A high-power-factor PWM rectifier without voltage sensors

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 have been studied to simplify the system configuration and control of such rectifiers. It is known that a voltage detector on the ac side can be omitted, though a voltage detector on the de side is needed for adjustment of the de output of a PWM rectifier. In this paper, a method for controlling a single-phase rectifier without any voltage sensor 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 multiplying the inductance of the reactor by the derivative of the source current measured. The de 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, its implementation, and the performance characteristics of the rectifier. The usefulness of the rectifier is confirmed by experiment. This method is applicable to various types of PWM rectifiers. (C) 1997 Scripta Technica, Inc.