Research on an improved adaptive algorithm applied to active power filters

For the moment, there have been a number of harmonic current detecting methods for active power filters(APF), including the filtration approach by fixed frequency filters, the composition method of the imaginary and the real power based on the instantaneous reactive power theory, adaptive noise canceling method, wavelet technology, and so on. Especially for the adaptive harmonic measuring, since its unique advantages of well bandwidth behaving, simple algorithm, automatically tracking grid fiequency and robustness to circuit parameter variation, it has received significant attention in recent years. The paper provides an improved adaptive algorithm of detecting harmonic currents. It adopts a new variable step size least mean square(LMS) method allowing more flexible control of misadjustment and convergence time without the need to compromise one for the other. Moreover, the algorithm can effectively adjust the step size while maintaining the immunity against harmonic current disturbance. Meanwhile the additional calculation is very little, so the algorithm presented is easy to implement. The simulation results illustrate that the performance of the proposed approach is satisfactory.