Advanced management of residential battery energy storage in future distribution networks

Abstract

In recent years, Australia and many other countries have seen a sharp rise in the number of residential solar photovoltaic (PV) system installations. This trend has also driven the adoption of residential battery energy storage (BES) systems, as they allow households to use their excess PV generation at other times. However, as it currently stands, most commercially available residential BES systems are controlled for the sole benefit of their owner, i.e., to reduce grid imports. But given their controllability, there exists a large opportunity for these systems to a) help mitigate the well-established PV issues in electricity distribution networks (e.g., voltage and thermal issues), or b) be used in the provision of services to the whole power system (e.g., frequency or energy services).

For a), this thesis first assesses the performance of off-the-shelf (OTS) BES systems and demonstrates their inability and limitations to provide support in mitigating PV impacts. While overcoming these limitations has been the focus of several studies over the past years, there is need for practical and scalable, yet effective BES control strategies that provides benefits to both the customers and the distribution network to be developed. In this context, a decentralised control of BES systems is proposed which dramatically reduces PV impacts on the distribution network with minimal effects on households.

As for b), in this thesis, the impacts of the widespread provision of services from residential BES systems on distribution networks are assessed. It is demonstrated that if left unconstrained, it can lead to severe issues. In this context, a distribution system operator (DSO) framework is proposed, using a three-phase AC optimal power flow-based approach, to ensure network integrity and fairness. The results show that it is not only possible to achieve this for multiple service providers, but it also unlocks much larger volumes of services compared to those achieved with the currently adopted fixed export limits of 5kW per phase.

To assess the network performance as realistically as possible, this thesis uses an integrated medium voltage (MV) – low voltage (LV) network to consider the interactions of multiple voltage levels and fully capture the effects of DER (and the resulting reverse power flows). More specifically, a 22kV (i.e., MV) real feeder is used from Victoria, Australia, whereas the 400V (i.e., LV) circuits are modelled based on regional network design principles. Furthermore, the analyses utilise real smart meter demand, generation, and pricing data from the same region. The power flow assessments consider high granularity time-series data using three-phase four-wire unbalanced power flows. Finally, a Monte Carlo approach is adopted in the assessments in this thesis to cater for the uncertainties related to demand, generation, and locational aspects of distribution networks.