Four-Wire Current Source Active Power Filter with an Open-Loop Current Control

Although three-phase three-wire shunt active power filters have been implemented using both voltage and current source technology, four-wire shunt active power filters are mainly voltage source active power filters. In fact, only minimum research on four-wire current source active power filters has been accomplished over the years. This paper studies the performance of a four-wire shunt current source active power filter topology. The main circuit of the proposed topology consists of a four-leg current source PWM converter bridge with an LC-type supply filter. The ac current control of the active power filter is implemented in an open-loop manner using only the feedforward connection of the load currents. In addition, the control system includes prediction based current reference generation, computational control delay compensation and current oscillation compensation. The performance of the proposed system is tested experimentally using a microcontroller controlled four-wire current source active power filter prototype.