Research On Algorithm Of SVPWM Applied To Fault-tolerant Three-phase Four-switch Active Power Filter

Active Power Filter(APF)can not only extract the power network's harmonic,but also restrain the harmonics and compensate the reactive power.IGBT is an important switch component,which needs to run at high temperature and high frequency,therefore,it has high failure rate.Moreover,once IGBT occur fault,APF has no ways to stabilize continue to operate.Study on allowed mistake APF,on the one hand,it can improve the system's allowed mistake function,when active power filter occur fault,through allowed mistake control then the system stabilize continue to operate,and on the other hand,allowed mistake APF only with two phase bridge arm,it can significantly reduce manufacturing costs in the real application.While the overall power is dramatic less the consumption compare with the six switch system.Therefore,in order to improve the reliability and safety of the operation of APF,the research of fault diagnosis and fault tolerant control strategy technology for APF has great significance.To improve the harmonic compensation ability of fault-tolerant three-phase four-switch APF,a improved SVPWM strategy is proposed.Compared with the traditional SVPWM control method,this method can effectively reduce the error current,at the same time easy to program.Finally the efficiency of this method is verified by simulated analysis.Aiming to the algorithm of conventional space vector PWM is based on different coordinate transformation control algorithm,a unified SVPWM control method based on inductor current is presented.While the traditional SVPWM control needs complex coordinate transformations,the simplified algorithm to change the current as the control target,unified form of the calculation,at the same time the calculation is reduced effectively.The simulation results verify the effectiveness of the proposed algorithm.The main contents are below:(1)To study the fault-tolerant three-phase four-switch topology based on switch redundant topology.While some theoretical analysis of Fault-tolerant active power filter under abc static coordinate system and dq synchronous rotating coordinate system are respectively took into account.The theoretical analysis process is the prerequisite for the selection of parameter calculation and the choice of control strategy.(2)The application of a improved SVPWM strategy is researched.To improve the harmonic compensation ability of fault-tolerant three-phase four-switch APF,a improved SVPWM strategy is proposed.With the traditional SVPWM control method aiming to control the amount of current error rate,this method is different,the method regards the amount of current error as the control target.Firstly calculate the real-time basic voltage vector,and secondly combined with the instruction current and the error of current to calculate best output reference voltage,and reduce the amount of current error to zero.Compared with the traditional SVPWM control method,this method can effectively reduce the error between the output current and the instruction current of three phase four switch active power filter,and improve the harmonic compensation performance,at the same time its programming is easy.Finally the efficiency of this method is tested and verified by simulated analysis.(3)The unified SVPWM for three-phase four-switch Fault-tolerant active power filter is studied.Aiming to the algorithm of conventional space vector PWM for three-phase four-switch fault-tolerant APF is based on the phase A,phase B,phase C fault location selection of different coordinate transformation control algorithm,the calculation process involves a large number of coordinate operations,is not conducive to the fault switching.A unified SVPWM control method for three-phase four-switch fault-tolerant active power filter based on inductor current is presented,and the traditional SVPWM control needs complex coordinate transformations,the simplified algorithm to change the inductor current as the control target,without complicated coordinate transformation calculation,unified form of the calculation,easy to the fault switching.While the simulation analysis is performed,firstly,the design of the fault-tolerant APF system simulation module is completed,and the related system parameters are calculated and solved.Secondly the simulation analysis of the APF fault-tolerant switching algorithm is completed.Finally,the simulation analysis and comparison of the fault-tolerant APF unified SVPWM control based on the inductor current is performed.The simulation results show that this algorithm can effectively reduce the calculation amount of fault-tolerant three-phase four-switch active filter control circuit and improve the accuracy of harmonic compensation.