An improved harmonic detection based on lead compensation for active power filter

Active power filter (APF) with digital control is widely used to solve harmonic problems. But inherent delay time introduced by digital control significantly affects the performance of APF. Here, we introduce an improved harmonic detection method by using phase-shifting. In order to shorten the computation time of harmonics reference, we use the data calculated in the last sample period. So the delay time is shortened, and the performance of APF is improved. The whole algorithm is based on generalized instantaneous reactive power theory. This method is easy to realize and useful for industrial application. A 50 kVA three-phase four-wire shunt active power filter is implemented. The controllers with two types of TI digital signal processors (TMS320LF240 and TMS320F2812) are compared. Experiment result shows good performance employing the new algorithm for APF.