The new MOSFET-generation with SiC-materials seems well suited for power electronic converters up to 1200 V operating-voltage, and particularly for grid-feeding PhotoVoltaic-inverters, which transfer the DC power of the solar panel to the AC grid. Their high switching speed and low on-resistance RDS(on) allow the use of higher switching frequencies, which could mainly reduce the costs and weight of the converters. This paper shows a comparison between IGBT and SiC DMOSFET devices and first measurements of some 1200 V / 10 A SiC-DMOSFET samples made by CREE®.

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The total amount of photovoltaic (PV) energy production in the global energy mix has been increasing strongly all over the world in the last decade. This phenomenon has been mainly driven by the promotion of renewable energies, as well as by the well known feed-in tariffs. Although the major part of PV installations consists in roof mounted panels in private, collective or commercial buildings, the amount of large scale PV power plants, from 200 kW to 10 MW or more is increasing drastically. Such large scale PV power plants already represent nearly 20 % of the total installed PV capacity. Indeed, by reducing of the overall system costs, they are becoming serious alternatives to fossil fuel or nuclear power plants for utilities. [GRAPHICS] Taking into account that a sun tracking system can substantially improve the daily energy production of flat plate modules (approx. 10% to 50%), and that such a tracking unit is absolutely necessary for concentrating photovoltaic systems (CPV), one understands its crucial role for solar power plants. One or two axis solar trackers already represent 27% of the total power plant capacity worldwide in 2008. This part is increasing constantly since the additional investment costs for the mechanics are relatively inexpensive compared to PV. Especially for CPV systems, the control unit of a solar tracker has to provide reliable and precise positioning; hence controlling one or two drives to move the panels in a restricted angle window to the sun (typ. 1 degrees to 0.1 degrees). In principle, such a positioning unit consists of a calculation unit (e.g.: mu C or DSP), a power unit driving the motors and a feed-back circuit for different kinds of sensors (e.g.: position or irradiance sensors). Consequently, integrating those functions into an already existing inverter, which feeds the PV power of one tracking unit (typ. 5 kW(p) to 40 kW(p)) into the grid, allows plenty of interesting advantages that will be pointed out in this paper

Currently there are several silicon carbide (SiC) field effect or bipolar transistor types in development with normally-on and normally-off characteristics. It is not yet clear, which transistor type will prevail in the market and which will remain a niche product. This is not only determined by their electrical characteristics, but also by their acceptance by engineers. In this paper the implementation and the performance of 1200 V / 20 A / 100 m SiC-DMOSFETS and 1200 V / 12 A / 125 m normally-off SiC-JFETs in photovoltaic inverters (PV-inverters) is shown.

This paper presents a new inverter topology named after its operating principle based on a flying capacitor. The inverter uses neither a grid transformer (50/60 Hz) nor a high frequency transformer and therefore does not provide a strict galvanic isolation. However, its innovative circuit has been designed in order to allow grounding one pole of the photovoltaic (PV) generator which is not feasible with common transformer-less PV inverters. The slight drop in efficiency and increase in size and costs due to the use of more numerous semiconductors and additional passive components is well below that of inverters using high or low frequency transformers and is fully compensated by decisive technical advantages. Indeed, the ability to ground the DC side of the inverter can be of a great interest for certain PV generators but also for other kinds of applications such as batteries