An AC-AC Converter Topology with Low Voltage Stress on Transistors for Aircraft Applications

AC-AC converters are widely used in aircraft applications to generate desired voltages with variable frequency. Yet, the maximum voltage stress on transistors in the existing topologies is at least the amplitude of the input line-to-line voltage, which is relatively high and thus is a critical concern for aircraft applications demanding high reliability. Therefore, this paper proposes a novel AC-AC converter topology with low voltage stress on transistors, which comprises a current source rectifier (CSR) and a voltage source converter (VSC). In particular, the freewheeling diodes and capacitors on the DC side of CSR are split into two series-connected parts, while their midpoints are connected to the neutral point of input filter capacitor through a small capacitor, as well as to the neutral point of output filter capacitor. The corresponding analytical derivations of transistor voltage stresses are provided. Compared with the traditional converter, associated with the proper modulation scheme, the proposed topology can reduce the voltage stress on the CSR transistors by 48.0% and the VSC transistors by at least 13.4%. Therefore, low voltage stress on transistors enables this topology to utilize high-performance devices with lower voltage ratings. Experimental results have verified the validity and effectiveness of the proposed topology.