A family of control methods for parallel active power filters based on current detection

This paper discusses a systematic method to analyze and design the control of parallel active power filter (PAPF). The discussion begins with a universal two-port representation of power stage of PAPF. With the power stage represented by this two-port block, a general control diagram based on current detection is proposed. Different control schemes can be obtained from this general control diagram with different gains of each detected current. For simplicity, this paper discusses four kinds of gains, including zero pass, full pass, high-frequency pass and low-frequency pass. A systematic procedure is then proposed to generate all possible 64 possible control schemes, and the criteria are derived to verify the validity of each control scheme. According to these criteria, there are 4 valid ones among the 64 possible schemes. Only one of these 4 control schemes has been known previously and used in practice. The other three new practical control schemes are further analyzed in detail. Further more, the authors found that these valid control schemes are not independent, and their internal relations are revealed. This conclusion is really helpful for electrical engineers to analyze and design the control of APF. The derived new control schemes are verified by both time-domain computer simulations and experimental tests on hardware prototypes.