POWER FACTOR IMPROVEMENT AND HARMONIC CURRENT REDUCTION IN DUAL FEEDBACK PWM CONTROLLED AC/DC DRIVES.

The electrical power industry has grown rapidly and loads are changing from simple, non-electronic loads to electronic ones. These electronic loads draw a non-sinusoidal current even when the supply voltage is perfectly sinusoidal. In this paper PWM controller with dual feedback loop with simple single-stage single-switch input-current shaping circuit was designed, simulated and tested for AC/DC drives which generates input current harmonics due to its non-linear characteristics. A sinusoidal input current with nearly unity distortion factor was achieved through current harmonics reduction by using PWM boost regulator. The circuit utilizes the charging and discharging increments of boost inductor current to shape a sinusoidal input current. Inductor current was controlled by means of PWM controller. The controller accepts two feedback signals, the first is the inductor current and the other is the output voltage of the AC/DC drives. The simulation results of fast Fourier transform (FFT) show the great reduction in current harmonic which in turns tends to a great improvement in power factor and the sinusoidal shape of input current and hence overall performance of AC/DC drives