Wide-band gap devices in PV systems - opportunities and challenges

The recent developments in wide band-gap devices based GaN and SiC is showing a high impact on the PV-inverter technology, which is strongly influenced by efficiency, power density and cost. Besides the high efficiency of PV inverters, also the mechanical size, the compactness and simple structure have an important role in the cost reduction. To increase the efficiency of PV systems, most of solutions for PV inverters have moved to three-level (3L) structures reaching typical efficiencies of 98% due to low switching losses of 600V Si IGBT or MOSFET and reduced core losses in the filter. With the appearance of SiC 1200V MOSFETs, it becomes possible to return to more simple two-level (2L) structure with comparable efficiency but high potential to reduce the overall cost. This paper deals with a comparison study between a Si-based 3L-Diode Neutral Point Clamped (DNPC) and a SiC-based 2L-Full Bridge (FB) three-phase PV-inverter topologies in terms of efficiency, thermal loading distribution and costs. Moreover the above mentioned PV-inverters are built and tested in laboratory in order to validate the obtained results.