A novel strategy for composing staircase waveform in multi-module inverters

In multi-module inverter systems, phase-shifting transformers are needed to compose non-sinusoidal voltages into staircase waveforms approaching sinusoid. Aiming at the drawbacks of normal phase-shifting transformers with respect of installation and operation, the paper proposes a novel transformer of round shape resembling induction motor. Contrast to the normal phase-shifting transformers, the iron core of the novel one is more compact and symmetrical, and the windings distribution and connection are simpler. Focusing on novel transformer of dual Y/Y, the paper theoretically proves that harmonics of the 5^th, 7^th etc. are eliminated from the composed magneto motive force (MMF). Mathematic model of the novel transformer is set up and simulated numerically for exhibiting the main performance.