Control of a new active power filter using 3-D vector control

The growth in distorting loads has given an interest in the design of three-wire active power filters, switching circuits which can be installed in an installation and generate harmonic currents to neutralize the loads´ distorting current. With no neutral, the currents have two degrees of freedom and can be represented by two-dimensional (2-D) vectors. This approach leads to a control strategy which can compensate for balanced three-phase distorting loads. However, there has been a growth of single-phase distorting loads which give large neutral currents at triplen frequencies and which cannot be dealt with by the three-wire active power filter control. This paper reports the development of a three-dimensional (3-D) vector treatment of unbalanced three-phase circuits which can be used instead for the development of a control strategy. Simulation studies show that the control is effective, not only for the removal of harmonics, but also for the compensation of fundamental unbalance currents