A single-phase PWM current source type converter coupled with an ac chopper

A current source type converter can easily generate a sinusoidal current on the ac side by employing a PWM strategy. In the converter system for a single-phase supply, however, the de current pulsates because the de output voltage of the converter contains an ac component with twice the ac supply frequency. The de current pulsations cause the ac current waveform to be distorted. Although the use of a de reactor with large inductance reduces the de current pulsations, the size and the weight of converter equipment including a de reactor is large. Two-phase rectification using two full-bridge converters and a converter system with an ac chopper circuit has been proposed for elimination of the de pulsations. In these converters, the number of switching devices comprising the circuit will unavoidably increase. To solve this problem, we propose a novel single-phase current source type converter coupled with an ac chopper circuit and the PWM method. In this circuit, two switching devices in the main bridge are used to form an ac chopper bridge with two added devices and a capacitor This paper gives the experimental and theoretical waveforms and the steady-state characteristics. The results prove that a smooth de current and a sinusoidal ac current are obtained, and that a great reduction of the de inductance can be achieved by using the proposed converter. (C) 1998 Scripta Technica.