AN3152 Datasheet, PDF (1/17 Pages) STMicroelectronics – The right technology for solar converters

AN3152
Application note
The right technology for solar converters
Introduction
Following a short overview of types of solar power systems and converters, this application
note introduces a fully working, grid-connected solar inverter prototype suitable for rooftop
applications. This solar inverter has been equipped with STMicroelectronics’ MDmesh™
and silicon carbide (SiC) devices to allow evaluation of these products in “green”
technologies.
Thanks to ST’s newest technologies (MDmesh™ V and SiC) and a new converter
philosophy, a 650 V fast power MOSFET can be used to boost performance and reduce the
size of the converter. A stage-by-stage explanation is presented here, as well as the
topologies adopted, and a detailed analysis of the front-end stage of the inverter is
discussed. The BOOST stage is used as a case study to validate the performance of the
new power MOSFETs and diodes.
Everyone is thinking “green’ these days. Adding to the new green conscience are the
increasing costs of fossil and nuclear fuels, prompting the market to turn to creative
technologies that use renewable resources to produce energy. Energy produced from
renewable resources are becoming an important contribution to the world’s total energy
demand and will increase in the next decades. Solar photovoltaic technology represents one
of the most promising energy resources, due to its low environmental impact and high
reliability. Every photovoltaic (PV) system consists of a module array and an inverter. The
inverter module is mandatory on all grid-connected applications, in order to amplify the low
DC voltage generated by the module to the higher AC level required by the grid. If several
modules are connected in series it might not be necessary to include amplification, but in
any case a maximum power point tracking (MPPT) function is required.
This prototype has a wide operating input voltage range (from 200 V to 400 V), and 3 kW of
maximum power output, since it is intended for rooftop applications. Total efficiency must be
at least 97%, and an MPPT function is implemented in order to enable panels to work at
their highest efficiency. In fact, the PV module (or modules, if connected in series) changes
its maximum power point continually during normal operation due to the variances in solar
radiation caused by shade or weather.
May 2010
Doc ID 17056 Rev 1
1/17
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