Research On Current Detection Method Of Capacitor Split Three-phase Four-wire DSTATCOM

With the fast development of modern industrial production in China,various kinds of electrical equipment are put into power system,which leads to a series of power quality problems such as harmonics,reactive power and three-phase unbalance in three-phase four-wire distribution network,which seriously endangers the safe operation of power system.Distribution network static synchronous compensator(DSTATCOM)can compensate harmonics,reactive power and three-phase unbalance dynamically.It plays a very important role in the stable operation of three-phase four-wire distribution network.Therefore,it is of great significance to study the application of DSTATCOM in three-phase four-wire system.In this paper,split-capacitor-type three-phase four-wire DSTATCOM is taken as the research object,and its compensation current detection method is mainly analyzed.Firstly,three main circuit topologies of three-phase four-wire system are analyzed and compared,and split-capacitor-type three-phase four-wire system DSTATCOM is chosen as the main circuit topology in this paper.The mathematical model of split-capacitor-type three-phase four-wire DSTATCOM is established by using switching function method in abc static coordinate system,and the mathematical model of main circuit in dqO rotating coordinate system is obtained by coordinate transformation.Then,the common compensation current detection methods are introduced,and the p-q-0 current detection method,ip-iq-iO current detection method and zero sequence current separation ip-iq current detection method based on instantaneous reactive power theory are analyzed.Aiming at the shortcomings of current detection method based on instantaneous reactive power theory,a current detection method without phase-locked loop for three-phase four-wire DSTATCOM under unbalanced load is proposed.In view of the limited compensation capacity of DSTATCOM,a selective current compensation detection method is introduced,which enables DSTATCOM to selectively compensate the harmonic,reactive and unbalanced components of the load current.The simulation results show the feasibility of the proposed current detection method.Finally,on the basis of software and hardware design,a three-phase four-wire DSTATCOM experimental platform is built and experimental verification was carried out.The experimental results are basically consistent with the simulation results,which shows the effectiveness of the proposed current detection method and the rationality of the experimental platform design.