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.

One Cycle Control of A PWM Rectifier a New Approach

“…To avoid this, OCC has sacrificed its simplicity again as they use input voltage multiplexers, and other additional analog and logic circuits [43], [23], [28], [42], [25], requiring the knowledge of 600 angular sectors and to select positive and negative peak voltages as reference current vectors. In [29], [41] was also necessary to sacrifice OCC simplicity by adding a few analog multipliers and heavy and bulky inductors (10mH), but sacrificing the cost-effectiveness of OCC solution. Hence, despite all the efforts, it is apparent that, to date, OCC has been not able, whatsoever, to solve its own problems fully.…”

“…Hence, despite all the efforts, it is apparent that, to date, OCC has been not able, whatsoever, to solve its own problems fully. Above all, even though a few hardware methods have solve partially OCC stability issues at no-load [21], [38], [39], [26], [41], and at high-load [43], [29], [42], [25], they were never reported working together over a wide load range. Thus, one of the paper's major contributions is to present a simple and stable OCC system working at no-load and high-load.…”

Grid Voltages Estimation for Three-Phase PWM Rectifiers Control Without AC Voltage Sensors

“…This ensures uninterrupted operation in case of sensors failure. Besides obvious benefits of sensors reduction, there are several other additional advantages like [4], [8], [11], [13], [14]; elimination of noise, resolution limitations, offset and various disturbances related to sensors, and decrease of hardware complexity. ACline current sensors and DC-link voltage sensor are essential for proper operation of the control system since the AC-line currents and DC-link voltage are the controlled quantities [9].…”

“…In [11], ROGI based control scheme has been modified to achieve sensorless operation. One cycle control designed using hardware circuits instead of a digital algorithm has been presented in [8]. Recent algorithms based on virtual impedance emulation [4] and mathematical optimization [6], [7] have been investigated.…”

“…Although the cited strategies provide satisfactory results, some of them require specific control schemes [8], [11], [14], [24], [28]. Others are sensitive to load variation [4], need initialization [7] and present instability under grid voltages sag [8] which deteriorate their robustness. The VF estimation through open loop integrators has limitations related to stability [9].…”