In this sponsored post Jon Downs, director – grid integration UK & Ireland for ABB’s Power Grid Division explains how innovative technology is reshaping the grid to meet the challenges created by the UK’s fast changing energy mix.
There have been considerable discussions about how reducing the UK’s dependency on fossil fuels will require our power systems to adapt and become more flexible. However, a series of important and interlinked developments in recent months have shown that the changes are happening right now, and the momentum is building at an ever increasing rate.
The energy system landscape has reached a turning point as renewables plays an ever increasing part of our energy mix, alongside the accelerated decline of coal generation. For the first time in more than a century, UK electricity production has been coal free and recently demand-side balancing has used to provide much needed flexibility to the grid. With these changing times comes both new challenges and new opportunities.
Innovation and entrepreneurship are rising to the challenges of a changing energy system. National Grid has been seeking new services to support system balancing and operation in response to declining generation margins and eroding system inertia. We are also seeing major industrial and commercial consumers using technology to secure supplies by creating their own off-grid power solutions. For example, Sainsbury’s, who consume just under one percent of the UK’s power output, is building a string of gas-fired power plants for its supermarkets, with 10 already in operation and a further six planned for this year. This autonomy will enable the stores to keep trading even in the event of a blackout while also producing heat.
The UK grid is clearly facing a challenging time. However, there are grounds for optimism. Solutions are at hand in the form of ABB’s portfolio of innovative connection technologies developed to control power flows, support network stability and improve availability.
Fast fault current limiting
DNOs (Distribution Network Operators) need to adapt their network assets to handle the fault current challenges created by connecting increasing levels of low carbon generation. Normal substation circuit-breakers cannot provide protection against fault currents, as they are too slow to respond. In contrast, ABB’s Is-limiter can detect and limit a fault current at its first rise – in less than a millisecond – this ensures that the maximum instantaneous current is limited to a safe level that will not cause damage to the substation equipment.
The Is-limiter is already a tried and tested technology, with over 600 reference applications worldwide. It is now being deployed in trial installations in the UK to demonstrate its potential to improve network performance, boost connection capacity and help improve customer satisfaction, without the need for multi-million pound investments in new substation infrastructure.
Energy storage for frequency stability
Renewable power sources cannot offer spinning inertia of the kind provided by traditional turbine-based power generation. Hence there is a growing risk of frequency instability. Paradoxically, the greatest challenge could come during a warm summer night – when demand is low and therefore the system base load generation is low – so that a small system disturbance, resulting typically from something such as a severe lighting storm, could cause a catastrophic and very rapid drop in frequency.
A particular advantage of a grid-connected battery energy storage system (BESS) is that it can deliver very fast sub-second response to support grid frequency until additional generation assets, short term operating reserves and/or more hydroelectric power can be brought on stream and synchronised to the grid.
ABB has expertise in integrating grid-scale BESS solutions. Large-scale batteries of the right capacity are available from several suppliers, based on a number of different technologies. But to meet the performance and reliability needs of grid operators – especially in frequency response services – these batteries need to be integrated with the right power control systems, power converters, switchgear, transformers and overall management system.
While frequency response services are the most significant UK application currently, ABB has delivered other BESS solutions such as time-shifting of wind and solar power, capacity firming, load levelling, peak shaving, power quality control and stabilisation.
Back to back medium voltage direct current links
ABB’s ground-breaking medium voltage direct current technology enables the connection of previously incompatible distribution networks as well as helping to manage voltage levels. Based on back-to-back power electronic converters, medium voltage direct current links allow the controlled transfer of both real and reactive power flows between two network sections. Such connections have not been possible until now because of issues with circulating currents, protection grading or fault level constraints.
The capability for power transfers across two separate distribution grid groups can help balance generation and demand locally, while also unlocking additional capacity under both normal and abnormal network conditions. This can be achieved quicker and at significantly lower financial and environmental cost than the traditional reinforcement method of building new connections from each distribution grid back to the nearest substation. It is estimated that deploying such medium voltage direct current links across the UK would alone release 1.5 GW of capacity by 2050.
Transportable compact substations
For customers who require a substation to fit within a compact footprint or delivered within a fast time-scale to enable the grid connection of new renewable energy assets, ABB has developed customized, factory assembled substation equipment for permanent or temporary installations. These MFMS (Multi-Function Modules) combine in a single product the following functions: High-voltage switchgear; Power transformer; Medium-voltage switchgear; Control and protection.
Microgrids – the time has come
Microgrids combine a range of generation sources with energy storage and intelligent load management to provide reliable, economic and environmentally friendly power supplies. They can also be used as black start power or to bolster the grid during periods of heavy demand, especially in providing vital ancillary services such as frequency support.
Grid-connected microgrids can be seamlessly ‘islanded’ from the main grid when needed, for example during periods of peak power grid usage, or during a primary power grid failure. In this mode, the microgrid isolates its local generation and loads from a faulty grid and operates independently for prolonged periods.
The system is controlled through a microgrid control system, such as ABB’s Microgrid Plus System, that can incorporate demand–response so that demand can be matched to available supply in the safest and optimal way. A flywheel- or battery-based grid stabilising system like ABB’s PowerStore may be included to offer real and reactive power support. The microgrid control system provides dynamic control across all the various energy sources, enabling autonomous and automatic self-healing operations.
Integrated ‘fly by wire’ solutions
These technologies offer the most benefit when integrated as part of an over-arching scheme with ABB’s sophisticated control and software solutions – creating what is effectively a ‘fly by wire’ concept. This approach will enable DNOs to plan complex networks more effectively for low-carbon technologies, optimise voltages and power flows to utilise the existing electricity network fully, and balance generation and demand more efficiently – all while increasing the resilience of networks and securing electricity supplies for customers.