Control and design principle of a soft-switching boost dc to ac converter without smoothing capacitor using a MERS pulse link concept

One of challenges in power conversion with conventional topologies is a large smoothing capacitor. Authors have proposed a soft-switching boost dc/ac converter, which is a combination of an inverter and a pulse voltage generator working as a step-up chopper. The pulse generator generates high frequency pulse voltage from a low dc voltage using resonance of relatively small inductor and capacitor. The inverter distributes this pulse to phases of an ac load without smoothing it; therefore, the proposed converter does not need any smoothing capacitor. Another advantage of the proposed converter is soft-switching operation of all semiconductor switches. On the other hand, this converter has difficulty in power control, one of examples is observed as significant fluctuation in the pulse link voltage. This paper discusses control methods to reduce this fluctuation, and a design principle with this proposed control.