Energy, often dubbed the lifeblood of modern civilization, is the driving force behind the technological advancements and economic growth we witness today. In particular, electricity is the backbone of our society, powering our homes, industries, and economies. Without a reliable and secure supply of energy, development and progress would come to a grinding halt. As the world’s energy demand continues to surge at a pace faster than the growth of its population, ensuring that everyone has access to a secure, safe, and continuous energy supply is now at the forefront of numerous research projects worldwide. The linchpin of many such endeavors is energy efficiency, and it remains a primary goal for both energy supply companies and consumers due to its far-reaching financial and security implications.
In the quest for a more resilient and efficient energy ecosystem, various support schemes have emerged. These schemes, such as Demand Side Management (DSM), generation and consumption flexibility, sector coupling (electrification of mobility and heating), and Ancillary Services (AS), play a pivotal role. Among these, Ancillary Services, also known as AS, hold a special place. These services encompass actions and functions that aid electricity transmission and distribution system operators in maintaining a reliable and secure electricity supply. In essence, AS serves as the safety net, ensuring the operation of power grids within specified security and delivery parameters. These services are typically provided by third parties or by the system operators working at different voltage levels within the grid.
One of the driving forces behind the growing need for Ancillary Services is the increasing share of Renewable Energy Sources (RES) in the global power supply. Projections from organizations like the Intergovernmental Panel on Climate Change (IPCC) indicate that renewable energy sources could make up as much as 88% of the energy mix by 2050. Notably, photovoltaics and wind power have taken center stage in the installation of new capacity. However, the rise of these intermittent energy sources brings the challenge of maintaining a stable power grid. This is where Distributed Energy Sources (DER) and Distributed Renewable Energy Sources (DRES) enter the picture. These sources, when aggregated and efficiently managed, have the potential to offer a competitive advantage by addressing issues closer to the point of generation and consumption.
The core task of Transmission System Operators (TSOs) is to ensure the stability of the power grid, accomplished through close monitoring and the utilization of various Ancillary Services. Today, many of the AS in use focus on frequency and voltage control to a certain extent. Yet, with the growing penetration of DRES into distribution power grids, technical complexities emerge in various grid elements. To address these issues, diverse Ancillary Services become necessary.
The global landscape of energy is evolving at an unprecedented rate. As conventional power generation sources are gradually replaced, we anticipate more frequent grid disturbances. This transformation will bring about not only technical challenges but also economic and regulatory changes. These adjustments are crucial for enabling the reliable operation of the grid under new constraints.
In this landscape, the European power grids and energy markets offer valuable insights. These systems are mature, well-coordinated, and constantly evolving, making them a rich source of information for further investigations. The increasing prevalence of renewable energy in the energy mix has implications for power generation security. The inherent variability of solar and wind sources, which have seen remarkable growth in the past decade, poses a potential threat to a secure and continuous power supply. As a result, there is a growing need for reserve capacity, which can be activated when faults occur due to insufficient power feed-in into the grid, especially when demand exceeds supply.
Ancillary Services, by definition, are services that ensure the smooth operation of the power supply within acceptable limits. They can be offered by third parties or by the system operators themselves, such as Transmission System Operators (TSO) and Distribution System Operators (DSO). The nature of these services can vary depending on the type of power grid and the regulations governing power trading mechanisms. For instance, microgrids require different services compared to the transmission system due to differences in voltage levels.
For the European Network of Transmission System Operators for Electricity (ENTSOE), a cooperative organization of European transmission system operators, AS are classified under three “umbrella terms”:
- Frequency AS: These services focus on balancing the demand and supply to prevent frequency deviations.
- Services for Congestion Management: These services help manage congestion within the power grid.
- Non-Frequency AS: This category includes voltage control (involving reactive power compensation) and grid restoration (enabling the recovery of parts of the grid after a blackout).
Frequency control
Frequency control is at the core of a robust power supply chain. It encompasses several services designed to maintain the equilibrium between power generation and consumption, particularly during disturbances. The following key services are vital in this regard:
- Frequency Containment Reserve acting swiftly, responding to positive or negative deviations within just 30 seconds.
- Secondary Frequency Regulation includes two main services, automatic Frequency Restoration Reserve (aFRR) and manual Frequency Restoration Reserve (mFRR). aFRR springs into action within 30 seconds of a deviation and aims to restore the desired frequency.
- Replacement Reserve (RR): RR comes into play for tertiary frequency regulation. It stands ready to address additional imbalances, ensuring the continued stability of the power supply.
Service for Congestion Management
The power grid is not immune to congestion issues especially as power flows from generation points to consumption points. Congestion typically arises when transmission lines become overloaded, exceeding their carrying capacity, thermal capacity, or power flow limits. It’s important to understand that congestion can manifest in various forms:
- Market Congestion: This occurs when not all trading orders submitted by market participants can be executed, potentially impairing power grid operations.
- Physical Congestion: This type of congestion is related to power flow issues, specifically regarding the power grid’s elements and their functioning within the grid.
- Structural Congestion: This form of congestion stems from recurring events under normal operational conditions.
Voltage management and grid restoration
Voltage management and system restoration are pivotal services for ensuring grid stability. Voltage control and reactive power compensation play a significant role in maintaining the stability of the electrical grid. These services aim to prevent damage to physical equipment and disconnections of generation units.
Reactive power, generated by rotating masses, is essential for creating revolving magnetic fields crucial for power grid operations. Voltage control is achieved through various hierarchical processes, with primary, secondary, and tertiary voltage control responding to deviations over different timeframes. Automatic voltage regulators and static compensators are essential components for providing these services.
System restoration
Also known as grid restoration, involves measures and actions for bringing the power system back to full operation after a significant disturbance, such as a blackout. Black start capabilities, including conventional power, pumped-storage power plants, and hydropower plants, are essential for restarting parts of the grid and restricting faults.
A well-functioning power supply chain will have to rely on a delicate balance of frequency control, congestion management, voltage control, and system restoration. These services work in harmony to ensure that our electrical grid remains stable, even in the face of various challenges and disturbances. As the energy landscape evolves, the significance of these services becomes increasingly pronounced, guaranteeing the reliability of our power supply.
We hope that we could give you an understanding of what a positive energy district is. Stay tuned for our next “What is…?” Article, as it will revolve around the markets of Ancillary Services.
If you have any questions, please don’t hesitate to contact Evyatar Littwitz.
Do you have any wishes regarding future articles in the “What is…?” series? Then let us know in the comments and we’ll do our best to cover the topic.
Your Es-geht! Team