The NIC-funded Distributed ReStart project aims to provide a world first by coordinating distributed energy resources (DER) to provide a safe and stable Black Start service in the event of system-wide blackout.
It’s a bold ambition which departs from traditional reliance on contracts with large power stations to provide Black Start services. And, therefore, it could also be a game changer for the net zero agenda, breaking down one of the final bastions of our dependence on centralised fossil fuel generation.
The three-year Distributed ReStart project is founded on a collaboration between National Grid ESO, Scottish Power Energy Networks (SPEN) and specialist energy consultancy TNEI. In December 2019, the project team filed its first progress report – a positive document which reported “no unsurmountable barriers” had been identified during proof of concept for its innovative new approach to Black Start and which announced the scheme would forge ahead with live trials in 2020.
Speaking to Network, Distributed ReStart project lead and data and modelling manager at National Grid ESO, Peter Chandler sheds more light on these trials and the issues they must overcome to keep moving the project forward.
Three sites have already been identified for running a multiplicity of tests and Chandler explains that these were carefully selected in order to include a broad range of network characteristics and generation technologies. While initial trials will be relatively basic, Chandler keenly anticipates a build up towards some “quite sophisticated” Black Start drills in summer 2021.
“June, July time will be the first initial stage of restoration where we will test a generator by applying blocks of demand,” says Chandler. “We will load it up to stable load, which is as far as we will go for this initial set of live trials but, as we progress through the next 15 months, we’ll undertake various stages of the restoration process, all the way from the initialisation and loading of that generator, through to energising part of the distribution network and linking in some asynchronous technologies further down the chain, such as wind farms and batteries.”
Trials and tribulations
The first live trials for Distributed ReStart will take place at three sites across SPEN’s networks – in both Scotland and the North West of England where it owns the Manweb network. The sites, located in varying geographies, offer the opportunity to trial how a distributed approach to Black Start would work using a range of DERs and other relevant technologies.
Two of the sites are in Scotland and one in the North West. The first planned case study will test how an embedded biomass generator responds to the rigours of Black Start while the following trials will use hydro generation and gas plant.
“We’ve got options for these case studies to reach out to the distribution networks to connect some of the asynchronous generation,” says Chandler. “So, not just the initial self-starting generator technologies – the secondary generators as well. The three case studies we’ve chosen will utilise a wide diversity of different tech to test out our theories about how distributed Black Start will work in as many practical ways as possible.”
Getting to the point of running the tests has presented its own hurdles for the project team – from legal challenges to technical ones. But Chandler is now confident their tests will be able to operate robustly within the constraints they’re facing – when considering the different types of energy generation they will be working with, and also the types of operations they will be putting the generators through, which will almost certainly exceed the design parameters of the equipment involved.
“One of the main challenges is that with biomass and gas generation, for example, there’s emissions legislation that we have to adhere to consistently – and the generators are not designed to be tested this way,” says Chandler. “So, there’s liaison with the Environment Agency and Natural Resources Wales etc., to keep them in the loop and make sure we stay on the right side of the law, with regard to those potential emissions from pushing the generators.
Other pivotal challenges for Chandler’s team will include overcoming the types of problems presented by the generally less-stable network environment of the small distribution power islands created in the trials – such as inertia challenges, voltage challenges and managing system frequency – so the ability of the team to stabilise the power islands will be key. This has led Chandler’s team to issue a tender out to energy technology providers to design an automated control system in order to allow for optimal operation of the generators.
“The theory is that loading this generator, ap- plying large blocks of demand, is very onerous on the generator and might cause it to trip or damage. So, we want to be doing this in as smooth a way as possi- ble and the best way to do that is through automation. Our ‘micro grid control system’ tender has provided the opportunity for a number of companies to go away and design control systems in order to do that.”
Once a successful design has been put forward and awarded a contract, the project team will push forward with the build of a physical system which can be tested as a part of these live trials. “In regards to that, the initial live trials will be fairly manual type trials and fairly basic – but ramping them up, with the control system, that’ll be like the final piece of the jigsaw that we can start testing.”
Bringing DERs in from the cold
One of the major challenges in making distributed Black Start a reality is overcoming the problem of cold starting remote generation assets.
“When the grid goes down, there’s no power for the generator to effectively self-start, so it needs its own power supply on site – a backup generator to effectively jumpstart that main unit,” explains Chandler. “That could be a big battery or a diesel generator. With the live trials we’re going to be hiring in some of the equipment necessary to carry out the restarts – backup generators – to act as auxiliary power supplies.”
Chandler and his team have also been challenged within the scope of the Black Start project to explore the use of both synchronous and non-synchronous self-starting generators in the restoration process.
Chandler believes both are viable. “A generator wouldn’t necessarily need to be synchronous – I think certainly the conventional methods of self-starting generators assume a synchronous generator, the reason being that synchronous can regulate frequency, regulate voltage, and can effectively apply block loads and operate in a number of different modes that are needed. “There are asynchronous generation technologies out there that can potentially operate in a self-starting generator mode, but we’ve got none of those on the system at the moment, but we will be doing a piece of work around this involving our academic stakeholders.
“A German project proved the concept and utilised a battery for asynchronous self-start capability on a gas generator, and at present we’ve had some companies come back to us and say ‘our converter could be made to offer grid-forming capability, effectively making it a self-starting generator’, but we will not be testing these in our live trials as yet.”
To date there have been numerous trials around the world, testing many of the individual elements involved in the Black Start chain, but no one has actually brought all of them together into a coordinated, holistic project, which is what makes the Distributed Restart Project “so cool”, says Chandler.
“We’re actually looking at a full-on restoration service at distribution level, bolting all these innovative ideas and projects together. What we’re trying to achieve has not been done before, so I genuinely believe it’s a world first!”
Commercial and transition agendas
In terms of the commercial and procurement elements of the project, there is a lot of interest from flexible demand companies and DERs wanting to participate, with an eye to commercial benefit from the provision of Black Start services.
Chandler and his team have now compiled options for the procurement and design of services, so clarity is growing as to what these commercial models might entail – an essential development if distributed Black Start is ever to take up the mantle of mainstream grid backup.
Part of the work has also en- tailed consideration of potential clashes between Black Start contracts and the activities that the same DERs might be providing to current and future Distribution System Operators (DSOs).
“We’re at a point now where we’re taking those ideas out and sharing them with all the stakeholders, giving them the opportunity to comment, feedback and hopefully shape new markets,” says Chandler.
“And yes, there is potential for clash with the DSO agenda, but we’re mitigating that through our engagement with ENA networks. This whole transition to DSOs is still ongoing, so we are working with them to make sure what we propose for our Black Start DER solutions actually aligns with what they’re doing.”
Chandler continues: “The direction of transition seems to be where a DSO can procure its own balancing services – voltage, frequency and inertia control products – and then the ESO can procure its own, also. There’s already a whole host of services that the ESO currently procures and contracts with providers, so all of that will start to be opened out to play as well.”
As this increasingly crowded landscape of flexibility and reliability services develops at a distribution and transmission level, Chandler is firm that central coordination of services and prioritised availability of contracted parties will be key – and in this he sees a major ongoing responsibility for the ESO.
As trials for Distributed Restart move forward, we will see just how tricky a task this may be.
This article first appeared in Network magazine, which has now been incorporated into Utility Week