火电厂再热蒸汽温度控制系统的设计

摘要

锅炉蒸汽温度自动控制包括过热蒸汽温度控制和再热蒸汽温度控制。再热蒸汽温度是锅炉运行质量的重要指标之一，再热蒸汽温度过高或过低都会显著地影响电厂的安全性和经济性。再热循环可以降低汽轮机尾部叶片处的蒸汽湿度，降低汽耗，提高电厂的热循环效率，所以单元机组普遍采用中间再热技术[1-2]。本次毕业设计以再热蒸汽温度为被控对象，设计相应的控制器使再热器出口蒸汽温度在允许范围内，并且保护再热器，使管壁温度不超过允许的工作温度。

火电厂对再热蒸汽汽温控制若采用常规串级控制系统，具有很大的迟延性，对此，本文采用模糊控制和PID相结合的控制方式。实验结果显示，系统的控制特性在超调量、快速性、抗干扰方面都有了很大的改善，对大范围工况变化具有较强的鲁棒性和适应性，对大型发电机组的锅炉再热蒸汽汽温控制具有实用价值。

关键词：再热蒸汽；模糊控制；串级控制系统

Abstract

Boiler steam temperature control includes control of superheated steam temperature and reheat steam temperature control. Reheat steam temperature is one of the important indicators of the quality of boiler operation, reheat steam temperature which is too high or too low will significantly affect plant safety and economy. Reheat cycle can reduce steam turbine moisture at the end of the leaves, reduce gas consumption and increase power plant thermal cycle efficiency, so reheat units commonly is used in the unit. The graduation project make the reheat steam temperature as controlled object, the corresponding controller is designed to reheat outlet steam temperature in the allowed range, to protect the reheater, the wall temperature does not exceed the allowable operating temperature.

If steam temperature control uses a conventional cascade control system ,it has a great delay.therefore,this paper combines fuzzy control with PID control to improve . Experimental results show that the control characteristics of the system in the overshoot, fast and interference aspects have substantial improvement , it has significantly robustness and adaptivity when conditions change on a wide range , it has a practical value for large-scale generating units reheat steam boiler Steam temperature control.

Keywords: reheat steam; fuzzy control; cascade control system

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