is reduced and below the rated revolution and the motor cannot be used normally,causing a large current oscillation in the system.In this paper,PSCAD-EMTDC software is used to establish two typical radiant structure of 10 kV distribution network with asynchronous motor and series compensation simulation model.The self-excitation phenomena of the motor due to switching of series compensation device caused by such factors as motor capacity,load type and series and compensation capacitance is calculated and studied,the voltage,current and frequency after generation of the self-excitation phenomenon are calculated.The suppression effect of self-excitation of the motor is studied by weakening the capacitance series compensation.It is shown by the result that the self-excitation phenomenon of the motor will generate large over-voltage and over-current.The occurrence of sub-synchronous resonance can be suppressed by way of reducing the compensation degree of the series compensation device,but,on the other hand,the compensation effect of the series compensation device on the system voltage will inevitably be weakened.