Study On Detecting Methords For Harmonic And Reactive Current In Active Power Filter

The wide use of power electronic equipment makes harmonic problem deteriorated increasingly, and harmonic becomes the primary factor influencing power quality. Active power filter is considered as an effective method to restrict harmonic. Research and application are widely studied. An accurate and real-time detecting approach is critical for APF to accurately compensate harmonic currents. This paper mainly research on harmonic current detecting methords.Baseed on the existing detection methods of harmonic currents, a novel harmonic current detecting method used for active power filter (APF) was presented, by this method in the thesis, the amplitude of fundamental positive-sequence active component of load current (I_1p) is calculated according as instantaneous real power, and then multiply by the unit amplitude supply voltage to obtain the compensation current components.Another novel harmonic current detecting method aimed at the harmonic currents of Resistance-indutance Load Rectification circuit was presented. In this method, the DC side current of rectification circuit is demanded to detect firstly, then the fundamental positive-sequence active component of load current (i_1p) is calculated by a simple calculation process, the compensation current components would be obtained.Moreover, shunt active power filter's control strategy is analyzed in detail, a simulation model for APF based on PSIM was built: (1) Simulation study was carried out at different load characteristics and fluctuating load condition. Simulation results show that this method can quickly and accurately detect the harmonic and reactive components of the load current; (2) In order to analysis correlative factors effecting APF compensation effectiveness, much simulation study are achieved on parameters including AC side inductance,DC side voltage, compensation capability and switch-frequency of APF main circuit., and discovering some important conclusion.The thesis built a shunt active power filter system's hardware and software design with DSP. Hardware and software's structure and function are described in detail. And experiment results verify validity and effectiveness of the current detection method.