Question

Explain about three-phase resonant converters ?

Answer 1

The three-phase resonant converters offer an attractive solution to high-power DC supplies owing to area reduction in component stresses as compared to single-phase resonant converters of the same power rating. For high power level, single-phase resonant converters face severe voltage and current stresses. In case of a DC–DC converter using a three-phase modified series–parallel resonant converter (MSPRC) is proposed. There are many advantages of this converter, such as lower inverter output current, lower voltage stresses, reduction in size of magnetic components, narrow variation in switching frequency for the output voltage regulation and better power conversion efficiency owing to reduced conduction losses. However,studies on the performance evaluation of three-phase MSPRC configurations have not been reported previously in the literature. Hence,a DC–DC converter using three-phase MSPRC is proposed for carrying out the analysis. A systematic procedure is used to design the converter components. The converter performance is evaluated using a variable-frequency control method for the output voltage regulation. The converter is operated at the minimum switching frequency of 290 kHz at full-load condition to increase the power packing density. Thus the minimum ripple frequency at the output is 1.74 MHz.Therefore the ripple amplitude is very small and the filtering requirements are reduced drastically. The inverter switch currents decrease with the load current. This helps to maintain good efficiency at light loads. Also the conduction losses in the three-phase high-frequency (HF) inverters switches are less, since the average current through the switch is reduced as compared to a single-phase configuration for the same power output. This results in higher power transfer for the same switch current and voltage stresses.The converter maintains lagging power factor mode ensuring zero voltage switching (ZVS) throughout the load range.Thus three phase converter has several advantages over single-phase converters, which include reduction in filtering requirements narrow variation in switching frequency for output voltage regulation, suitability for high–power applications, high–power conversion efficiency due to reduced conduction losses etc.