What is the normal and recommended mode of the AGC?

The recommended and normal mode of Automatic Generation Control (AGC) is the tie-line frequency bias. This approach is essential for maintaining system frequency and managing the balance of generation and load across interconnected power systems.

In this mode, the AGC adjusts generation based on the real-time frequency measurements and the flow of power across the tie lines connecting different areas. The goal is to keep the frequency as close to the nominal value as possible while ensuring that the interchange of energy between interconnected systems remains stable. When the frequency deviates from the set point (typically 60Hz), the AGC automatically adjusts generation resources to correct these discrepancies.

This method is preferred because it allows for a more responsive and stable control of power systems, especially during peak loads or unexpected events. It takes into account both the frequency and the flow of power across the grid, ensuring that the system operates efficiently and reliably.