High Efficiency DC-to-AC Power Inverter with Special DC Interface

In case of medium voltage (several tens up to hundred volts on DC-side) solar inverter applications, a DC-to-DC converter for voltage level adaptation is required in series of the DC-to-AC inverter. This leads to a two-stage concept with accumulation of the losses. In our case a concept was chosen where the efficiency of each stage is maximized by using the best topology. The given requirements make the application of a non-isolated design imperative to avoid additional transformer losses. In this paper a 60V–120V DC (input) to 230V AC (output) / 1kW converter with minimal conversion losses is derived. A simple modification in the inverter's output section leads to a significant improvement of the losses in the inverter system. Only three additional components (two diodes and one inductor) are necessary to optimize the inverter's power stage. The topology presented here shows a remarkable improvement of the switching losses and significantly reduced EMC. It is well-suited for solar power inverter applications.