Performance analysis of compensation current extraction techniques for 3Ф, 3-wire shunt active power filter under unbalanced supply

Active power filters are effective in mitigating line current harmonics and compensating for the reactive power in the line. Many papers comparing the performance of active power filter extraction algorithms are found in the literature, but there is no explicit mention about the suitability of any particular extraction algorithm under all conditions. Hence this paper is an attempt to compare the performance of direct methods of compensating current extraction algorithms for three-phase active power filters under different conditions of mains supply using Matlab/Simulink^™. Both transient and steady state conditions are considered. The compensating techniques under analysis are: synchronous detection methods, synchronous reference frame method, i_d-i_q method, instantaneous active reactive power theory (p-q theory), modified p-q theory, adaptive noise cancellation, notch filtering and Fourier based sinusoidal subtraction algorithms. Under balanced conditions all the compensating techniques give proper results, but under unbalanced conditions only few of the compensating techniques work satisfactorily. In fact the equal resistance synchronous detection method and Fourier based sinusoidal subtraction algorithms perform better under extreme conditions. With proper implementation, sinusoidal subtraction algorithm performs better under both transient and steady state conditions.