Pulsewidth modulation (PWM) control techniques for rectifiers are widely used to improve the source current waveform and the input power factor. Recently, methods to reduce the number of detectors are studied to simplify system configuration of such rectifiers and their control. It is known that a voltage detector on the ac-side can be omitted though a voltage detector on the dc-side is needed for adjustment of the dc-output of a PWM rectifier.
In this paper, a method for controlling a single-phase rectifier without any voltage sensors is proposed. The ac-side voltage can be estimated from the input-reactor voltage when the ac-side of the bridge is short-circuited; the reactor voltage is easily obtained by multiplication of the inductance of the reactor and the derivative of the source current measured. On the other hand, the dc-side voltage can be estimated by calculating the difference between the source voltage at the beginning of every switching period and the reactor voltage sampled and held in the previous bridge conduction mode.
This paper describes the control scheme and its implementation, and performance characteristics of the rectifier. The usefulness of the rectifier is confirmed by experiment. The method is applicable to various types of PWM rectifiers.