1、PDF外文：http:/ 翻译部分 2009 3rdInternational Conference on Power Electronics Systems and Applications PLC and Configuration Software Based Supervisory and Control System for Oil Tanks Area Xi CHEN1 YanboCHE1K.W.E CHENG2 1School of Electrical Engineering & Automation, Tia
2、njinUniversity, TianjinChina. E-mail: 2Department of Electrical Engineering, TheHong KongPolytechnicUniversity, Hong Kong, E-mail: eeechengpolyu.edu.HK Abstract - A supervisory and control system for oil tanks area based on PLC S7-300 and configuration software ForceControl is introduced in t
3、his paper. The hardware structure of the system and the software design are both described in detail. In this system, Superior computers communicate with PLC through Industrial Ethernet. The superior computers system adopts duplex redundancy and the PLC adopts software redundancy .This monitoring sy
4、stem integrates the merit of PLC and computer and improves the reliability. Keywords - PLC, configuration software, supervisory and control system, software redundancy I. I NTRODUCTION With the increasing competition of the oil marketoil depots are playing a more and more i
5、mportant role, and it has become a long-term important job to supervise and control the operation state of oil depots.This paper designs a supervisory and control system for a oil depot in ShandongProvince. This oil depot collected tank information and controlled valves manually before. There were s
6、ome shortcomings in it such as slow supervisory, great error and low reliability. So it is necessary to establish a better supervisory and control system that is timely, accurate and reliable. Programmable logic controllers PLC have been widely used in the industrial control fields because of its me
7、rits such as simple structure, flexible functions, high reliability and strong ability in communication. Computers have advantages in the data display and storage, as well as in human-computer communications. This paper designs a supervisory and control system for oil tanks area based on PLC and com
8、puter. PLC is the control centre and it completes all the details of the control task. It connects with digital and analog signals of field devices through general I/O interfaces, collects and process field data accurately and quickly, and completes thelogic,timing, counting and mathematicaloperatio
9、nseasily.Computers provide human-machine interface,display the feild working stastedynamicly, and makes the operation easy. The system combines the advantages of PLC and computer, provides a remote real-time monitoring for the tanks area, ensure safety and reliability and improves the work efficienc
10、y. Considering oil depots high requirements on reliability and continuity, redundancy scheme is designed to improve the reliability further. II. H ARDWARE O F T HE S YSTEM A. the Overall structure and functions 中国矿业大学 2012 届本科生毕业设计第 2 页 Fig. 1 Overall structure
11、 diagram of the system The structure of the supervisory system is shown in Fig. 1.There are three levels in the system : the first level is superior computers.They consist of dual redundant Industrial Computers installed with configuration software ForceControl and placed in the monitoring cen
12、ter room, the second level is S7-300 PLC that adopts software redundancy and is placed in the local control rooms,and the field devices including electrically operated valves and liquid level switches form the third level. Industrial Computers are connected to the Industrial Ethernet through general
13、 network cards and PLC is connected to the same net by Ethernet communication module , so they could accomplish the communication by using TCP/IP protocol. PLC collects feedback dates of electrically operated valves, collects the status of liquid level switches and opens or closes valves according t
14、o the command from superior computers and the control program in the CPU module. In addition, PLC completes the interlock control of valve and liquid level switch. By exchanging data with PLC, superior computers installed with ForceControl, monitor electrically operated valves and liquid level switc
15、hes in real time and give command to PLC to control the valves. Redundancy structure is adopted in the system. ForceControl has taken the lead in providing complete support for redundancy among the China-made configuration software products,and it supports device redundancy, network redundancy and s
16、uperior computer redundancy. There are two superior computers in the system, primary station and secondary station.In normal conditions, only the primary station communicates with PLC and the data in the secondary station synchronize with the primary station to make a backup. If the primary station
17、fails, the secondary takes over the job. And the job 2009 3rdInternational Conference on Power Electronics Systems and Applications Digital Reference: K210509077 could come back to the primary station or manually after the primary station returns normal. ForceControl supports PLC redundancy an
18、d normally communications with the master station of the PLC. If the master system of PLC is in the event of failure, the control job would be taken over by the reserve system, ForceControl would disconnect the communication according to the switch flag and turn to the reserve station to exchange da
19、tes. B. Hardware Design of PLC System Before selecting PLC modules, analyze the controlled object to count out I/O points.The current requirement and 20% -30% margin should be considered, allowing the system to expand. According to this principle, I/O points are as follows:125 digital inputs,2
20、1 analog inputs,84 digital outputs. Based on the analysis of control task, the system chooses Siemens S7-300 series of products. This series PLC could Meetrequirements of the medium-performance control system and adopt modular structure. Many different modules can be combined together and users shou
21、ld select appropriate modules according to the actual need. PLC modules selected are shown in Table 1. PLC in the system consists of two S7-300 stations each with a CPU 315-2DP and two ET200M slave stations.Its structure is shown in Figure 2. The Ethernet communication module CP343-1 provides
22、a standard RJ45 interface, one of the functions is to connect the PLC to Industrial Ethernet to communicate with computers, and the other function is to provide redundant backup link for master CPU and reserve CPU to realize redundant communication 中国矿业大学 2012 届本科生毕业设计第 3 页 between the
23、 two CPUs. Fig. 2 Hardware structure of PLC CPU315-2DP provides DP master interface and IM153-2 of ET200M provides two DP slave interfaces ,one is connected to the master station and the other to the reserve station through PROFIBUS-DP networks. PROFIBUS-DP could be S
24、hielded Twisted Pair(RS485) network physically. Normal ET200M consist of a rail, a interface module and some general modules .The modules except power supply are connected through bus connectors.This structure doesnt support redundantcy functions. There is another configuration that is suitable for
25、redundantcy. It uses a special rail that can take active bus modules and two interface modules. The modules except power supply are mounted on the active bus modules and it is possible to change modules during running. C. Connections of the Electrically Operated Valve Henchun CKD series electr
26、ic operators are used and Fig. 3 shows its connection method. The feedback of electrically operated valve includes four digital signals and one analog signal. Digital signals are remote mode indicating contact, full open indicating contact, full off indicating contact and common alarm contact. The a
27、nalog feedback, a 4-20mA current, shows the valves opening value .When the valve is in the remote control mode, digital outputs of PLC drive the relays and then control the valves. Four output control signals include open-valve signal, close-valve signal, stop signal and emergency protection signal
28、esd. Fig. 3 Valve connection diagram III. SOFTWARE OS THE SYSTEM Software in the system includes two major parts, PLC programming software STEP7 V5.4 and superior computer configuration software ForceControl V6.0. A. Communication between Superior Comput
29、er and PLC ForceControl develops a special driver for the S7-300 PLC, 2009 3rd International Conference on Power Electronics Systems and Applications Digital Reference: K210509077 therefore it is not necessary for the users to be familiar with the communication protocol between the
30、m, and neither necessary to program or configure network in the PLC, the communication between PC and PLC can be achieved easily. The main problem in this system is that due to PLC's soft redundant structure, when the control task switches to resereve CPU from the master one, ForceControl should
31、 switch to the correct communication object to exchange datas. For this purpose, when device PLC is created in ForceControl ,it should be configured properly and a data point should be defined in the real-time database as a redundancy switching flag. First configure I /O device for ForceContro
32、l, create PLC whose equipment address is set to 2, if set to 1, ForceControl will not be able to connect to the PLC. The standby channel is enabled and the device IP address and standby IP address should correspond with PLCs two Ethernet communication modules CP343-1. After I/O device PLC is created , define a data point in real-time database whose data type is selected as " redundancy switching flag ". The flags
