Application Of Three-phase Four-leg SVG In Three-phase Unbalance Regulation Of Low-voltage Distribution Network

With the rapid development of distributed power sources,energy storage devices,new energy vehicles,and the increase of single-phase loads on the user side,the three-phase imbalance problem in the low-voltage distribution network has become increasingly serious,which not only affects the safe operation of electrical equipment,but also increases the power loss on the line.For this reason,this paper designs a three-phase four-arm SVG system to solve this problem.This article first introduces the working principle of SVG,and compares and analyzes three common three-phase four-wire SVG main circuit topologies,and chooses three-phase four-leg topology with simple structure and good economy.Then three kinds of reactive current detection methods suitable for three-phase four-arm SVG are introduced,namely p-q-p0 detection method,ip-iq-i0 detection method,and id-iq-i0 detection method,An improved zero-sequence current separation method is designed.This method uses a moving average filter instead of a traditional low-pass filter,which can quickly and accurately detect the compensation current signal and is easy to program on DSP.Then the control strategy of the three-phase four-arm SVG system is studied,and the compensation current is modulated by 3D-SVPWM,and the space vector modulation in the ab-c coordinate system and the α-β-γ coordinate system is compared and analyzed,and the calculation amount is selected Fewer and easier to digitize the threedimensional space vector modulation mode in the a-b-c coordinate system.Finally,MATLAB/Simulink is used to build a three-phase four-arm SVG system simulation model,and the simulation analysis is performed under three different load conditions to verify that the system has the functions of reactive power compensation and three-phase imbalance control.And design the hardware circuit and software program of the system.