Superheater and Reheater Desuperheating Water Control with Partial Smith Predictive Correction

The desuperheating water control is critical to steam temperature regulation for most coal-fired units in response to rapid peak shaving and frequency modulation. The classic cascade control performance is difficult to meet the requirements of its large inertia and large delay. The practical application of algorithms such as model predictive control and neural network control is also greatly limited due to its nonlinearity, measurement uncertainty and time-varying characteristics. The system is modeled in two parts, where the main inertia and delay subsystems are easier to obtain accurate models. Then a partial Smith predictive correction method was proposed to be combined with classic cascade PID controller. The applications in a 600 MW supercritical boiler and a 1000 MW ultra-supercritical boiler had demonstrated a more stable and efficient performance than the classic cascade control, and it is simple and much easy to use.