Research On Negative Effects Suppression Method Of AC-contactor Switching

With the development of power industry, the load and electronic devices inpower system become increasingly complex and diverse, users put forward higherrequirements for power quality. Contactor switched capacitor(HVC) has a wide fieldof application in the power quality practical application with many advantagesincluding low cost, large capacity. However surge current and over voltage at theswitched moment greatly threaten the reliable operation of the power system, thusreducing the HVC switching instant negative effects become an urgent problem tobe solved. At the same time, this paper proposed using passive power filter(P PF) tosolve the serious harmonic distoration in the background.Based on the analysis of the transient process when switching contactors, thispaper proposes the synchronous closing strategy. In order to predict the responsetime of the contactor more accurately, this paper describes the switching process ofvacuum contactor, besides, establishes the functional relationship between responsetime and the related factors such as voltage and ambient temperature.The electric power system transient voltage stability criterion based on theoryof stability region is put forward, building the mathematical model according to thesemi-tensor method. Meanwhile this paper analyzes the relationship betweentransient voltage stability and the fault clearing time, what’s more, the systemstability is presented in this paper when HVC and PPF are switched to the system.In order to suppressing the HVC negative effects such as inrush current andvoltage flicker, the topology of HVC and PPF are designed in this paper. Thereactive power compensation mode is described when the system work in differentcombinations. In order to avoiding the over compensation and parallel resonance,the system model are build in the conditon of fundamental current and harmoniccurrent, respectively,Design the HVC zero switching control platform based on ARM, analyzing thevariation of current and voltage of HVC when using synchronous closing strateriesand asynchronous closing control strategy respectively, according to theexperimental result, when using the synchronous closing control algorithm, thecontactor can be colsed at the time of voltage crossing zero and opened at the timeof currrent crossing zero. Simulation and experimental results show that thesynchronous closing strategy can effectively avoid the HVC switching negativeeffect.