A Control Algorithm for a Heterogeneous Virtual Battery Storage Providing FCR Power

We consider a virtual battery energy storage consisting of individual storage systems used for both, maximization of household PV-power own-consumption and provision of frequency containment reserve power. The frequency containment reserve power provision is managed by a central controller by setting benchmarks for each individual storage and also autonomously by each individual system based on the frequency deviation to its nominal value. In previous work, we showed that in such a system, a uniform frequency containment reserve power dispersion to all individual storage systems causes high losses due to the bad efficiency of the rectifiers in low part-load operation and that this issue can be solved by only using subsets of the virtual battery energy storage for frequency containment reserve power provision. This paper suggests a generalized control algorithm, which is also applicable in systems with heterogeneous individual storages and can easily be parametrized and utilized in different systems. We show analytically that the algorithm disperses the power in a way that each participating unit operates close to the optimal operating point no matter the power limits and energy contents of the individual storages. We also show in detailed simulations that this new algorithm works better than the previously proposed one in case of homogeneous systems.