Study Of The Three Phase Shunt Active Power Filter

Facing with the more and more serious harmonic pollution in the power grid, which is a consequence of large amount of non-linear loads, power electronic converters and other harmonic sources. Active Power Filter (APF) is bound to be an important development direction of harmonic suppression in the future. Because of its good dynamic performance and automatically adjusting to the harmonic source status, Active power filter has a very broad application prospects in power quality conditioning. With further theoretical research, improvement of power electronic device’s capacity, higher and higher switching frequency and enhancement of digital signal processor’s computing ability, the real-time compensation characteristic of the active power filter will be further improved. In this paper harmonic detection algorithm and control strategy of three-phase three-wire shunt active power filter were discussed as follow:First of all, the problem caused by harmonic current and its suppression measures are briefly introduced. The importance of active power filter in harmonic suppression and power quality improvement is pointed out. The basic principles, topology, harmonic detection method, current tracking control strategy of APF and its applications are briefly introduced. After Analysis, it’s suggested that the three-phase three-wire shunt active filter has a broad application prospects.Secondly, two harmonic detection algorithm based on instantaneous reactive power theory are expounded. The detection results of pq and ip-iq algorithm were compared. Then the detection error using pq method when voltage unbalance is found, meanwhile ip-iq method shown better performance. Further study pointed out that the phase-locked loop is the key to avoid harmonic voltage distortion causing harmonic detection error. Therefore an in-depth study of phase-locked loop is necessary. This paper briefly introduces the several common phase-locked loop (PLL). The typical three-phase PLL based on single synchronous reference frame (SSRF-PLL) is carried on the thorough research, Then it’s found the three-phase voltage distortion and unbalanced leads to phase error. Therefore a new decoupled double synchronous reference frame phase-locked loop (DDSRF-PLL) is introduced to solve the problem and its decoupling strategy is derived from a new method.Then, a three-phase three-wire shunt active power filter mathematical model is established, and its control strategy is given accordingly. Hysteresis current control, SPWM, SVPWM current tracking control strategy are simulated and analyzed. For programming SVPWM is derived in detail. The effects of main circuit parameters on the compensation result are analyzed. Then a main circuit design methods, hardware and software design of control circuits are presented.Finally, according to the design method, an experimental prototype is set up. The harmonic detection algorithm and SVPWM algorithm is realized by C language programming in the TMS320F2812 digital signal processor.