Active Power Filter with Indirect Control for Line-Frequency Controlled Rectifiers

Line-frequency controlled rectifiers have two major disadvantages: variable displacement power factor and high harmonic current fed to the power supply. If the power converter is large, e.g. for rolling mills drives, it is necessary to use a local reactive-power and harmonics compensation The control of shunt active power filters, APF, using PWM inverters, consists in generating a reference by separating, using different methods, the harmonics to be eliminated. The methods used are time-consuming and need dedicated control and signal processing equipments. To avoid these setbacks a new method is proposed in the paper. The active power filter is a current PWM rectifier with voltage output and a capacitor on the DC side. The PWM rectifier is controlled so that the sum of its current and the non-linear load’s current is a sinusoid in phase with network voltage. The control block schema as well as simulation results are presented.