What happens when a control loop has excessive integral action?

Excessive integral action in a control loop can lead to oscillations and instability. Integral action in a control system accumulates the error over time, meaning that it sums past discrepancies between the desired setpoint and the actual process variable. While this can help eliminate steady-state errors, too much integral action can cause the system's response to overshoot the desired value significantly.

When the system overshoots, the controller works to correct this by applying opposing control actions. If the integral term continues to accumulate while the process variable oscillates around the setpoint, the controller reacts too aggressively, causing further overshoot and oscillations. This can create a feedback loop where the system fails to stabilize, leading to oscillatory behavior or even complete instability. Thus, careful tuning of the integral gain is essential to maintain system stability and ensure that the control loop functions correctly without excessive oscillations.