Automatic generation control (AGC) is a vital function of power system operation and control. It ensures the balance between the generation and the load demand, as well as the frequency and the tie-line power interchange with other systems. In this article, you will learn about the main components and functions of an AGC system.
The main objective of AGC is to maintain the system frequency and the tie-line power interchange at their scheduled values. This is achieved by adjusting the output of the generating units according to the changes in the load demand and the system conditions. AGC also coordinates the economic dispatch of the generating units, which means allocating the load demand among the available units in the most cost-effective way.
An AGC system consists of four main components: the control center, the communication network, the local controllers, and the generating units. The control center is the central authority that monitors and controls the system frequency and the tie-line power interchange. It receives the data from the local controllers and sends the control signals to them. The communication network is the medium that connects the control center and the local controllers. It can be wired or wireless, depending on the system configuration. The local controllers are the devices that receive the control signals from the control center and regulate the output of the generating units. They can be governors, exciters, or power electronic converters, depending on the type of the generating units. The generating units are the sources of electrical power in the system. They can be thermal, hydro, nuclear, wind, solar, or other renewable or non-renewable units.
An AGC system performs two main functions: load frequency control (LFC) and economic dispatch (ED). LFC is the function that regulates the system frequency and the tie-line power interchange by adjusting the output of the generating units. It is usually divided into primary, secondary, and tertiary control levels. Primary control is the fastest and most basic level of LFC. It is performed by the governors of the generating units, which respond to the frequency deviations by changing the mechanical power input. Secondary control is the next level of LFC. It is performed by the control center, which sends control signals to the local controllers to correct the frequency deviations and restore the tie-line power interchange to their scheduled values. Tertiary control is the highest level of LFC. It is also performed by the control center, which reschedules the output of the generating units to optimize the system operation and minimize the fuel cost. ED is the function that allocates the load demand among the available generating units in the most cost-effective way. It is performed by the control center, which calculates the optimal output of each unit based on their operating costs and constraints. ED can be integrated with LFC or performed separately, depending on the system design and requirements.
An AGC system faces several challenges in its operation and control, such as the uncertainty and variability of the load demand and renewable generation, which necessitates more flexibility and robustness. Additionally, it must be able to interconnect and coordinate multiple systems, requiring more communication and cooperation among the control centers and local controllers. Cyber-security and reliability of the communication network is also a concern, requiring more protection and redundancy from the AGC system. Finally, there are environmental and social impacts of the generation mix that necessitate more sustainability and efficiency from the AGC system.
With increasing renewable penetration, balancing demand and generation for maintaining frequency and voltage via Automatic Generation Control (AGC) becomes challenging due to the uncontrollable nature of solar and wind energy. Combining AGC with automatic load control through demand response or integrating green hydrogen energy storage offers viable solutions. Additionally, AI-driven load and generation forecasting enhances grid stability by predicting fluctuations, enabling better management of renewable variability and ensuring a reliable, sustainable energy supply.
To overcome the challenges associated with AGC systems, it’s important to integrate advanced technologies and methods such as artificial intelligence, machine learning, smart grid, demand response, and energy storage. This can improve the accuracy, speed, and adaptability of the system. Additionally, developing new standards and protocols like IEEE 1547, IEC 61850, and IEC 61400 can facilitate interoperability and compatibility. Implementing new policies and regulations like market-based mechanisms, incentives, and penalties can also motivate participation and contribution. Finally, educating stakeholders and customers about the AGC system increases understanding and acceptance.
Cybersecurity at AGC is crucial as the communication infrastructure is vulnerable to cyber attack. Even with the advancement in the data driven technologies like artificial intelligence, machine learning, and deep learning, there is a possibility of adversarial attacks which may mislead the data driven tools for mal operation and may bypass the highly discriminative false data detector.