Analysis and evaluation of different modulation techniques for active power filters

The effectiveness of an active power filter depends basically on three characteristics: (a) the design characteristics of the PWM modulator, (b) the method implemented to generate the reference template and (c) the modulation method used. For the last characteristic there are many methods, most of them based on PWR strategies. In this paper, three of these methods, whose characteristics are their simplicity, are analyzed: periodical sampling control, hysteresis band control, and triangular carrier control. These three methods have been tested with different waveform templates: sinusoidal, quasi-square and rectifier compensation current. The paper shows that, depending on the type of current the active filter has to follow, one strategy may be better than the others. The analysis is based on using the same switching frequency and the results are compared through a THD method which takes into account the particular shape of the waveform template. Simulations and experimental results are presented in the paper.<>