Grid Ancillary Services

Balancing our power system is a challenging feat! Transmission system operators are responsible for ensuring that our power grid operates safely to prevent damage to our electrical devices, critical infrastructure, and vital facilities like hospitals. As consumers, we also play a role in managing our electricity usage. So, how do we keep our power system stable?

As we see a rise in renewable energy sources, fluctuations in the grid become frequent and pronounced. Balancing power generation with consumption becomes more difficult, as we move towards a greener grid, and a new set of services is necessary to meet these demands.

The answer lies in ancillary services, they serve as a crucial safety measure for our power grid. These services help keep our devices powered, our work uninterrupted, and our economy thriving. They also prevent blackouts and other disruptions caused by sudden changes in the grid.

Knowing the importance of the ancillary services, we will learn about their, classification, types, and participation in the market. Keep reading because this information could provide insights into new business ideas and future career paths in the energy sector.

1. What are Ancillary Services?

These are the supporting services beyond simple energy generation and transmission necessary to maintain a reliable and stable electric power grid. They help balance supply and demand in real-time, ensuring voltage and frequency remain within safe operating limits.

If we get more technical, the Electricity Directive 2019/944 defines an ancillary service as a provision necessary for the operation of a transmission or distribution system. This includes frequency and non-frequency ancillary services but does not include congestion management. These balancing services must meet the system’s requirements and ensure the security of the power system under normal and emergency conditions [1].

In other words, ancillary services refer to a range of functions that TSOs contract so that they can guarantee system security. These services can be manually or automatically activated at any time depending on the event and the power system status at a given moment to ensure stability. Ancillary services can be offered by various technologies such as batteries, wind turbines, combined heat and power (CHP) plants, flywheels, and more.

2. Classification

Let’s break it down from the general to the specific definitions. Grid support services can be categorized into two main groups: frequency services and non-frequency services.

• Frequency services: so-called balancing services (BS) that help TSOs maintain the system frequency within a predefined range and comply with the amount and quality of reserves needed, such as frequency containment reserves (FCR), frequency restoration reserves (FRR), and replacement reserves (RR). The control reserve maintains the stability of the electricity grid frequency, which is set at 50 Hz in Europe and 60 Hz in the US. If this is not done, it would hinder the safe operation of the electricity grid and, as a result, put the reliable supply of electricity at risk, causing blackouts.
• Non-frequency services: also known as flexibility services are used by system operators for steady-state voltage control (active and reactive power domains), fast reactive current injections, inertial for local grid stability, short-circuit current, black star capability, and island operation capability [1].

In the next section, I’ve compiled a comprehensive table to help you understand every concept. This table is based on insights from over 10 scientific papers and input from industry experts. So, even if there are new services that we might not have been aware of, you will find all the information you need.

Figure 1. Ancillary services classification.

3. Types of Ancillary Services (Up to date)

The table below outlines widely used ancillary services worldwide. It’s crucial to note that each of these support services serves a distinct purpose, and they are activated either automatically or manually to address specific disruptions in the power system.

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Table 1. Ancillary services definitions, classification, and characteristics [4–6].

Figure 2. Timescale of Ancillary Services.

4. How does AS participate in the market?

Ancillary services can operate in centralized markets when a TSO centrally procures all necessary ancillary services (common in Europe), and in decentralized markets where services are traded between generators, grid operators, and aggregators (more common in the US).

Ancillary services participate in the market when contracted by TSOs to balance the power grid. TSOs have to purchase control reserves from the BSPs in advance. They rely on regulatory guidelines for deciding how much control reserve to put out for tender [2]. DSOs have recently been increasingly involved in the ancillary services necessary to ensure the security of the distribution grids due to the increase of Distributed Energy Resources (DERs). In Europe, the Electricity Directive promotes a more active role for DSOs, establishing that they shall procure the non-frequency ancillary services needed for their systems [3].

The ancillary service markets in Europe involve four main types of stakeholders: National Regulatory Authorities (NRAs), System Operators (SOs), Balance Responsible Parties (BRP), and Balance Service Providers (BSPs).

Support grid services are procured through competitive bidding processes in the balancing market, long-term contracts (bilateral agreements), and mandatory provisions when certain generators must be capable of providing specific services by regulation.

5. Takeaway

In this blog post, we delved into the world of grid ancillary services, exploring their importance in maintaining the stability and reliability of the power grid. We discussed several types of ancillary services, including frequency regulation, voltage control, and reserve capacity, and how they play a crucial role in balancing supply and demand in real-time. Additionally, we examined the participation of different stakeholders, such as grid operators, balance responsible parties, and ancillary service providers, in the ancillary service market. Understanding grid ancillary services is essential for anyone interested in the power market’s functioning and the electricity grid’s stability.

Stay engaged in future releases if you have a passion for the energy sector, renewables, energy storage, and the factors influencing our power grids. Follow me on Medium and receive regular updates, in-depth insights, and a front-row seat to the evolving energy market. ⚡

References

1. European Union, M. “Directive (EU) 2019/944 of the European Parliament and of the Council of 5 June 2019 on common rules for the internal market for electricity and amending Directive 2012/27/EU.” Off. J. Eur. Union 158 (2019): 125–199.
2. Benjamin Blat Belmonte, Panagiotis Mouratidis, Georg Franke, Stephan Rinderknecht, Developments in the cost of grid balancing services and the design of the European balancing market, Energy Reports, Volume 10, 2023, Pages 910–931, ISSN 2352–4847, https://doi.org/10.1016/j.egyr.2023.07.045.
3. G. Rancilio, A. Rossi, D. Falabretti, A. Galliani, M. Merlo, Ancillary services markets in Europe: Evolution and regulatory trade-offs, Renewable and Sustainable Energy Reviews, Volume 154, 2022, 111850, ISSN 1364–0321, https://doi.org/10.1016/j.rser.2021.111850.
4. Kristian Sevdari, Lisa Calearo, Peter Bach Andersen, Mattia Marinelli, Ancillary services and electric vehicles: An overview from charging cluster sand chargers technology perspectives. Renewable and Sustainable Energy Reviews, Volume 167, 2022, 112666, ISSN 1364–0321, https://doi.org/10.1016/j.rser.2022.112666.
5. Jose Barroco, Designing financeable ancillary services revenue contracts in developing economies: Learnings from the Philippines, Energy Policy, Volume 152, 2021, 112218, ISSN 0301–4215, https://doi.org/10.1016/j.enpol.2021.112218.
6. Zeenat Hameed, Seyedmostafa Hashemi, Hans Henrik Ipsen, Chresten Træholt, A business-oriented approach for battery energy storage placement in power systems, Applied Energy, Volume 298, 2021, 117186, ISSN 0306–2619, https://doi.org/10.1016/j.apenergy.2021.117186.