Research On Three-Phase Shunt Active Power Filter Based On Digital Signal Processor

With the vast use of electrical and electronic elements and the customer's incessant demand for electrical power of higher quality, all kinds of electrical and electronic devices for harmonics elimination come into use. Among of them, the three-phase shunt active power filter (APF) is most representative. Considering the reality of harmonics pollution which widely exists among industrial users, three-phase shunt APF is studied in the paper. From the angle of engineering, some key problems in harmonics detecting and compensating parts are studied, which accumulates much experience for the engineering use of APF.Firstly, the necessity of harmonics elimination is expatiated, research status, categorization, basic principle and popular control strategy of APF are briefly analysed , research points of the paper are also given.Through detailed theory and mathematic analysis, combined with digital simulation, p-q and ip-iq harmonics detecting methods based on instantaneous reactive power are studied. Based on compare, the ip-iq harmonics detecting method is used as the final scheme.The digital low-pass filter is crucial to harmonics detection. Through accurate analysis and systemic compare, parameters and type of the low-pass filter are given. Considering possible unsteadiness of the filter system due to the limited word length of DSP TMS320LF2407A, a new method by extending effectual word length is put forward. Software based on assemble language is finished and debugged successfully under the DSP platform of CCS2.0. Experimental results validate system design above.After systemic compare of the control strategy for current compensation, the method of hysteresis compare is used as the final solution to track harmonics. The problem of switching noise is analyzed in detail and analog filter between APF and power system is designed according to the equivalent circuit of compensation part. Parameters are verified in simulation environment and the scheme of optimizing parameters are put forward at the same time.Finally, with the chosen detecting and compensating scheme, design of the whole APF system is finished and the corresponding flow chart is presented, introduction in detail to main parts is also given. The simulation model based on Matlab/simulink is built up. Simulation results under different system environments and load conditions validate system's static and dynamic performance.