The Impact of a Distributed Battery Energy Storage System on Transmission and Distribution Power Grids

This thesis reports on an investigation of the impact of battery energy storage systems (BESS) on the voltage and frequency stability of a transmission system. It also explores an application of a BESS into an active distribution system which delves the realm of smart grids. Power quality and system stability are two major concerns in the transportation and distribution of electrical energy. It has long been recognised that energy storage is a possible way forward to improve on these parameters; but the battery technology and the ancillary power electronics had not been developed sufficiently, until quite recently; to meet such expectations. Current battery energy storage challenges the paradigm of instantaneous usage of electrical energy. Intermittent renewable energy production has the potential to improve the quality and efficiency of energy production. The thesis gives an explanation of the battery working principles and includes a com-parative study of battery technologies and the main advantages and disadvantages of batteries in comparison to other electrochemical energy storage technologies. Besides, the thesis addresses the all-important issue of power electronic converters. Battery con-verters are responsible for controlling the power exchange between the grid and the BESS. The link between the battery and the DC bus, i.e., DC-DC converter, and the link between the DC bus and the grid, i.e., DC-AC converter, are covered in depth. It has been found that using a BESS in a transmission system significantly improves frequency stability. The damping of oscillations following a transient event is much improved. The BESS can be seen as additional spinning reserve in the system. On the other hand, when a BESS is applied in an active distribution system, the power, deliv-ered by an intermittent energy source is of much higher quality. In particular, it is shown that the BESS has the potential for turning a part of the distribution system with intermittent generation, self-reliable from the energy perspective In brief, the outcome of this thesis shows the positive influence of the BESS in electrical powers grid. Further research is required to develop a more detailed model of the battery which would include battery ageing and temperature dependency