The Study Of Optimal Tuning Method In Resonant Grounded System Based On Immune Algorithm

The neutral point with arc suppression coil grounding(also called resonant grounding)has outstanding advantages when dealing with the single-phase earthed fault,which greatly improved the running stability of the resonant grounding system.So it's widely used in urban power distribution system.However,advantages of this grounding method are based on accurate tuning of arc suppression coil.Disadvantages such as high displacement voltage of neutral point and over-voltage inside the resonant grounding system will arise if improper tuning happened.Therefore,study of tuning method and the tuning device in the resonant grounding system have important theoretical significance and engineering value.The running principle of the resonant grounding system in this paper was deeply analyzed,as well as two aspects of fault characteristics about transient and steady state when the single-phase earth fault occurred.Besides,the existing tuning methods and tuning devices of resonant grounding system were also clarified,and the shortages of the existing tuning technology were pointed out as well.On this basis,this paper also analyzed several typical research methods about the improved arc suppression coil tuning technology.The optimization of tuning method of the resonant grounding system,which based on immune algorithm,was proposed in this paper.This method fully considered the factors that influence the tuning of arc suppression coil in resonant grounding system.If the best comprehensive performance of the resonant grounding system has been ensured,out-of-resonance degree that describe the tuning state of the arc suppression coil will be the optimization goal,and the optimum out-of-resonance degree can help to calculate the optimum inductance current which can achieve the goal of tuning optimization.The tuning optimization mathematical model of the resonant grounding system was established in this paper.In order to obtain the comprehensive optimization goal of the three party including the displacement voltage of neutral point,the grounding residual current and the rising speed of recovery voltage of gap arc at the beginning,this model analyzed the effect of damp rate and out-of-resonance degree in the resonant grounding system on the tuning of arc suppression coil.On the other hand,the optimization objective function that the overall safety of the resonant grounding system was also obtained on the basis of analyzing the weight of three tuning parameters in the tuning process.The tuning optimization operator was designed according to the optimization model of out-of-resonance degree,and the excellent convergence characteristic of immune algorithm is proved by simulation with Matlab.With the analysis of examples,the optimization process was completed by using immune algorithm within the limits of out-of-resonance degree.In conclusion,the example proved that tuning optimization method based on immune algorithm has better optimization results and improved the security and reliability of the resonant grounding system.