Distributed Battery Storage (DBS) in Low Voltage (LV) grids is an attractive solution for house owners to increase their self-consumption from photovoltaics (PV) and for Distribution System Operators (DSOs) to defer line upgrades. This project aims at finding and quantifying optimal operating and planning schemes for DBS and for different business cases.

This project proposes novel methods to improve the integration of DBS in LV grids in conjunction with a high PV share. The first goal focuses on the improvement of operation schemes for DBS applications. Model Predictive Control (MPC) strategies are developed using linearized optimal power flow approximations. It is shown that these strategies increase significantly the operational revenue as compared to conventional control schemes. As a further finding, by including battery degradation models into the control framework, the revenue and battery lifetime can be further increased.

The second objective of the project deals with the question where should DBS be located and how big should be the size of DBS? From the case studies, it follows that the MPC control horizon greatly affects the profitability. Moreover, for a market-based DBS application, it can be anticipated that distributed storage configurations are more preferable than centralized configurations, since the impact on the mitigation of PV curtailment outweighs the benefit of reduced network losses from energy arbitrage. However, the optimal DBS configuration is highly dependent on the grid topology, application and generator configuration, such that quantitative conclusions on the optimal battery distribution can only be drawn for particular settings.

Figure 1:  Proposed optimization framework that combines operational aspects with planning considerations of DBS.

These results are the outcome of a PhD thesis that was written by Dr. Philipp Fortenbacher and was supervised by Prof. Göran Andersson, former ESC member and former head of the the Power Systems Laboratory (PSL) at ETH Zurich. The PhD thesis is available at the ETH research collection. Philipp Fortenbacher is now Post Doc at the Research Center for Energy Networks (FEN).