基于对地参数双端测量及闭环控制的配电网柔性接地有源消弧方法

Flexible-grounding Active Arc-suppression Method for Distribution Network Based on Double-end Measurement of Ground Parameters and Closed-loop Control

针对中性点经消弧线圈接地配电网发生单相接地故障后故障电流难以全部补偿、消弧效果不佳的问题,提出了一种基于对地参数双端测量及闭环控制的有源消弧方法,通过向配电网中性点注入一工频电流来实现故障消弧。所提出的对地参数双端测量法以柔性接地装置的注入变压器为注入端注入一特征频率电流,以消弧线圈内部电压互感器为返回端测量空载电压,实现了配电网对地参数测量。该方法考虑了消弧线圈阻尼电阻,且消除了注入变压器漏阻抗对测量精度的影响,从而消除了传统对地参数测量方法在建模和原理上存在的误差。进一步设计了电流闭环控制方法,由测得的配电网对地参数计算得到注入电流的参考值后,通过比例谐振(proportional resonance,PR)控制器校正注入电流实际值与参考值的差值,再经L型滤波电路后注入配电网中性点,有效抑制故障相电压为0。仿真和实验结果证明了所提方法精度高、响应速度快,可实现接地故障快速可靠消弧,且适用于不同过渡电阻的故障情况。

In consideration of the problem that fault current is difficult to fully compensate and the arc suppression effect is poor after single-phase grounding faults occur in the distribution network with neutral point grounded by the Petersen coil,an active arc-suppression method based on double-end measurement of ground parameters and closed-loop control is proposed,in which fault arc suppression can be realized by injecting a power frequency current into the neutral point of the distribution network.In the double-end measurement method of ground parameters proposed in the paper,the injection transformer of the flexible grounding device is used as the injection end to inject a specific frequency current,and the internal voltage transformer of the Petersen coil is used as the return end to measure the no-load voltage,so as to realize the ground parameter measurement of the distribution network.In this proposed method,the damping resistance of the Petersen coil is considered,and the influence of the leakage impedance of the injection transformer on the measurement accuracy is eliminated,thereby eliminating the errors in the modeling and principle of the traditional ground parameter measurement method.Furthermore,a current closed-loop control method is designed:after the reference value of the injected current is calculated from the measured ground parameters of the distribution network,the proportional resonance(PR)controller is used to correct the difference between the actual value and the reference value of the injected current,and then it is injected into the neutral point of the distribution network by the L-shaped filter circuit,thus the fault phase voltage is effectively suppressed to zero.The simulation and experiment results show that the proposed method has high accuracy and fast response speed,can achieve fast and reliable arc suppression of ground faults,and is suitable for faults with different transition resistances.