Power conversion system with stepped waveform DC to AC converter having prime mover start capability

A power conversion system utilizing a generator having armature windings and coupled to a prime mover wherein the power conversion system is operable in a generating mode to convert motive power developed by the prime mover into electrical power and in a starting mode to convert electrical power developed by a source of AC power into motive power for starting the prime mover, comprising:

• a rectifier bridge having an input and an output;
• first, second, third and fourth inverters each having an input and an output and including a plurality of switches and a plurality of flyback rectifiers coupled across the switches;
• a transformer including first, second, third and fourth sets of primary windings and a set of secondary windings wherein the first set of primary windings is coupled to the output of the first inverter;
• an interphase transformer having first and second ends and a mid-tap;
• and
• means operable in the generating mode for coupling the rectifier input to the generator armature windings, the inputs of the first through fourth inverters to the rectifier output and the second through fourth sets of primary windings to the outputs of the second through fourth inverters, respectively, and operable in the starting mode for coupling the source of AC power to the set of secondary windings, the third set of primary windings to the output of the first inverter, the second and fourth sets of primary windings to the input of the rectifier bridge, the output of the rectifier bridge to the first end of the interphase transformer, the input of the first inverter to the second end of the interphase transformer, the mid-tap of the interphase transformer to the inputs of the second through fourth inverters and the output of the second inverter to the generator armature windings;
• and
• means coupled to the inverters for operating same so that AC power produced by the generator in the generating mode is converted into DC power by the rectifier and the DC power is converted into fixed frequency AC power by the inverters which is developed in the set of secondary windings and so that AC power induced in the sets of primary windings due to application of AC power to the set of secondary windings in the starting mode is converted into DC power by the flyback rectifiers of the first inverter, the rectifier bridge and the interphase transformer and the DC power is converted into AC power at a controlled frequency by the second inverter which is applied to the generator armature windings.