The application of immune genetic algorithm in main steam temperature of PID control of BP network

Investigation on the energy conversion and load control of supercritical circulating fluidized bed boiler units

Main steam temperature regulation is one of the most demanded control loop in modulating control system of thermal power plant. According to the characteristics of main steam temperature, an intelligent control technology has been proposed. To eliminate lag and inertia in main steam temperature regulation process, the intelligent control technology integrates several advanced algorithms. The application effects in several ultra-supercritical thermal power plants prove that the control technology has outstanding robustness and excellent adaptability in both variable load and steady state condition.

Research and Application of Intelligent Control Technology for Main Steam Temperature Regulation in Ultra-Supercritical Thermal Power Plants

The cascade controller of active-disturbance-rejection-controller and PI controller is applied to the steam temperature system of circulating fluidized bed, which has the characters of large time-delay, fast time-varying and various disturbances. A synthesis tuning algorithm which combined the intelligent optimal method NSGA_II and numerical optimal method algorithm is adopted to tune the parameters of controller. In the computer simulation, all parameters of ADRC and PI controller is tuned with 100% load. The least square algorithm is also applied to tuning PI controller. Then plant with PI controller is looked as a generalized object and fitting function is computed. For the fitting function, multi-objective algorithm NSGA_II is applied to tuning ESO. Then NLF is tuned with non-linear least square algorithm - Levenberg-Marqudart algorithm. As the comparison algorithm, PI-PI controller is well tuned with least square algorithm. The simulation with load-varying demonstrated more robustness and the simulation with water-feed disturbance demonstrated more disturbance rejection of ADRC-PI cascade controller.

ADRC with synthesis tuning algorithm for superheating steam temperature of CFBB

Superheating process in thermal power plant is a two-stage series system. In this paper, model predictive control strategy based on prediction error feedforward is proposed for superheating process. In this series system, the prediction error of the former unit is the estimation of unmeasured disturbance that will further affect the subsequent unit. Consequently, this prediction error can be constructed as an external measured feedforward variable for MPC design of the subsequent unit. The model identification method for this external feedforward variable is also presented. Simulation results indicate that the model prediction accuracy of steam temperature has been improved effectively. This method can enhance the control performance of disturbance rejection for the series system.

Model predictive control strategy based on prediction error feedforward for superheating process

Main steam temperature control system in thermal power plant is a system with large time constant, long time-delay, slow time-varying and various of disturbance factors, traditional PID control generally can't satisfy the performance requirement. This paper introduces and analyses the basic theory and properties of Predictive Functional Control(PFC). The algorithm of first-order plus dead-time system is provided particularly. PFC-PID cascade control strategy is given out by combining PFC with PID control, and applied to main steam temperature control system in thermal power plant. Internal loop of the system adopts PID control strategy, and internal loop and the super-heater high temperature plant constitute generalized control plant of PFC. The control algorithm is simple because predictive model of PFC is first-order plus dead-time model which is gained by matching generalized control plant. Furthermore, the system with unmatched model still has favourable quality. Therefore the strategy is easy to be realized in computer or distributed control system(DCS), so it has hopeful application prospect. Many computer simulation results show that the advanced control strategy has more favorable dynamic characteristics than PID cascade control strategy in main steam temperature system, disturbance rejection and robustness.

Zhou Li-hui

Papers

Studies and applications of pfc-pid cascade control stragety in main steam temperature control system