One-cycle-controlled bidirectional three-phase unity power factor ac–dc converter without having voltage sensors

Abstract

One-cycle-controlled ac-to-dc converters exhibit instability in current control at light load conditions and while they try to operate in the inverting mode. A one-cycle control (OCC)-based scheme has been reported in the literature which overcomes the aforementioned limitation. However, the controller for the scheme presented in the literature needs to sense instantaneous phase voltages of the utility. In an effort to dispense with the voltage sensors of the OCC-based bidirectional converter, a voltage-sensorless one-cycle-controlled bidirectional ac-to-dc converter is proposed in this study wherein the information regarding the instantaneous utility voltages are synthesised within the controller and hence they are not required to be sensed. Instantaneous phase voltages of the utility are reconstructed by filtering pertinent switching sequences (gate pulses) of the converter through second-order band-pass filters. Rigorous analysis of the proposed scheme is carried out. Detailed simulation studies are carried out to demonstrate efficacy of the proposed scheme. In order to verify the viability of the scheme detailed experimental studies are carried out on a laboratory prototype developed for the purpose.