A three-phase voltage-type PWM rectifier with the function of an active power filter

In recent years, harmonic pollution in electrical power systems due to nonlinear loads such as AC/DC power converters has become a serious problem. To eliminate or reduce harmonics in power systems, a number of methods have been developed and put into practice. Active power filters and PWM rectifiers are two typical examples of these methods. The active power filter and PWM rectifier have basically the same circuit configuration and can operate based on the same control principle. Therefore, one can design a power converter capable of both the active filter operation and PWM rectifier operation at the same time. Such a converter operates as a PWM rectifier to supply DC power to its own load and, at the same time, operates as an active filter to supply to the AC line a compensating current equal to the harmonic current produced by the nonlinear load connected to the same AC line. Here, a three-phase voltage-type PWM rectifier with the function of an active power filter is investigated.