PLL-less one cycle controlled bi-directional high power factor ac to dc converter

Abstract

Ac to dc converters based on one cycle control (OCC) exhibits instability in current control at light load conditions as well as when it is operating in the inverting mode. In this paper a modified OCC for a bi-directional ac to dc converter is proposed. The proposed technique neither requires the knowledge of the 60° angular sectors of input voltage nor it requires the service of additional multiplexers or any other complicated circuitry. A fictitious current component in phase with the utility voltage is synthesized. The sum of this current component and the actual load current is compared with the triangular waveform to generate the gating pulses for the switches. This modification not only renders stability to the converter at light load conditions and inverting mode of operations, but also enable the converter to transfer its operation seamlessly from rectifying mode to inverting mode and vice versa. Detailed simulation studies are carried out to verify the effectiveness of the proposed scheme. In order to validate the viability of the scheme, detailed experimental studies are carried out on a scaled down 2 kW laboratory prototype developed for the purpose.