Study On Online Performance Monitoring For The Transient Process Of A Coal-Fired Power Generating Unit

With the implement of reform on electric power industry in China, the power generation enterprises make efforts to reduce cost and improve efficiency of power generation. The Online Performance Monitoring System for Coal-fired Power Generating Unit has been applied more and more widely. Most of them do not consider the transient process of the unit. It is increasingly frequent for the large units to operate in load-changing mode because the more and more medium and small units are closed and the difference between peak load and valley load are becoming larger and larger. As a result, the transient processes of large-size coal-fired units are more and more important. Boiler is a main heat inertia equipment of coal-fired power generating unit in which there are many mass and heat storage processes. Study on online performance analysis considering transient processes of boiler and online calculation of transient characteristics for coal-fired power generating unit owns good academic and practical significance for perfection of online performance monitoring system and improvement of safety and efficiency.Study in the essay is carried out based on online performance monitoring for transient process of coal-fired power generating unit.Dynamic models for single-phase medium and two-phase medium are deeply studied. Detailed dynamic models for analysis are established. Hydrodynamic model for natural circulation system considering its dynamic characteristics is established for the first time.In order to improve the speed of online calculation of transient process, a new solution is put forward in which the simulation is divided into offline part and online part, precision and speed is achieved by a great deal of preparing calculation offline. Besides the separation of online and offline, there are two other sticking points. One is integrating variables in the model to cut down their number and classifying them, the other is the method in which initial value of unknown variable is altered is used to solve the problem which is caused by the variables varying with time in the differential equations.The new method is applied to single-phase dynamic model and two-phase dynamic model in boiler system. It is compared with the fourth Runge-Kutta method on precision and speed. The cause of error is analyzed. Speed and precision of the new method are proved by case studies.Modified dynamic model for equipment of boiler with different known conditions is established. The reason of difference between results calculated by steady model and dynamic model is analyzed. Thus the performance calculation model for transient process of coal-fired power generating unit is established for the first time. To analyze the direction in which the heat has gone in the transient process of boiler by heat distributing is brought forward for the first time, and the models for calculating the heat distributing of each equipment and whole boiler is established. Some views on efficiency evaluation of coal-fired power generating unit under unsteady conditions are discussed, and model calculating total coal consumption during a period of time is established. The integration, solution and realization of models are introduced. The integrated model is applied to the process of load-up and load-down, and the result is analyzed.The study is combined with The Online Performance Monitoring System for Coal-firedPower Generating Unit to apply to online performance monitoring and analysis, which is of great significance for improving safety and efficiency of power generating units.