When frequency is low, what should the ACE value preferably be for a favorable CPS1 score?

When frequency drops below the desired level in a power system, it often necessitates an increase in generation or a decrease in demand to restore balance. The Area Control Error (ACE) reflects the difference between actual and scheduled generation while also considering the effects of frequency on the system.

A positive ACE value indicates that the actual generation is less than the scheduled generation, which signifies that there is not enough generation to meet demand at that frequency. This can negatively impact the system's performance metrics, such as CPS1 (Control Performance Standard 1), which measures the effectiveness of frequency control.

When the ACE is positive in a low-frequency scenario, it suggests that as generation is increased, it can help improve the frequency back to its desired level. Thus, maintaining a favorable CPS1 score is facilitated by ensuring that ACE remains positive when frequency is low. A positive ACE indicates that balancing actions are being appropriately applied to correct the frequency deviation.

In this context, a negative ACE would imply oversupply, which is not needed when frequency is low, while a zero ACE indicates that the system is in balance but may not effectively address the existing frequency issue. Therefore, focusing on maintaining a positive ACE value is essential during periods of low frequency to ensure that corrective actions are taken to