Continuous time and discrete mathematic model of active power filter(APF) are derived, and then the whole control structure is introduced. A deep analysis of traditional deadbeat control is done. It is found that traditional deadbeat control cannot achieve the real deadbeat control and its control accuracy is not high if the delay of AD sampling and DSP digital calculation are considered. In order to solve this issue, an improved deadbeat control is presented so that two poles of closed-loop transfer functi...