A 3-phase series active power filter with compensate voltage drop and voltage unbalance

In this paper, a three-phase series active power filter to compensate harmonic current, voltage drop and unbalanced voltage in power distribution systems is studied. The main circuit of the APF consists of a voltage source inverter with space vector modulation and a high pass filter connected in parallel to the power system. The APF is connected in series to the transmission line through a single-phase transformer with a turns ratio of 1:1. Here, the load is a six-pulse thyristor rectifier. The phase angle detected in order to generate the reference voltage at the load terminal is synchronized with the positive sequence component of the unbalanced source by using symmetrical component transformation. The proposed system has harmonic isolation between the source and load, voltage regulation and unbalance compensation. To verify the validity of the proposed compensating system, both computer simulations and experiments are carried out.