Adaptive Optimal Control of Steam Temperatures for Thermal Power Plants

This paper describes a new adaptive optimal control method for boiler steam temperature control of thermal power plants. Fig. 1 shows a schematic diagram of the adaptive optimal control system. A coal-fired power plant and the automatic plant control (APC) system are assumed to be a single controlled object in order to allow the APC to continue controlling the power plant, even if the adaptive optimal control system fails. A process dynamics model, composed of the above mentioned controlled object and a disturbance source, is proposed. The process dynamics model is represented by a multi-input and output autoregressive moving average (ARMA) model to predict future trends in process behavior. The disturbance source is the central load dispatching office. Parameters of the process dynamics model are identified during high and low load level power plant operation on a real-time basis when load fluctuations are relatively small. Optimal controller gains are calculated using the identified model by the dynamic programming (DP) method and adapted on-line when process characteristics change as a result of changing fuel heating value or during the course of long-term operation. These control gains suppress fluctuations in both main and reheater steam temperatures.