WG C6.30 The Impact of Battery Energy Storage Systems on Distribution Networks
Battery Electric Energy Storage Systems (BESS) are being used in distribution networks to improve operational efficiency, postpone or eliminate the need for large capital expenditures to upgrade networks, and enable greater integration of renewables. Unfortunately, there is a lack of guidelines and recommended practices on how these systems should be integrated into the distribution networks. Working Group C6.30 “The Impact of Battery Energy Storage Systems on Distribution Networks” was established to address this issue and the findings have recently been published in Technical Brochure 721. The Australian members on the WG were Michael Negnevitsky and Alex Baitch.
As countries transition towards a low carbon economy there has been a significant increase in the use of renewable energy sources often based on wind and solar power. Those energy sources are intermittent by nature and introduce stability, operation, control and power quality issues into the network. The use of BESS can help in mitigating these problems. Australia has a target of at least 20% of electricity to be supplied by renewable generation by 2020, and in some areas the network is already experiencing challenges associated with this ambitious program. While the benefits of storage to balance the intermittent nature of wind and solar are well known, the fast response of batteries to assist with security of supply is now receiving increased attention. For example, a 100MW/129MWh battery has recently been installed in South Australia to help address grid stabilisation issues related to renewable integration.
The Working Group focused on the following topics:
1) Planning and design;
2) Operational considerations;
3) Use-cases and business cases;
4) Standards and Grid Codes;
5) Practical international experiences.
In recent years, it was demonstrated that BESS can be used for primary frequency control in MV/LV microgrids. This development is particularly relevant to Australia, as the majority of battery storage in Australia is installed off-grid. A microgrid is a small-scale power system that consists of micro sources (photovoltaic generation, wind generation, small diesel generators etc.), storage units and loads and is operated in two modes: grid-connected or islanded. In the islanded mode, the frequency of the system can change very rapidly because of the low inertia within the microgrid. As a result, primary frequency control becomes a vital task that can be addressed by BESS.
Another interesting recent development is the use of BESS for alleviating grid congestions. Increasing renewable energy penetration at the distribution level can result in high values of currents and voltages that may exceed circuit ratings. Optimisation of the BESS charging and discharging strategies can mitigate the grid problems, reduce the need to curtail renewable generators and ensure required quality of power supply in the distribution networks. However, to achieve the desired effect, the BESS units should be placed strategically in the grid.
The Technical Brochure reports on several successful applications of BESS for peak shaving and load levelling that can lead to deferment of investment at the generation, distribution and transmission levels. Energy storage provides a fast response, making it the optimal solution for this application. Note that peak shaving installations are often owned by the electricity consumer, rather than by the utility and the increasing number of participants in this relatively new field requires further development of market and regulatory systems.
The Technical Brochure (TB) 721 can be viewed on e-CIGRE and is free to members.
The cost to non members is € 230.