Research On The Hybrid Compensation Model Of Unbalanced Three-phase Load In Low Voltage Distribution Network Based On SVC+SVG

More and more non-linear and unbalanced loads have appeared in the low-voltage distribution network because of the rapid development of science and technology,and the three-phase load imbalance has become more and more serious,which seriously affects the power quality of the power grid.Therefore,the management of three-phase imbalance has become an urgent problem to be solved.The Static Var Generator(SVG)has the advantages of high compensation accuracy and fast response speed.In the case of three-phase active imbalance,the active power can also be adjusted.However,if SVG is used for large-capacity compensation,the cost of SVG is very expensive due to the limited technical level at present.The Thyristor switched capacitor’s structure is simple,low in cost,easy to control,and has no harmonics.It is widely used in the field of reactive power compensation.However,due to its own technical characteristics,there are still some shortcomings such as slow response speed and poor compensation accuracy.Thyristor switched capacitor(TSC)and static var generator(SVG)have complementary advantages in terms of compensation and cost.Therefore,this paper takes the SVC+SVG hybrid compensation method as the research object.Firstly,the working principle and topological structure of TSC and SVG are introduced,and establishing the related mathematical model.The split-capacitance three-bridge SVG is used to adjust the three-phase load imbalance of the low-voltage distribution network.Secondly,the control strategy of the hybrid compensation is determined.By comparing the two capacitor grouping methods and various reactive power compensation basic control methods,TSC selects a control strategy that avoids switching oscillation and can realize a stepwise capacity change of the capacitor bank.In the SVG module,several detection methods for time domain detection are selected,and the current detection method with small calculation and high real-time performance is selected.Based on this,the traditional low-pass filter is improved,and the improved current detection is obtained through simulation verification.The superiority of the method.In the control strategy of SVG,the tracking control of DC side voltage and compensation current is mainly studied,and simplified 3D-SVPWM is adopted.Under the premise of ensuring good effect,the calculation amount of traditional modulation method is greatly reduced.Finally,using the simulation function of MATLAB,the integrated simulation model of hybrid compensation is established,including TSC control module,SVG current detection module,current tracking and modulation module.The simulation results are analyzed and the rationality of the design of the hybrid compensation system is proved.