Simulation and Analysis of Single-phase Multistage DC-AC Inverter with Medium-frequency Transformer Isolated DC/DC Converters

With the advancement of power electronics technology and the growing demand of renewable energy harness, solid-state transformer (SST), as an emerging transformer technology, has garnered significant attention. This paper proposes a control strategy based on state space averaging method (SSAM) for a DC/AC converter formed by two parts, one being mediumfrequency transformer isolated DC/DC converters while the other being single-phase multistage DC-AC inverter. The first part in such a SST is controlled by comparison of reversed triangular waveforms with the same reference signal to produce two pairs of switching signals. For the second part in the SST, the same circuit topology is controlled by two different methods to make it work as a current-controlled voltage source inverter or a voltage-controlled voltage source inverter. MATLAB was utilized to validate the proposed theory. The modeling results demonstrate that the proposed control method effectively enhances the stability of these structures while ensuring balanced output voltage across each of multistage in the single-phase inverter.