How do you design anti-surge control for centrifugal compressors?

Anti-surge control prevents compressor operation beyond surge line (minimum flow limit). Design elements: surge detection (distance to surge from operating point), surge control line (safety margin below surge line, typically 10%), recycle valve sizing (pass surge flow at trip conditions), fast-acting control loop (high gain, minimal dead time), hot bypass or cold recycle selection, and integration with load/performance control. Implementation: PID with derivative for fast response, specialized anti-surge controllers with adaptive algorithms, measurement validation (suction/discharge pressure, temperature, flow). Include post-surge recovery logic and coordinate with ESD system.