Novel PWM line conditioner with fast output voltage control

Abstract

A novel pulse-width modulated (PWM) line conditioner with fast output voltage control is proposed. The line conditioner is made up of a PWM AC chopper and a transformer for series voltage compensation. In the PWM AC chopper, a proper switching operation for solving the commutation problem is achieved. Power semiconductor modules which are commercially available can be used in this circuit and regenerative DC snubbers are attached directly to power semiconductor modules to absorb the energy stored in line stray inductance. These regenerative DC snubbers have a very simple structure consisting of a capacitor only with no discharging resistors or complicated regenerative circuit for snubber energy. Therefore the proposed AC chopper gives high efficiency and high reliability. The output voltage of the line conditioner is controlled using rapid sensing of the output voltage. The optimal gains of the controller giving an output with small overshoot and adequate damping are designed using the time-weighted quadratic performance index. It is also shown using simulation and experimental results that the proposed line conditioner gives good dynamic and steady state performances with high quality output voltage.