Your own power grid AC and DC solutions for stand-alone systems


Electrical current, anytime, anywhere – something we all take for granted. More than two billion people, however, live in another reality: in so called "remote areas", far away from power plants and electrical grids. And for this reason, they must do without many of the conveniences of our civilization. Photovoltaic energy offers solutions like no other technology: PV plants are robust, du- rable, easy to install and maintain. For years SMA has been motivated to develop a self- contained energy supply system based on solar power. SMA is the only manufacturer in the world to pursue not only the concept of DC coupling, but also AC coupling, which has a range of advantages. With AC coupling, all loads and generators are con- nected using an AC voltage bus, whereas with DC coupling, the interconnection takes place in a DC voltage grid. For residen- tial as well as industrial power generation, AC coupling has been used throughout the world, while DC coupling systems have


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been employed mostly in small applications of up to 100 watts as well as for telecom- munications purposes.


Different Types of Coupling


There are three different concepts for estab- lishing energy supply systems, which save the generated energy in batteries: pure DC coupling, mixed systems, and pure AC cou- pling. In the beginning, the first develop- ments relied on pure DC coupling: both the solar modules and the batteries were DC voltage sources, so that a conversion of the power with the then still expensive inverter technology could be avoided. With a few hundred watts of power, the performance of this system was quite low and many of the appliances consuming the energy, such as lamps, radios or televisions, were also available in DC voltage versions.


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