| With the rapid development of the power electronics industry,non-linear loads are used in different fields rapidly,which makes a large of harmonic problems in the power grid.In addition,the sensitive devices must work with higher power quality,which makes it urgent to improve power quality.The back-to-back converter in the traditional unified power quality conditioner(UPQC)has many switching devices and complicated structure.By replacing the back-to-back converter in the UPQC with a nine-switch converter,the amount of switching devices can be reduced by 25%,and it has the advantages of small size and low loss.According to the characteristics of UPQC based on nine-switch converter,this paper has carried out a series of researches on modulation methods,mathematical model and control method,which are as follows:At first,a new mathematical model for the UPQC based on nine-switch converter can be stablished by using the switching function and Clark transform.;secondly,a new space vector modulation method is proposed based on the relationship of voltage vectors between the nine-switch converter and the traditional six-switch converter,and the modulation indices for two AC terminals is analyzed in detail;thirdly,the control method based on the nine-switch converter UPQC is given according to the instantaneous power theory,and the control principle is analyzed in detail;finally,the simulation model of the whole system is built by MATLAB/Simulink and simulated in different cases to verify the control method.The simulation results show that the proposed control method has good compensation effect and verifies the feasibility and effectiveness of the control method.The research of the UPQC based on nine-switch converter in this paper shows that can realize the comprehensive control of power quality,which provides the theoretical basis and engineering application basis for the further application of the nine-switch converter and the comprehensive control of power quality. |
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