Research On Balancing Compensation Method Of Accessing To Grid For Charging Pile

Charging Pile mainly adopts the DC and AC Charging Pile,the former use three-phase AC power supply,the latter use single-phase power supply,so Charging Station accesses to three-phase four-wire grid.The random and disorderly charging of different type of electric vehicle will consume larger reactive power,and make the power three-phase imbalance and middle-line zero sequence current overload,therefore introducing the static reactive power generator for distribution network(D-STATCOM)realizes optimal balancing compensation.Firstly,the background and significance of the study was analyzed,and analyze and compare the reactive power compensation device,determine to introduce D-STATCOM to achieve balance compensation.Balance power grid system with Charging Pile accessing are introduced,analyze D-STATCOM topology structure on the basis of compensation principle,select three-phase four-bridge arm D-STATCOM to achieve balanced compensation.Then,in view of the load specialty of Charging Pile,analyze reactive current test and compensation control strategy of D-STATCOM.Due to the load current contains negative sequence and zero sequence components,the ip-iq test based on instantaneous reactive power theory can't accurately detecting reactive current,so must improve it.First isolate zero sequence component from the load current,and use signal time delay method separate the positive and negative sequence component,then introduce single synchronous phase-locked loop based on positive sequence of grid voltage reactive component to improve the traditional PLL.The positive and negative sequence synchronization compensation strategy based on feedforward decoupling is used to control three sets of bridge arm to realize reactive power and unbalanced compensation and hysteresis comparison strategy is used to control a set of bridge arm to realize zero sequence current compensation of neutral line.Finally build and debug model simulation for overall system,use semi-physical simulation system make hardware in loop test for improving the confidence level of the system.Adopt three-phase four-bridge arm D-STATCOM to realize balanced compensation.Improve the i_p-i_q test can accurately detect the reactive current of the random and disordered charging behavior of Charging Pile,and make control strategy implement the rapid compensation of unbalance,reactive current and zero sequence,improve the grid that has Charging Pile power quality.