Design and analysis of a DC/DC/AC three phase solar converter with minimized DC link capacitance

Solar converters to feed the energy from the solar module into the AC grid consist of a DC/DC and a three phase DC/AC converter decoupled by a capacitor in the DC link which is to be minimized. A current fed instead of a voltage fed full bridge DC/DC converter is chosen and leads to a higher efficiency. Furthermore undesirable voltage spikes can be avoided by the use of this topology. This paper presents a control concept without additional sensors to reduce the DC link capacity in solar converters and its analysis. Two different analytical methods to determine a minimal DC link capacity are explained. The proposed control method to reduce the voltage deviation in the DC link can be implemented without additional sensors in most of solar converter applications. It can also be adapted to other DC/AC converter applications like converter systems for fuel cells. Laboratory measurements confirm the simulation results.