Research On Static Var Generator Based On Backstepping Control

With the increase of power electronic equipment connected to the power grid,the phase difference between grid voltage and current increases,and the problem of threephase imbalance becomes more and more serious.The traditional reactive power compensation technology mainly uses mechanical switching capacitors and synchronous condensers,and this traditional compensation method has the disadvantages of poor dynamic performance,low compensation accuracy,and inability to compensate for three-phase imbalance.In view of the above shortcomings,this thesis takes the Static Var Generator(SVG)as the research object to realize the reactive power compensation of the power grid and balance the three-phase unbalanced current caused by load imbalance,while ensuring that the system maintains good dynamic characteristics and compensation accuracy during operation.The main work and innovations of this thesis are as follows:(1)Firstly,based on the single-phase equivalent model of SVG,the working principle of SVG is explained,the mathematical model of SVG is established,and the sequential compensation strategy of SVG based on dual synchronous coordinate system decoupling(DDSRF)is proposed.This strategy separates the positive and negative sequence current components of the load current through DDSRF,and compensates the positive and negative sequence currents respectively under the rotation coordinates of the two phases.Then,the SVG system model is built in Matlab/Simulink,and the simulation results show that the control algorithm can compensate well for the reactive power and unbalanced currents of the system.(2)The backstep method is applied to the control system of SVG,and a positive and negative dual-sequence synchronous control strategy based on backstep control is proposed.The positive and negative dual-sequence active current reverse step controller and reactive current reverse step controller are designed,and finally the reverse step controller is built in Matlab/Simulink,and the compensation results of the backstep control are compared with the traditional PI control,and the results show that the SVG response speed of the backstep control is fast,the compensation accuracy is higher and the effect is better.(3)After the theoretical research,the hardware circuit design of the main control board,sampling board,LCL filter board,DC side capacitor energy storage board,etc.in the SVG system was carried out,and the hardware-in-the-loop(HIL)simulation test was carried out by RT-LAB equipment.Finally,the software design was completed,and the experimental prototype was built for reactive power compensation and unbalanced current compensation tests.The experimental results show that in practical application,the positive and negative dual-sequence synchronous control strategy based on backstep control has a good effect on compensating for the reactive power of the system and balancing the grid current.