Harmonic elimination; Reactive power compensation; Active power filter; Load balancing
In this paper, a new control scheme of a three-phase active power filter (APF) is proposed to eliminate harmonics, to
compensate reactive power and neutral currents and to remedy system unbalance, in a three-phase four-wire electric power
distribution system, with unbalanced non-linear loads. The APF is realized using three single phase IGBT based PWM-VSI
bridges with a common dc bus capacitor. A hysteresis rule based carrierless PWM current controller is used to derive gating
signals for the IGBTs. Three-phase balanced reference supply currents are estimated using load currents, dc bus voltage and
supply voltages. The reference currents of the APF are derived by taking the difference of corresponding reference supply current and load current. The APF forces the compensating currents to conform to the desired reference currents. The APF is found effective to compensate reactive power and neutral current while eliminating harmonics with load balancing.