Short Answer:

The purpose of an Automatic Generation Control (AGC) system is to automatically control the power output of multiple generators in a power system to keep the system frequency stable and maintain the power exchange between areas at scheduled values. AGC ensures a balance between total power generation and load demand in real time.

It plays a critical role in maintaining system stability, frequency regulation, and economic dispatch by continuously adjusting generator outputs based on real-time measurements. Without AGC, power systems would experience frequent frequency deviations and instability during load changes.

Detailed Explanation:

Purpose of automatic generation control system

An Automatic Generation Control (AGC) system is a vital part of modern power system operation and control. Its main function is to maintain the balance between power generation and consumption on a real-time basis by automatically adjusting the output of generators. This helps in keeping the system frequency at its nominal value (e.g., 50 Hz in India) and ensures that the interchange of power between different control areas remains at planned levels.

In interconnected power systems, sudden changes in load demand can cause frequency to deviate. AGC responds to these changes automatically and brings the frequency back to normal without manual intervention. It also helps coordinate power sharing among generators and regions to achieve stability and economic efficiency.

Key Functions of AGC:

1. Frequency Regulation:
   AGC monitors the system frequency continuously. If the frequency drops (indicating more demand than generation), it increases the output of generators. If frequency rises (indicating more generation than demand), it reduces generation accordingly.
2. Tie-Line Power Flow Control:
   In multi-area power systems, AGC ensures that the power exchanged between different areas remains close to the scheduled values. This avoids overloading of tie-lines and keeps regional systems operating fairly and reliably.
3. Load-Following Capability:
   AGC adjusts generation to match changes in load demand throughout the day, ensuring smooth operation of the power system.
4. Economic Operation:
   By distributing load among generators based on their cost characteristics and system needs, AGC supports optimal operation and cost reduction.
5. Automation and Speed:
   AGC provides rapid response compared to manual control. It reacts within seconds to balance supply and demand, improving the dynamic performance of the grid.

Components Involved in AGC:

• Control Center: Receives real-time data from power plants and tie-lines.
• Area Control Error (ACE): The difference between actual and scheduled power (considering frequency deviation), used to guide AGC action.
• Load Frequency Controller (LFC): Subsystem within AGC that adjusts generator setpoints to correct frequency.
• Governor and Turbine System: Adjusts mechanical input to the generator based on AGC commands.

Benefits of Using AGC:

• Maintains stable frequency during sudden load changes.
• Enhances coordination among different power generation units and areas.
• Minimizes the need for manual control by system operators.
• Reduces wear and tear on equipment due to frequent load changes.
• Improves power quality and system reliability.

Conclusion:

The purpose of an Automatic Generation Control (AGC) system is to automatically balance power generation and demand, regulate system frequency, and maintain scheduled power interchange among regions. AGC is essential for modern interconnected grids, ensuring stability, reliability, and economic efficiency in real-time power system operation.