Woodward 505 (8200‑1302) Controller PID Complete Tuning Guide

Application: Steam Turbine Speed Governing & 505 Controller Field Commissioning

Woodward 505 model 8200‑1302 is the most widely used digital governor controller for industrial steam turbines. Many field engineers get confused during commissioning: this controller does not adopt the traditional independent P‑I‑D parameter structure. It uses a special algorithm with PGAIN (Proportional Gain), IGAIN (Integral Gain) and SDR (Derivative Ratio). Directly applying conventional PID logic will easily lead to speed oscillation, valve actuator chattering and slow response.

This document covers Woodward official principles of the 505 speed/load main PID, standardized field tuning workflow, reference parameter values, troubleshooting of abnormal phenomena and usage of auto-tuning tools. It can be used as a reference manual for field commissioning.

Safety Statement: Steam turbines are high-risk rotating equipment. Modification of PID parameters must be performed by certified field engineers. Before changing parameters, confirm the control valve is free from sticking and the unit operates under stable conditions. Adjust parameters in small increments and record trend curves throughout the process.

1. PID Parameter Description for 8200‑1302 (Woodward 505)

The derivative term of the 505 controller is not set independently. The derivative effect = IGAIN × SDR. SDR is called Derivative Ratio with an adjustable range of 0.01‑100.

• PGAIN (Proportional Gain): Proportional action, determines the response strength of the control system. Higher PGAIN delivers faster regulation response; excessive value causes continuous speed oscillation. Too low PGAIN results in sluggish regulation and static speed deviation.
• IGAIN (Integral Gain): Integral action, used to eliminate steady-state speed deviation. Higher IGAIN means faster integral action. Excessive IGAIN easily triggers overshoot and cyclic swing. Too low IGAIN requires a long time to remove static error.
• SDR (Derivative Ratio): Controls the strength of derivative action.
  SDR=100: Derivative function fully disabled, recommended for most steam turbine sites.
  Lower SDR brings stronger derivative action which suppresses step overshoot. However, if SDR is set too low and noise exists on the speed tooth wheel signal, high-frequency valve chattering will occur directly.

Important Note: The 505 controller contains multiple PID loops: speed/load main PID, auxiliary PID and cascade PID. All content below applies to the speed-load main PID only. Other loops require separate parameter tuning.

2. Standard Field PID Tuning Procedure

Official standard tuning logic: Disable integral and derivative first; tune proportional gain; then enable integral; enable derivative only when necessary. Never activate all parameters for tuning at the beginning.

• 2.1 Pre-commissioning Preparation
  Enter Service mode, open the speed PID dynamic parameter screen and enable controller trend recording to capture three curves: speed, valve position and setpoint.
  Ensure stable unit operation, no mechanical limit on the control valve and no valve sticking. Mechanical faults must be resolved first; PID parameters cannot fix mechanical problems.
  Parameter initialization:
  SDR set to 100 (derivative disabled)
  IGAIN set to 0.01 (integral nearly disabled)
  At this point the controller works as an approximate pure proportional regulator with only PGAIN active.
• 2.2 Tune Proportional Gain PGAIN
  Switch the controller to automatic mode and perform small step test: change speed setpoint slightly by 20‑50rpm, observe response curves of speed and valve position.
  Increase PGAIN in small steps (20‑30% increment each time), repeat step test after each modification.
  When slight continuous speed oscillation appears, PGAIN reaches its limit. Roll back to the previous non-oscillating value as the suitable proportional gain.
  Phenomenon judgment:
  Too small PGAIN: slow speed response after step change with obvious static deviation.
  Appropriate PGAIN: fast response without continuous oscillation, static deviation exists (normal when integral is not enabled).
• 2.3 Tune Integral Gain IGAIN
  Keep PGAIN fixed and SDR remains at 100 with derivative disabled.
  Increase IGAIN gradually with small adjustments, perform step test after each change.
  Static speed deviation will be eliminated as IGAIN rises. If overshoot and cyclic swing occur after continuous increase of IGAIN, reduce IGAIN to the value just free of oscillation.
  Phenomenon judgment:
  Excessive IGAIN: speed repeatedly surges and oscillates after load disturbance.
  Too low IGAIN: static deviation takes extremely long time to be eliminated.
• 2.4 Tune Derivative Ratio SDR (Optional, derivative can be disabled for most units)
  Derivative tuning is only required when P & I parameters are fully tuned and large step overshoot exists without system oscillation. Most steam turbine sites can operate stably with SDR=100 (derivative off).
  Start with SDR=100 and reduce SDR gradually (lower SDR = stronger derivative). Modify in small increments.
  Observe step response: reduced overshoot indicates derivative works. If high-frequency minor speed fluctuation occurs, increase SDR immediately to weaken derivative action.
  Critical pitfall avoidance: Do NOT enable derivative when noise exists on speed probe or tooth wheel feedback. Derivative amplifies noise and causes frequent valve chattering.

3. Factory Default Reference Parameters (Only as startup baseline, must be tuned on-site, cannot be copied directly)

For small turbines with low rotor inertia, take the lower bound of PGAIN range.
For large turbines with high inertia, PGAIN can be increased moderately.

4. Instructions for Built-in Automated PID Optimizer of 505

Woodward 505 is equipped with Automated PID Dynamic Optimizer. The controller automatically applies step disturbance and calculates P/I/D parameter values.

Precautions: The unit must run under stable conditions with no valve sticking. Confirm the process permits temporary disturbance before starting auto-tuning.
Parameters generated by auto-optimization serve only as reference. Engineers must manually verify and fine-tune parameters by step test afterward; auto-tuned values cannot be directly adopted for long-term operation.

5. Common Fault Phenomena & Parameter Handling Solutions

6. Tuning Summary

The PID logic of Woodward 505‑8200‑1302 differs from conventional PID. Its derivative term depends on integral gain, and SDR (Derivative Ratio) is the most error-prone point. Derivative is recommended to stay disabled in most cases.

Follow the tuning sequence strictly: P first, then I, D only when required. Adjust parameters in small increments and judge performance by step test and trend curves.

PID parameters only optimize closed-loop control performance. Hardware issues such as valve mechanical sticking and signal faults cannot be fixed by modifying PID settings.

After PID tuning, besides small step tests, load increase/decrease disturbance tests must be performed to verify speed regulation quality under variable operating conditions.