One. System overview
This system is the automatic control system of Guangchang pumping station in Zhuhai. Guangchang pumping station is a new pumping station to solve the problem of salt water supply in Zhuhai and Macao. Its daily supply of raw water can reach 800000 cubic meters. The automatic control system of the whole pumping station adopts centralized monitoring and decentralized control. The ControlLogix control system of AB company is used to integrate Ethernet, DeviceNet and MODBUS to form a perfect control system, which can complete the control and monitoring of the power distribution system of the whole pump station, the control and operation monitoring of the unit, the control and monitoring of the main outlet valve, the alarm of various switching and analog quantities, and the data acquisition.
Two. Application background and system selection
Since there are 17 integrated protectors in the whole pumping station (with RS232 / RS485 / optical fiber and data transmission through modbus, each integrated protector corresponds to a high-voltage switch cabinet) And 3 sets of 6kV high voltage inverter with DeviceNet interface from Toshiba company. According to our experience in using automation equipment, through careful analysis and comparison, we choose ControlLogix control system of AB company in the United States, with RSView 32 monitoring software, to realize the functions of the monitoring system of the pump station, and achieve the purpose of automatic control system.
1. Features of ControlLogix control system of AB company in USA:
·Seamless connection, easy to integrate with existing PLC system.
·The fast ControlLogix structure provides high-speed data transmission bus on the backplane, and the logix5550 controller provides the control platform for high-speed transmission.
·Configurable provides a modular control method.
·Industrialization improves the high-strength platform, which can withstand vibration, high temperature and various electrical interference.
·The integrated platform includes sequence control, motion control, transmission and process application control.
·Compact structure, suitable for highly decentralized control and distribution board space limited applications.
2. Monitoring Software RSView32
RSView32 is a software developed by Rockwell Automation Company, which can realize the human-machine interface of monitoring system by programming. The data collected by PLC is displayed vividly in various display forms through the configuration screen (as shown in Figure 1), and the information of the operator can be transmitted to PLC through the operation of the screen.
·It has powerful interface making function and communication function
·The operation is simple and clear
·The alarm mode is flexible and effective
·It has safe and stable operation performance
3、 System process and configuration
The system configuration is shown in the figure: (see Figure 1)
This system is an automatic control system based on ControlLogix architecture, which integrates Ethernet, DeviceNet and MODBUS network for centralized monitoring and decentralized control. The lowest layer of the system is the device control layer (DeviceNet Network and MODBUS network), which mainly completes the control and data acquisition of production equipment; The second layer is the network integration layer, which completes the network integration of the whole pumping station system. It is responsible for receiving the data transmitted by the lower layer and receiving the instructions from the upper layer, and transmitting the instructions to the equipment layer, and completing the data transmission and exchange between the monitoring layer and the equipment control layer; The third layer is the monitoring layer, which mainly completes the online monitoring and control of the whole pumping station automation control system, and transmits the information to the information management system of the head office and receives the information page］
1. Monitoring layer (control center)
The monitoring layer of the system is configured with RSView 32 software, which has the functions of control, data management, data acquisition, data recording, alarm, trend, report generation, etc. On the server, the engineer can manage, program and maintain the computer; In the operation station, the staff on duty can control the operation and monitor the production status（ (see Figure 2)
The main functions of the control center are as follows:
Control operation: in the control center, the controlled equipment on the system can be controlled online and in real time, such as the opening and closing of the switch cabinet, the opening and closing of the valve, the start and stop of the unit, the switching of linkage and single action, and the reset of PLC.
Display function: use graphics to reflect the running status of equipment and PLC in real time; Dynamic display of process flow chart and various parameters; Dynamic display analog value, switch signal, through the color, text display, percentage, fill and other means vividly expressed.
Data management: can establish production database, operation information database, fault information database
Data processing: use real-time data and historical data to analyze production cost and seek the best operation mode to achieve the purpose of energy saving
Alarm function: when the first mock exam (such as current, flow, pressure, temperature, etc.) exceeds the set range or a switch quantity (such as relay contact, contactor contact, valve position, etc.), it can be classified alarm according to different needs. Such as input to the alarm table, display in the screen alarm bar, sound and light alarm prompt, etc.
Report function: it can generate real-time report, daily report, monthly report and annual report.
Security function: encrypt according to different operation levels. Turn on the PC to automatically enter the monitoring system, the general operator can only operate within the permission of the runtime screen, and can not exit the runtime screen.
Printing function: it can print reports, graphics, events and alarms in real time.
2. Network integration layer
The network integration layer of the system integrates Ethernet, DeviceNet and MODBUS networks.
The hardware configuration is as follows:
·1756-pa72 power module
·1756-l1 logix5550 controller
·1756-dnb DeviceNet Network Communication Card
·1756-enet Ethernet network communication card
·Mvi56 MCM MODBUS network communication card
2.1 1756-l1 logix5550 controller
Logix5550 controller is the core of the system, which is programmed with software rslogix5000.
