What is LeMoStore for?

With LeMoStore, a modular energy storage system is created that simultaneously serves as a converter for the power grid.

The power grid requires converters that convert direct current into alternating or three-phase current (and vice versa). This is relevant, for example, for photovoltaic systems that provide direct current. However, three-phase alternating current is common in the power grid, so conversion is necessary. Renewables in particular also have the characteristic that their electrical output is weather-dependent, for example. To compensate for this, energy storage systems are an important component in the power grid. For LeMoStore, lithium-ion batteries are therefore integrated into the structure of a modular multilevel converter (MMC). The structure of the MMC allows high-quality three-phase AC power to be provided, as well as other DC sources and storage to be connected to the power grid. The converter's power electronics can also be used for optimal operation of the integrated energy storage devices.

Factors influencing aging such as the number of cycles, longer-term charge levels and maximum currents can thus be influenced. To maximize the lifetime of the battery modules, LeMoStore uses novel modeling approaches to operate batteries of different types and ages in the MMC. By strategically dividing the charging and discharging power, the maximum service life is achieved and even battery cells that are already in use can be individually loaded and thus used for even longer. In addition, the optimized operation enables the reduction of the installed storage capacity and thus the realization of economically more favorable systems with identical characteristics. The developed system will be tested as a demonstrator in the PHiL laboratory of the Energy Lab 2.0.