Delayless harmonic detection based on DSP with high-accuracy for active power filter

This paper presents a delayless harmonic detection system based on DSP with high-accuracy for active power filter. Modified structure adopting new signal-flow is introduced, which can effectively integrate analog control and digital control. Phase-shift compensating strategy is introduced into the synchronous-reference-frame based detection algorithm to overcome time-delay induced by digital control. Some design issues such as evaluation of time delay and digital phase shift is discussed. Furthermore, to guarantee satisfactory detecting performance, low sampling rate based low pass filter design helps to realize accurate fundamental current extraction overcoming the limitation of certain DSP resource. Experimental results verify the excellent performance of the presented harmonic detection system.