What is integral windup and how is it prevented?

Integral windup occurs when the controller output saturates (at 0% or 100%) but the integral term continues accumulating error, causing excessive overshoot when the output returns to normal range. Prevention methods: external reset (integral tracks actual valve position), conditional integration (disable integral when output saturated), back-calculation (reduce integral based on saturation), and velocity form algorithm. Modern controllers include anti-windup protection that must be properly configured for cascade, override, and split-range applications.