Small and micro-power plants such as CHP plants, photovoltaic systems and small wind turbines are increasingly contributing to power generation. In contrast to, for example, large-scale wind turbines, these mostly feed electricity directly into the low-voltage grid but do not support the grid by providing system services such as controlling the output or frequency, maintaining the voltage range, providing reactive power or improving grid voltage quality. Today, such services are almost solely provided by large-scale power plants.

For grid operators, the growing number of decentralised energy systems is presenting a new challenge. They have neither control nor knowledge of the current amount of electricity fed in by the individual plants. There are no control devices connecting the decentralised energy systems to the low-voltage grid, so that the grid operators are unable to monitor or control the feed-in situation but can only make forecasts.

If, under these conditions, the proportion of uncoordinated decentralised energy systems is too high relative to the overall generation, this can endanger the secure and optimum operation of the grid.

Various research projects have shown, however, that decentralised energy systems can also contribute to optimum grid operation if the corresponding measurement equipment is available and suitable energy management systems control the generation and consumption in the distribution networks. Here centralised control concepts are competing with systems that optimise the electricity feed-in and consumption decentrally.

The DINAR research project, funded by the Bundesministerium für Umwelt, the German Ministry for the Environment, shows how this decentralised energy management can be implemented. Together with seventeen industry partners, the Institute for Solar Energy Supply Technology (ISET) has developed a bi-directional energy management system for the low-voltage grid.