Energy storage in the distribution system to reduce constraint and curtailment of renewables

The governments of Northern Ireland and Republic of Ireland have set the most ambitious targets in the European Union to supply 40% of electricity consumption from renewable generation by the year 2020. On the island of Ireland renewable generation is presently dominated by wind generation and this is likely to remain the case for the foreseeable future. Presently we can meet approximately 20% of our electricity needs from wind generation but system operational rules do not allow generation from non-synchronous sources, such as modern wind turbines, to exceed 50% of the island load. Once the level of system non-synchronous penetration (SNSP) reaches 50% it is therefore necessary to limit the infeed of wind generation, through a process known as curtailment.

In addition, due to the level of wind generation already connected to the grid, grid congestion is becoming more prevalent and at times this gives rise to the necessity to constrain the output from some of the wind turbines. As the installed capacity of wind generation continues to grow, so too does the necessity for wind curtailment and constraint. This equally applies to other stochastic renewable technologies, particularly those which see a majority deployment in the distribution network, such as photovoltaics.

Ongoing research on transmission system connected storage has identified the possibility of extending such techniques to the power distribution network. The goal of this work is to solve the grid operational problems posed by distributed renewable generation as close as possible to their source. With the development and future deployment of domestic scale battery storage at consumer premises, there will soon be a resource available, which without proper research will either be underutilised or utilised in a manner that is not grid empathetic. This project will investigate the potential for distributed energy storage to contribute to grid operation. This will consider both their ability to assist at local distribution level as well as supporting the whole power system in an aggregated manner.

The project objectives are:

Constraint reduction: Exploring methods of local energy balancing, power flow optimisation and power quality regulation to reduce the need for constraint of renewable generation ( or indeed constraint of emerging loads such as EV charging) in the distribution network.

Curtailment reduction: Development of system-wide services which can be implemented by an aggregated virtual power plant of distributed storage, such as fast-frequency response, synthetic inertia and reserve. These services should increase the SNSP capability of the whole power system, thereby reducing curtailment.

Practical implementation considerations: Any trade-off between local and system-wide services will need to be considered. Payment mechanisms for existing and new ancillary services will be explored, with proposals made for the development of future ancillary services which are unlikely to be possible without distributed energy storage.

The majority of the work will be simulation-based using suitable power system models with software such as Matlab and DigSilent. However, incorporating practical engineering aspects is an integral part of the project. This will be achieved using in-house renewable resources, field data measured throughout Northern Ireland and via engagement with industrial and utility partners.