Compensating Characteristics of a Series-Shunt Active Power Filter Considering Unbalanced Source Voltage and Unbalanced Load

Recently, the suppression of the harmonic component in the electric power system has become an important problem. In this paper, we analyze compensating characteristics of a series-shunt active power filter by simulation and experiment when source voltage or load current becomes unbalanced. The harmonic and unbalanced voltages are detected and compensated in a series active filter using dq0 transformation. The harmonic and unbalanced currents are detected and compensated in a shunt active filter using pq-theory. The results of analysis show that the THD of the compensated voltage is 1.0% by simulation and 8.3% by experiment. The THD of the compensated current is 3.0% by simulation and 7.2% by experiment. It is shown that the series-shunt active filter can compensate the voltage and the current simultaneously and it has excellent compensating characteristics even when unbalanced components occur in the electric power system.