Efficiency Optimized, EMI-Reduced Solar Inverter Power Stage

In the field of electrical solar power conversion efficiency is the most important topic. In most applications a special DC-to-DC converter is necessary to couple the solar cells, operating at low DC-voltages, to the inverter's DC-link. These converters with rather low input respectively high output voltage ratings have, due to the high current ratings, a relatively low efficiency. Furthermore conventional power inverters used in mains connected applications fight with the disadvantage of the hard switched PWM power stage. Alternatively, also soft switching topologies would not give full benefits. A simple modification in output section of a hard-switched topology, however, can lead to a significant improvement of the system losses. Only two additional components (diodes) are necessary to optimize the power stages for usage in a mains coupled inverters. The topology presented in this paper shows a remarkable improvement of the switching losses as well as a significantly enhanced EMC. Consequently, it is well suited for solar power inverter applications.