Xycom PM9450 计算机操作员界面屏幕监视器

跟踪支架的跟踪以水平位置为起点，启动控制系统的“东启模式”——在当地太阳升起后预设的时间段内采用相同时间间隔启动电机至设定的跟踪点；当东启的预设时间结束后，支架将从跟踪点开始进入“正常跟踪模式”——根据计算控制电机的运转使得跟踪太阳入射光线始终落于微倾角法向平面内；当到达日落前的预设时间段内，系统启动“夜返模式”——跟踪太阳落下前的遮挡回旋支架以获得的余光提高电站的日发电量。同时，整个控制系统中实时监测电站风速，当电站环境风速高于设定安全阈值时将调平支架，确保安全，当风速小于一定值时重新进入跟踪状态。

2.2 单控制器结构

整个控制系统结构仅由PLC控制器及现场设备层构成。

跟踪支架定位仪表——角位移传感器与控制器连接，控制器连接现场设备（比如现场的点击，各种传感器，智能仪表以及开关量等），起到对现场设备自动控制的作用。

2.3 控制系统硬件设计

2.3.1 控制单元

选择ABB公司AC500系列PLC的PM581-ETHCPU模块作为过程控制的中心控制单元。该CPU已含集成的装载存储器，用于保存用户程序和数据。

2.3.1 机械结构

单台试验样机采用单台电动推杆，通过钢丝绳柔性连接方式，同时对三台跟踪支架进行同步拖动，并设置其抗风等级为7级。

2.4 控制系统软件设计

系统的编程软件采用ABB公司的AutomationBuilderPS501V2.3版本。采用通俗易懂的梯形法及模块化编制控制程序，即将复杂的自动化任务分解成可以图形化程序语言，由相应的程序块来执行，程序运行时所需的大量数据和变量存储在数据块中，通过各程序模块之间的调用，实现系统的数据采集，过程控制和保护等复杂的控制算法。
similar to assembly language)and SFC(Sequential function chart).These techniques emphasize logical organization of operations.

While the fundamental concepts of PLC programming are common to all manufacturers,differences in I/O addressing,memory organization and instruction sets mean that PLC programs are never perfectly interchangeable between different makers.Even within the same product line of a single manufacturer,different models may not be directly compatible.

5.PLC compared with other control systems

PLCs are well-adapted to a range of automation tasks.These are typically industrial processes in manufacturing where the cost of developing and maintaining the automation system is high relative to the total cost of the automation,and where changes to the system would be expected during its operational life.PLCs contain bbbbb and output devices compatible with industrial pilot devices and controls;little electrical design is required,and the design problem centers on expressing the desired sequence of operations.PLC applications are typically highly customized systems so the cost of a packaged PLC is low compared to the cost of a specific custom-built controller design.On the other hand,in the case of mass-produced goods,customized control systems are economic due to the lower cost of the components,which can be optimally chosen instead of a"generic"solution,and where the non-recurring engineering charges are spread over thousands or millions of units.