Grid Integration of Pv Systems and Local Storage in Distribution Networks

In this Master thesis the integration of PV systems and Battery Energy Storage Systems (BESS) in the distribution grid is examined. The simulation framework and the algorithms that were implemented in this thesis are applicable to general distribution grids. However, the main focus of this thesis is to study the concrete example of a distribution grid in the city of Zurich. The electric utility of the city of Zurich (ewz) has initiated the pilot project BESS Dora-Staudinger-Strasse. In this project a BESS is installed in a distribution grid that consists of loads and PV systems. In the current configuration the grid is fed by three transformer stations. When the BESS is installed, a new grid configuration can be tested: two transformer stations will be disconnected and the remaining transformer station will supply the entire load. Consequently, the loading of the lines and transformers will increase. The main goal of the project is to determine how the safe operation of the grid can be ensured with the BESS in the experimental grid configuration. If the project is successful, future grid expansions due to load increases or newly installed PV systems could be replaced by the installation of a BESS. In the first part of this thesis the dimensioning of the BESS is discussed. Initially, a simplified grid independent model is studied. An algorithm is presented which determines the minimum amount of storage capacity that is needed to reduce the loading of the cables below a specified threshold. In the future load increases due to the introduction of electric vehicles are expected in the distribution grid. The effects of future electromobility on the dimensioning of the BESS are also presented in this thesis. In the second part of the thesis the operation of the BESS is discussed. It could be verified that the storage capacity of the BESS is sufficient to ensure the safe operation of the grid in the experimental configuration. Since forecasts of the load and the PV generation must be taken into account for the optimal dispatch of a BESS, a model predictive control (MPC) scheme was used. In this thesis an algorithm which maximises self-consumption and a peak shaving algorithm were implemented. The advantages and disadvantages of the two algorithms are described in this thesis.