Power factor improvement in rectifier circuit — A simulation study

Switching power supply in computers and motor drive systems operate by rectifying the input AC line voltage using diodes and filtering it with large electrolytic capacitors. This results in distortion of input current waveform which is highly peaky in nature. The reduction of input current harmonics and improved power factor operation are important from the energy saving point of view and also to satisfy the harmonic standards. Generally, passive and active filters are used to improve the power factor of diode rectifiers. Another solution is to use high switching frequency devices instead of diodes. Such rectifier circuit is known as pulse width modulated rectifier. This paper analyses and compares the performance of a single phase pulse width modulated rectifier with commonly used diode rectifier. It is observed that both harmonic reduction and easy power control can be achieved in the case of pulse width modulated rectifier without any additional filters. This paper proposes a new and a simple method of generation of reference signal for generating pulses using sine triangular pulse width modulation technique for controlling the switches of the rectifier circuit. A MATLAB simulation is carried out for a 110V, 1kW rectifier for verification of the control technique and satisfactory results are obtained.