Modeling And Simulation For A Steam Turbine And Its DEH System

Large-capacity thermal power plants have an important position in China’s thermalpower installed capacity and their off-design conditions time account for70percent of thelife. Researching the principal energy consumption in variable work conditions is of greatimportance for energy-saving and emission-reducing. Thermal energy is converted intomechanical energy by the steam turbine, which is a rotating machinery belong to the threemain components in large thermal power plants. The principal energy consumption and thecharacteristic of the steam turbine are studied by establishing a simulation modelconsidering the interaction between the subsystems and operational parameters. It is a novelmethod providing the foundation on solving energy-saving and emission reductionproblems of coal-fired generators.The paper is based on the background of the research on energy saving optimizationoperation of steam turbine. It takes a600MW supercritical steam turbine as research object,analyzing the characteristic of steam turbine, after the steam turbine mathematical model isprovided using the tool of Matlab/Simulink, along with a hierarchical modeling complexsystem approach. Some components’ thermal models, including high-pressure main valves,high-pressure governor valves, intermediate-pressure main valves, intermediate-pressuregovernor valves, control stage, pressure stages, reheated steam valves, pipes connectingintermediate-pressure cylinder to the low-pressure cylinder and exhaust pipes, areestablished based on the mass-balance and energy-balance equations. Simulation resultsunder designed data in the different design conditions, operating data in different operatingconditions are compared. The results of the extraction parameters in two conditions showsthat the error is quite small and the results meet the requirement of precision. Thus thesteam turbine model can simulate the thermal parameters under different load conditions.Considering the current situation of the application of digital electric hydraulic (DEH)Control System in power plant, the paper briefly introduced the structure of hydraulicpressure servo system. Under the platform of Simulink, equipments and the overallhydraulic pressure servo system models were established along with the physical objectoriented modeling approach. Some components’ models, including EH oil pump system、 electro-hydraulic servovalve、oil servo motor were simulated in different conditions. Then,this paper combined with simulation models of the steam turbine and digital electrichydraulic (DEH) Control System, the connecting models exhibits rotary speed control andload control functions.The work of this paper has provided a foundation for the research on the off-designcharacteristics of steam turbine And the model of steam turbine could be better used toenergy saving and optimization operation of steam turbine.