Dynamic Model And Simulation Of Gas-fired Cogeneration Units

Establishment of a simplified dynamic model and a general simulation platform for cogeneration units is a good method for the enterprise to optimize scheduling of power generation. The focus and challenges of this research is to build a thermodynamic model based on typical equipment of WISCO energy management demonstration project,and a simulation calculated on MATLAB platform by Simulink. The generator set is a very complex system, three major problems related to the system need to be investigated. The first one is to effectively simplify the system without affecting the accuracy of the model; the second one is how to simulate the system using the model by software; while the third one is to validate whether the model has the capacity to be effectively applied in practical production by error evaluation and finding out the reasons led to the error.This paper firstly described the operation characteristics of cogeneration unit with two 220 t/h boilers of Wuhan iron and steel corporation energy plant. Based on the mass and energy balance principle, gas combustion, boiler heat storage, superheater differential pressure, and dynamic characteristic of the turbine were analyzed. With respect to the units' parameters including pressure and output power, a simplified nonlinear dynamic model was established, which has capacity to simulate actual operational state in variable working conditions with wide range. The static parameters of the model were derived from monitoring data under stable running condition, while dynamic parameters are derived by turbine disturbance and fuel flow disturbance experiments.In addition, in this paper, the accuracy of the model was analyzed by simulation of the unit. The operation parameters under steady state operation conditions were used as the initial boundary conditions. Then the simulation predict the operation parameters with load change, including main steam pressure, inlet pressure of steam turbine, steam turbine output power and efficiency of the generating unit. The process of simulation was realized by Simulink based on MATLAB simulation platform.The simulation results showed that when the overall input energy was reduced more than 12%, the output power of the steam turbine reduced more than 13%, and the main steam pressure showed a rising trend. According to the simulation results, this paper analyzed the possible reasons for the operation parameters variation with change in load conditions. At the same time, the comparison between predicted results and monitoring data showed the relative error was less than 10%, which mean the model had great significance, could guide the unit scheduling, and achieved the goal of saving energy as well as reducing energy consumption.