汽轮机最有利真空循环水泵变频驱动控制系统

A Variable-frequency Drive Control System of a Circulating Water Pump for Allowing a Steam Turbine Unit to Operate at an Optimum Vacuum

在火电厂中循环水流量大多采用节流调节方式 ,控制效果差 ,不能保证凝汽器工作在最有利真空值 ,而且循环水泵电耗严重。研制了一种循环水泵变频调速控制系统 ,利用PLC(可编程控制器 )设计合理的控制逻辑 ,实现平稳启停和切换 ,保证最有利真空值的实现 ,使汽轮机经济运行。同时分析了汽轮机的经济运行方式 ,给出了最有利真空值的计算原则 ;详细介绍了系统的控制原理、硬件结构及PLC程序的设计 。

Currently, thermal power plants adopt in most cases a throttle-governing mode for regulating the flow rate of circulating water. Such a regulating method suffers from poor control effectiveness and is incapable of ensuring that a steam condenser operates at a most favorable vacuum. Moreover, it also results in a high power consumption of circulating water pumps. In view of the above, the authors have developed a variable-frequency speed-governing system, using a programmable logic controller (PLC) to design a rational control logic. This makes it possible to realize a stable start-up, shutdown and the switching-over of the circulating water pumps, thus providing a steam turbine unit with an optimum vacuum for its economic operation. The economic operating modes of the steam turbine unit are analyzed and a method for calculating optimum vacuum values is given along with a detailed description of the system control theory, hardware configuration and PLC program design. Furthermore, some fruitful application results are presented.