Microgrids for uninterruptable power supply systems (UPS) have been used in high-value service provider buildings for many years. Despite they use conventional network topologies with relatively conventional control and protection systems, the use of low voltage DC to supply information technologies (IT) loads is rapidly becoming standard. In these systems, DC is is seen as an opportunity to improve reliability and to reduce energy losses and costs. Today the market of photovoltaics, batteries, power electronics and IT hardware keeps growing as these technologies become more cost-competitive. Thus, the use of DC could be extended to further types of loads, generation and storage giving rise to hybrid AC-DC microgrids. When considering the current business-as-usual approach to electrical network design, planning and operation, the growth of renewables and power electronics is often seen as a threat to electrical networks. However, by exploiting the controllability of power electronics it would be possible to build highly-reliable, energy-efficient and cost-effective networks with low carbon impact. High-value buildings today present interesting opportunities to test new concepts of microgrids that could be used at a larger scale in the future. However, multiple technical questions still remain unanswered, such as: "how much can microgrid design be optimised while preserving high reliability?" or "how does low level control for transient stability affect battery life span and how can it be improved?" to name a few. This project seeks to answer these questions by bringing together world leading expertise on microgrids, network planning, energy storage, power converter design and power electronic control from the UK and Korea. The project will consider hybrid AC-DC microgrids with loads, generation and energy storage connected in either side. It will focus on applications to high-value service provider buildings with the ambition of generating knowledge that will be useful in other applications and at greater distribution network scale.

Potential Impact:
Around the world there is a growing emphasis on the resilience and security of energy supply being addressed at local level to a greater extent and in preference to achieving this through measures only at the national scale electricity system. A common expression of this is the micro-grid. Microgirds aid resilience through the ability to manage critical loads and supply them as first priority from local resources, the resources being local generation supplemented by local energy storage. Further, a mircogrid can use its resources of generation, storage and dispatchable load offer control and support services to neighbouring microgrids and to the larger grid beyond. Establishing the cost-benefit case for providing resilience in this fashion will have impact on approaches to planning networks that could yield substantial cost savings.

A hybrid AC + DC microgird offers a transition to new forms of energy distribution in buildings. The DC element could, when established, yield cost savings in integrating roof and façade PV and battery energy storage and in interfacing IT and lightning loads in offices and homes. The hybridisation with an AC element allows traditional equipment and high power equipment to be accommodated readily. Demonstrating the feasibility and efficacy of the hybrid approach will have impact on the design of building services.

A key element of the hybrid microgrid is the multi-port power converter at its hub. By working closely with power electronics manufacturers we aim to be able to provide a ready route to commercialise such a technology.