2.2 1756-dnb DeviceNet Network Communication Card
1756-dnb is the interface module of DeviceNet scanner, which acts as the interface between DeviceNet and ControlLogix rack.
1756-dnb communicates with DeviceNet network devices as follows:
·Read / write with device
·Download configuration data to device
·Monitor the working status of the equipment
The 1756-dnb communicates with the logix5550 controller in the ControlLogix rack to provide:
·Input / output (I / O) data of the device
·Status information of the device
·Read / write configuration data of equipment
2.3 1756-enet Ethernet network communication card
TCP / IP Ethernet is a local area network, which allows a large number of computers, controllers and other devices to communicate over Ethernet. The 1756-enet Ethernet communication interface module is used to bridge Ethernet with other networks. In this system, it is used to bridge Ethernet with dvicenet network and MODBUS network.
2.4 mvi56-mcm MODBUS network communication card
Mvi56-mcm is the gateway between MODBUS network and ControlLogix System Controller backplane. It provides 5000 word memory for data exchange between MODBUS network and controller.
2. Equipment control layer
3.1 dvicenet network (as shown in Figure 3)
Based on CANbus technology, DeviceNet is used for communication network between PLC and field devices. It can be connected with switch, driving device, power monitor, solid overload protection device, bar code reader, I / O and man-machine interface. The transmission rate is 125-500kbps and the transmission distance of coaxial cable is 500m. DeviceNet Network is an open network in line with international industry standards, which connects the underlying devices directly with the workshop level controller without connecting them with I / O module through hard wire. More than 150 vendors around the world actively support the can based network of ODVA.
This 64 node, multi branch network allows a single cable to connect the devices within 500m and as far as the user’s programmable controller, without wires to connect each device with an I / O rack. In a word, all these can reduce the cost of wires and facilitate installation.
3.1.1 4 # station ~ 8 # station correspond to 1 #~ 5 # butterfly valve control station, 9 #, 10 ＃, 14 ＃ and 15 ＃ stations correspond to fan control station, 12 ＃ and 13 ＃ stations correspond to standby station of high pressure chamber (the configuration of each station is the same)
The butterfly valve control station controls the opening / closing of butterfly valve and cooling water solenoid valve; Monitor the valve position of butterfly valve and the working condition of oil system, and count the pulse of cooling water flow.
The configuration is as follows:
3.1.2 1 ~ 3 stations correspond to three sets of inverter control stations
Inverter control station controls the start / stop and operation frequency of the inverter, and monitors the operation status, frequency, temperature, current and voltage of the inverter. The frequency converter is a Toshiba product, which is equipped with DeviceNet interface card.
3.1.3 main pipe valve control station corresponding to station 11
Main valve control station controls the opening / closing of main valve and monitors the working condition of valve.
The configuration is as follows:
3.1.4 analog acquisition station corresponding to 18 stations
Analog quantity collection station: monitoring flow, pressure, opening of main pipe valve, temperature and current of motor and water pump.
The configuration is as follows:
·1746-pa2 power supply
·1747-sdn device network scanner
·1746-slc-5 / 04 processor
·1746-nir4 analog module
·1746-ni8 analog module
3.2 MODBUS network
Modbus protocol is a general language used in electronic controller. Through this protocol, the controllers can communicate with each other and with other devices through the network. It has become a general industry standard. With it, the control equipment produced by different manufacturers can be connected into an industrial network for centralized monitoring. This protocol defines the message structure that a controller can recognize regardless of the network through which they communicate. It describes the process of a controller requesting access to other devices, if it responds
Requests from other devices, and how to detect errors and record them. It formulates the common format of message domain pattern and content. When communicating on a MODBUS network, this protocol determines that each controller needs to know their device address, identify the messages sent according to the address, and decide what kind of action to generate. If a response is required, the controller will generate a feedback message and send it using Modbus protocol.
The standard MODBUS port uses a RS-232C compatible serial interface, which defines the pin, cable, signal bit, baud rate and parity of the connection port. The controller can network directly or through modem. Controller communication uses master-slave technology, that is, only one device (master device) can initiate transmission (query). Other devices (slave devices) respond according to the number provided by the master device. The master device can communicate with the slave device alone or with all the slave devices in broadcast mode. If it communicates separately, the slave device will return a message as a response. If it queries by broadcast, it will not make any response. Modbus protocol establishes the main device query format: device (or broadcast) address, function code, all data to be sent, error detection domain. The slave response message is also composed of Modbus protocol, including the domain to confirm the action, any data to return, and error detection domain. If an error occurs during the message receiving process, or if the slave cannot execute its command, the slave will establish an error message and send it as a response. In this system, the 7sj62x series integrated protector of Siemens company is connected to the Modbus network communication card mvi56-mcm through RS485 interface. Through MODBUS network, it can realize the opening and closing control of each switch cabinet and monitor its status (opening and closing status, current value, voltage value, frequency, etc.).
4、 Concluding remarks
The system based on ControlLogix architecture has been running steadily and safely since it was put into operation in June 2001. The success of this system may have a certain reference for the automation of water supply industry.
Editor in charge: GT