Research On A New Flexible Grounding Compensation And Line Selection Device

In the power system, depending on the difference of the neutral grounding mode,the grids can be divided into large current grounding systems and small ones. InChina, small current grounding systems generally adopt neutral grounding via arcsuppression coil. Because of the superiority of the resonant grounding, many othercountries of the world also adopt neutral grounding via arc suppression coil inlow-voltage grid.The arc compensation devices proposed by the scholars now have been analyzedand compared in this paper, it is find that the existing arc suppression coils were madeaccording to the Petersen coil principle. At the instant of single-phase ground fault,because of the approximate resonance status between arc suppression coil andcapacitor resonant, ground instantaneous over current often happened. In this paper,based on the equivalent model of resonance grounding system with single-phase toground fault, it is analyzed that the fundamental mechanism of arc suppression coilgrounding compensation is that the Petersen coil will produce a current of oppositephase to ground capacitance current to compensate it. According to this trail, it couldbe thought that if an inverter device which could issued an inductive current wasinstalled between the neutral point and the ground, then this device could replace theexisting Petersen coil.This new flexible grounding compensation device proposed in this paper is toregard the inverter of the neutral point as a current source controlled by zero sequencevoltage, then the inverter could produce a current which lagged the neutral pointvoltage of90°to compensate the grounding capacitance current. In this paper, thefeasibility of the new flexible grounding compensation device has been test andverified in Matlab/Simulink.The new flexible grounding compensation device proposed in this paper isdifferent from the previous Petersen coil, so it needs a new tuning method which ismore suitable for this device. On the basis of analyzing the existing tuning methodproposed, a new method is proposed to measure the capacitive and impedance currentof resonance grounding power networks based on the phase offset of thezero-sequence voltage. The method can be used with the new arc proposedcompensation device, and the adaptability and flexibility of the tuning replied to thedifferent systems has been increased. Then, the basic principles and advantages and disadvantages of some of theexisting line selection methods has been introduced in this paper. An Improvedresidual proposed incremental method has been proposed and applied in the newcompensation device. And the relevant simulation with this method applied with thenew compensation device has been carried out.Finally, the software and hardware systems of the new flexible groundingcompensation device have been designed preliminarily, and it laid the foundation forthe development and operation in actual of the device and in the future.Compensation experiments have been carried out on a simulation system, and theresult seems good.