Harmonic Analysis And Control Strategy Research Of Three-level SVG

Reactive power compensation is a necessary measure to improve power quality of power system,SVG has the advantage of accurate reactive power compensation,fast dynamic response,low harmonic content etc.,and has become an research focus in the field of power quality.In this paper,three-level SVG harmonic analysis and dual closed-loop control strategy are studied and corresponding new design scheme is proposed.The current ripple is calculated based on the harmonic analysis of three-level SVG output current.Using double Fourier tools,the formula of output current of both two-level and three-level SVG is given.Through the calculation of the output ripple current of these two type of inverters,it is known that the inductance of the inverter side needed for a three-level SVG is only 2/3 of that for a two-level SVG to achieve the same current ripple.Based on the reactive power compensation ability and harmonic suppression requirements of the equipment as well as the characteristics of the output current of the three-level SVG,a design method of three level SVG output filter is proposed.The simulation results show that,the ideal filtering effect can be achieved by using a small inductance value,under the premise of satisfying the reactive power compensation,A design scheme of SVG based on three-level topology is proposed.The two-degree-of-freedom internal model control theory is applied to the SVG dual closed-loop control,which is used to replace the traditional dual closed-loop control.Through calculation and simulation,it is proved that two-degree-of-freedom internal model control method can solve the problem that the traditional method is dependent on the mathematical model and the decoupling parameter setting is complex.The software and hardware design of the system is completed,and the experimental platform is built to test the performance in two cases of load stability and load change.The experimental results show that the design method of the three level structure SVG output filter has good filtering effect when inductance in inverter side is reduced.SVG system with two-degree-of-freedom IMC has higher power factor and better dynamic tracking performance.