| Steam turbine is widely used in electric power, metallurgy, steel, textiles, chemical industry, shipbuilding and other fields. In the power industry, in order to obtain higher thermal efficiency, lower manufacturing, installation and operation costs, steam turbines develop to the direction of high parameter, large capacity. This makes the unit more complex, more controlling factors in the process of variable conditions. For ensuring electric power system's safe operation and making power quality accorded with index, digital electro-hydraulic control system (DEH) has replaced original mechanical hydraulic control system. Now DEH system achieves speed control, load control and synchronization of steam turbine by different control regulation and different system configuration such as PID control, logic control and so on. So the control ability, control effect, adaptability and flexibility of the system have been changed fundamentally, and the automation level of turbo-generator unit has been improved greatly. DEH system has already become an important component of unit controls and even entire power plant controls. With the development of national economy and the changes in power consumption structure, DEH system faces the challenge of new problems in applications such as large load fluctuation conditions, isolated operation, etc. Therefore, it's very important to establish the simulation model of the turbine and study it.Based on the visual simulation support software VMS, this paper has increased graphic models and simulation modules which adapted to the DEH control system graphical modeling and enriched the VMS simulation modules library.Based on further study of principles, characteristics and operation mode of turbine control system, taking the GUIZHOU DALONG power plant 300MW turbine DEH control system as a research specimen, this paper uses simulation module library of VMS to configure and develop the 300 MW turbine DEH control system simulation model. The model includes DEH basic control system (set value generating system, speed control system and load control system.) and the main control functions except the valve test function.This paper makes parameter setting and simulation test study to DEH control system through DEH simulation model. Valve switching process, RUNBACK function and over speed protection function are studied mainly. One purpose is testing the reality and integrity of the system functions, the other is doing system research. Also it is a test of feasibility and performance to this simulation support software.In addition, for the special condition isolated operation, frequency control and the corresponding parameter setting is proposed. Simulation results show that the unit speed can be stable rapidly; the proposed control strategy is correct and reliable.This work has enriched and enhanced the functions of VMS, completely tested the availability, openness and maintainability of VMS. The control strategy and parameter settings proposed in this paper have certain reference value. This is very important to the extensive application of the DEH system. |
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