Proper topology for simple single phase inverter quasi sinusoidal which consist of combined square inverter

In developing countries like Indonesia it is not easy to find core material such as ferrite or thin laminate for high frequency use. The need of single phase sinusoidal inverter of 50 Hz or 400 Hz should be with some criteria cheap, easy to find raw material, simple and having fewer components. The proposed converter is based on a single phase square inverter. By making the connection of some inverters properly where the output of the secondary in series and input side of the transformer in parallel. To have minimum THD, it should have displacement conduction among the square inverter. With a displacement angle of the second inverter at 25° and the third one at 48° and pulse width conduction of 147° the THD could be less than 5%.