Mathematical model for ultra-supercritical unit by physical principles

Large supercritical units are the future development direction of large-scale thermal power plants. Dynamic modeling of power plants is fundamental to control system design and performance studies. This paper aims to study the whole process mathematical model of 1000 MW ultra-supercritical unit. Based on mechanism analysis and model simplification, boiler is divided into four parts including the economizer, the water wall, the moisture separator and the super-heater. During the process of modeling, the positions of phase transition points are taken as independent variables. It successfully resolves problems exist in the unit during dynamic simulation under supercritical conditions. The derivative terms in the right of secondary modeling equations are eliminated by proper mathematical processing, therefore, the stability of numerical integration is improved. Furthermore, turbine model is established by using Friuli Greig formula. The dynamic characteristics of the unit are analyzed after simulation at 100% and 50% load conditions. The results generally agreed with the actual operating experience.