Simplified control method for single-phase multilevel active rectifier with current harmonic filtering characteristics

Abstract

The active power filter is an important way to reduce reactive power and harmonic currents from nonlinear loads. A simple control strategy is presented which employs an active rectifier, based on neutral point clamped topology, to work simultaneously as an active power filter to decrease current harmonics. The system power factor is also compensated in the proposed control algorithm. The active rectifier forces the mains current to be sinusoidal and in phase with the mains voltage. A voltage source rectifier, with carrierless hysteresis PWM current control, is used in the inner loop control. A simple PI DC-link voltage controller is adopted in the outer loop control. The control strategy of the adopted active rectifier is based on a look-up table to reduce the cost and required hardware. The proposed scheme can achieve power factor correction, without complicated calculations for harmonic elimination and without a dedicated active power filter. A diode rectifier-fed capacitive load as the nonlinear load is taken on the AC mains to demonstrate the effectiveness of the proposed active rectifier for reactive power and harmonic compensation.