Fast Tripping Theory Used In Multi-Channel Power Crid

As the last defense line of power system,out-of-step separation is an important method to avoid failures caused by the expansion of large-scale blackout.Nowadays,out-of-step separation criterion is still based on the local data to get the electrical information of out-of-step channel,which have the low speed of out-of-step separation and have low accuracy to determine oscillation center.While fast out-of-step separation criterion can overcome the disadvantages above and have good application prospects.Firstly,this paper analyzes the variation of electrical data in out-of-step channel and fast out-of-step separation criterion after the power system out-of-step,which show that fast out-of-step separation criterion is faster and better positioning accurate than other out-of-step separation criterion.At the same time,some problems are proposed when fast out-of-step separation criterion is used in multi-channel power grid.Secondly,an improved fast out-of-step separation criterion is proposed after analyzing and reasoning the problems of fast out-of-step separation criterion.Improved fast out-of-step separation criterion retains the original advantages:the ability to judge the oscillation state of out-of-step channel in the first period of out-of-step oscillation and accurately capture the oscillation center.At the same time,some flaws that are caused by the original fast out-of-step separation criterion used in multi-channel power grid are solved.First,the problem of waste equipment is solved by the improvement that the criterion can effectively judge oscillation at either end by using the change rate of apparent impedance angle.Second,the stability function that is based on the transient potential energy function at the period of out-of-step oscillation is used in fast out-of-step separation criterion to decide the order of separation channel,which can avoid the circumstance that oscillation cannot be eliminated because of the change of out-of-step section.Finally,the improved fast out-of-step separation criterion is proved by simulation with actual power grid model in various regions,which proves the correctness,effectiveness and superiority of the improved fast out-of-step separation criterion and separation order based on stability function.