A hybrid current controller for a 1-phase PWM rectifier combining hysteresis and carrier-based schemes to achieve a zero current error and unipolar PWM waveforms

摘要

A current controller is described for 1-phase PWM rectifiers that combines both the functionality of hysteresis-based and carrier based controllers. The development of this current controller is described with the aid of generic PWM controllers that use a sinusoidal modulating signal and a signal integrator. These controllers mimic the operation of the 1-phase PWM rectifier and are used to determine the optimal gain-constant associated the current-error feedback signal. The resultant current controller is relatively insensitive to variations in rectifier parameters such as the supply inductance and the dc link voltage magnitude. The controller combines the excellent current waveshaping ability of hysteresis-based controllers together with the constant switching frequency of carrier-based controllers. The main controller features include: real-time generation of the sinusoidal amplitude modulation signal from the PWM signal; elimination of phase-shifts caused by the limited rate-of-change of the rectifier current; a near zero current-error over a PWM half-cycle; no skewing effects in the current-error signal. Simulation results, using a per-unit system of values, are used to illustrate the step-by-step development of the current controller. A DSP-based controller is used, together with an IGBT rectifier, to demonstrate the experimental operation of the controller.