Study On Fault-tolerant Three-phase Four-switch Active Power Filter

With the rapid development of modern technology,the power electronic devices have been widely applied,and the generated harmonic currents cause great pollution to the power grid.The demand for harmonic suppression has promoted the emergence and rapid development of active power filters.Switching devices in active power filter are prone to be damaged in long-term operation,resulting in system operation errors or even paralysis.Therefore,the research on fault diagnosis and fault-tolerant control has attracted much attention.Based on the establishment of the purpose and significance of the research of the active power filter,the important significance of fault-tolerant operation of active power filter is discussed by consulting a lot of literature at home and abroad.At the same time,the research status of fault diagnosis method and fault-tolerant operation scheme are summarized.Based on the study of fault-tolerant three-phase four-switch active power filter’s detection method,fault diagnosis method and control strategy,the design scheme of fault-tolerant active power filter based on dq detection,current vector trajectory slope method and fuzzy adaptive PR control is determined.In order to solve the problem of neutral point potential offset in DC bus,a compensation scheme of voltage difference feed-forward is proposed.According to the key element parameters calculated by the theory,the joint simulation of PSCAD/EMTDC and MATLAB software is carried out.The overall model of fault-tolerant three-phase four-switch active power filter is built,and the compensation performance of the harmonic when APF runs before the fault occurs,runs after the fault occurs and runs in topology reconfiguration state after the fault occurs are analyzed separately.The compensation effect of the fault-tolerant three-phase four-switch active power filter with the traditional PR control and the fuzzy adaptive PR control is compared and analyzed.The simulation results show that the fault-tolerant three-phase four-switch active power filter system designed in this paper has good harmonic compensation effect before and after the topology reconstruction operation,and the harmonic distortion rate is significantly reduced.On the basis of theoretical analysis and simulation verification,the hardware circuit and software program of the system are designed,and the experimental platform is set up.The compensation performance of fault-tolerant three-phase four-switch active power filter is further studied.The experimental results show that the system designed in this paper can effectively compensate the harmonics before and after the fault,and proves the correctness of the design.