Control System Optimization Of Typical Low Nitrogen Combustion AGC Unit Based On Model Technology

Low nitrogen combustion type AGC units are widely used in thermal power enterprises because they can effectively reduce NOx emissions and reduce air pollution. According to the latest revision of《Thermal Power Plant Emission Standard of Air Pollutants》(GB13223-2011), domestic requirements of active thermal power unit to complete low nitrogen transformation tasks, and the future of the new coal-fired units, requirements must be simultaneously supporting additional low nitrogen burners. This makes the future of China’s thermal power plant boiler using low nitrogen combustion technology to reduce NOx emissions is imperative. For the unit to participate in the operation of the AGC after the operation of low nitrogen combustion after the unit to the thermal power plant unit load tracking capability and its control system has brought new challenges. Combustion in the low NOx combustion generator sets in the process, this paper lag, large steam temperature fluctuation and the unit load tracking AGC capacity decline problem, the superheated steam temperature control and coordinated control system as the object of study unit control to improve the performance of research. The main content includes the following parts:1) Based on the field operation data by least square method for the model identification of superheated steam temperature control system and the coordinated control system of the controlled object, mathematical model has the typical characteristics of low nitrogen combustion of AGC units, at the same time, based on work principle of steam turbine considering steam temperature of a steam turbine load rate perturbations of the coordination control system model of the controlled object. The model group provides a model reference for the optimization of the control system of the superheated steam temperature and the design of the coordinated control system and the research of the decoupling algorithm.2) Based on the obtained controlled object math model from the identification, Low NOx combustion boiler side of superheated steam temperature control system were designed as cascade control system and in the original control parameters based on parameters optimization and tuning; for the coupling characteristics of the operation unit to output electric power and main steam pressure, and through a unilateral decoupling control strategy is designed for low nitrogen combustion unit coordinated control system of research and analysis, and in Matlab / Simulink construct control system model of the designed system is verified by simulation. The simulation results show that the superheated steam temperature control product quality has improved significantly, unit to output electric power control effect than the original system is improved.3) In view of the high temperature fluctuation of superheated steam and the increasing of delay time in the process of power generation with low nitrogen combustion unit. A predictive control algorithm with constrained optimization is proposed in this paper. The algorithm is applied to the main regulator of the superheated steam temperature control system in the power plant, which is a cascade predictive control system. The simulation results show that the system can operate safely and stably in the control range, and its anti-disturbance and robustness are superior to the conventional PID control system, and the quality of the superheated steam temperature control is greatly improved. Finally, based on predictive control algorithm considering steam turbine power under the influence of complex control system and simulation research. The simulation results show that using predictive control algorithm of the superheated steam temperature control system to smaller than the effect of conventional control system of unit power output variation. The conclusion to research on the economic operation of the unit of analysis has a certain reference value.