Control strategy for multifunctional, three-phase, four wire, AC-DC boost converter

This paper presents control strategy for multifunctional, three-phase, four wire AC-DC converters. The converter is named multifunctional because it operates as a battery charger and as a load power supply. In other words, two different loads in parallel are connected simultaneously to the converter. For this purpose same current and voltage signals are necessary to send to the control circuit. The indicated signals are, input main currents, output load currents, battery bank currents, voltage across of each battery bank, total output voltage, and input main voltages for feed-forward networks and current shape. The proposed converter control strategy is applied in non-isolated three-phase UPS systems. The relevant features of the proposed converter control strategy are, power factor correction, common neutral point between input and output to facilitate bypass circuit installation, symmetrical divided output voltage for inverters with neutral point, and battery current control with high power factor. Principle of operation of the control circuit and experimental results obtained from a small power scale prototype are presented.