感应电动机稳定性判别与切负荷控制

Stability Discrimination and Load Shedding Control of the Induction Motor

感应电动机负荷的动态特性对暂态电压稳定性和负荷稳定性有着重要影响。当系统发生严重故障或扰动时,可能造成感应电动机堵转,导致负荷失稳及电压崩溃。对感应电动机机械暂态模型进行简化,并利用戴维南等值电路对感应电动机负荷的外部网络进行等效,从而推导出感应电动机临界稳定滑差的实时计算方法。另外,采用切负荷控制来防止感应电动机失稳,利用不平衡转矩来计算切负荷比例。IEEE 3节点系统的仿真结果说明,使用所提出方法得到的扰动后感应电动机稳定性判别结果与仿真结果一致,该方法计算得到的切负荷量大于保证感应电动机稳定性的最小切负荷量,能够有效保障负荷稳定性和电压稳定性。

The dynamic characteristics of induction motor load have significant influence on both load stability and transient voltage stability. The induction motor may be locked during severe faults or disturbances, thus resulting in load instability and voltage collapse. This paper simplifies the mechanical transient model of the induction motor and uses Thevenin＇s equivalent circuit to simulate the external network of the induction motor, thus proposing a real-time method to calculate the critical slip of the induction motor. Furthermore, this paper employs load shedding control to avoid instabilities of the induction motor, and the load shedding proportion is calculated based on the mismatch torque. Results of simulations on IEEE 3-bus system have shown that the result of stability discrimination of the induction motor after disturbances is approximate to the simulated one and the calculated load shedding amount is greater than the minimum load shedding amount which is to guarantee stability of the induction motor, and this can effectively ensure load stability and voltage stability.