The Study On Modularized Shunt Active Power Filter

Active power filter(APF) has favorable dynamic response and compensating characteristics. Because of its high technique content and high performance, APF must substitute passive filter(PF) and become the development trend of harmonic elimination in power system. Shunt APF is the main kind of APF, which has extensive users and the most promising of development. This paper describes shunt APF's principle, harmonic detection, compensating current control and total circuit design.According to APF's working characteristics, a simple applied and real-time harmonic detecting method is presented in this paper, which is evolved from traditional analysis of Fourier transform. After digital disperse, the real-time measurement can be realized conveniently by programming approach. The mode of compensating current control determine the compensating effect. This paper introduces delay-cycle controlled PWM method for its high current tracking speed. The effect of control parameters on compensating results and the requirements to power electronic devices are derived in theory.At present, the capacity of all-controlled power electronic devices is small, so the design capacity of APF is limited. This paper bring forward the modularized design method to extending APF's design capacity, in short, which emploies a main controller to dominate several compensating cells by optical communication. Changing the number of cells can adjust the capacity of APF.In this paper, simulation software of EMTDC/PSCAD is used to examine the design method. The result show that this design has expectable compensating effect, the action of control parameters is in agreement with the theoretical results.