Available online at www.sciencedirect.com Procedia Engineering 15 (2011) 938 943 Advanced in Control Engineeringand Information Science Integrated Monitoring System Design of Hybrid Airs Huibin Liang a*,xuehua Li b a College of Mechanical and Electronic Engineering, Shandong University of Science and Technology, Qingdao, Shandong Province 266510, China b Engineering Training Center, Shandong University of Science and Technology, Qingdao, Shandong Province 266510, China Abstract A hybrid air-s integrated monitoring system has been developed basing on the retrofit of air- control system in a certain mine of Shandong province. The air pressure principle and the same operation load rate principle are adopted in this system and the communication network is set up through the use of Industrial Ethernet and Profibus-DP Industrial bus. And the local, remote and network monitoring of one drive two control of screw air group by high-voltage soft starter and one drive three piston air-s by inverter and cooling water circulation system are achieved through PC and PLC. In this system, the automatic control of air operation is realized according to the amount of input air, and thus the flexible air supply is achieved. The mechanical abrasion of the air has been reduced and coal mine production safety has been ensured. It is suitable for the system to use the distributed control of hybrid air processor group, which is of great value in the energy-saving upgrade of the air group control system. 2011 Published by Elsevier Ltd. Open access under CC BY-NC-ND license. Selection and/or peer-review under responsibility of [CEIS 2011] Key words:air Compressor Unit; Inverter; High-Voltage Soft Starter; PLC; Profibus-DP 1. Introduction Air is the necessary equipment for the mine production and bears the power-supply of pneumatic machinery and main well unloading machinery of the mine. It runs day and night costs about 10% of the total power-consumption of the mine. The reliability and safety of its operation can directly affect the production safety and economical benefits. There are five air-s in mine air- 1877-7058 2011 Published by Elsevier Ltd. doi:10.1016/j.proeng.2011.08.173 Open access under CC BY-NC-ND license.
Huibin Liang and Xuehua Li / Procedia Engineering 15 (2011) 938 943 939 room, among which two are screw air-s and the other three are piston airs. The two screw air-s are just controlled by the controller of it and the measured parameters are few. Remote control of them cannot be achieved. The power-supply is aging and direct full-voltage is adopted in the start of the machine and great impact is made on the grid and equipment by the start current. Three piston air-s was reduced voltage stated by use autotransformer with high current, less self-protection function, high failure rate, magnitude of maintenance, the ratio 10:14 of load and unload run-time, and large energy-consumption. Every set of five air-s is controlled to be Started and stopped by manual ways, whose cooling system adopts water-cooled ways. In connection with the shortcomings of air- control system discussed above, a hybrid model air-s automatic monitoring system has been developed making energy-saving and information integration as the goal. The automatic control and flexible air supply of the main system and auxiliary cooling system of the air-s have been achieved and the energy has been saved at the same time. The automation and reliability of the air-supply system have been improved and the production safety has been ensured in coal mines. 2. Structures and Features of System Control 2.1. Design of the system A new control system suitable for hybrid air-s has been put forward in this article. In this system, the screw air-s were taken as the main air-supply whiles the piston air-s as the auxiliary air-supply according to the better stability of screw air-s. The air pressure principle and the same operation load rate principle have been adopted in this system and the communication network has been set up through the use of Industrial Ethernet and ProfiBus-DP Industrial bus. And the local, remote and network monitoring of one drive two screw air s by highvoltage soft starter and one drive three piston air-s by inverter and cooling water circulation system are achieved through PC and PLC. Finally, the flexible air supply has been achieved in the airs system. The communication network has a wide range of data communication capacities and features of openness and compatibility. The multi-party communications are achieved between the different models of Siemens controllers and other types of controllers and the follow-up devices can also continue to be configured on this network. Thus the upgrade of the system expansion is solved and the information sharing online is achieved by the link between Ethernet and the upper enterprise information system. A new distributed control and information management mode are formed through this open communication network design. The PLC technology, ProfiBus-DP industrial bus technology, Industrial Ethernet communication technology, automatic control technology, high-voltage soft start and low-voltage frequency conversion technology, etc have been fully integrated and applied in this system and the automatic monitoring of hybrid air-s and the equipment digital management have been achieved. 2.2. Structure of system control (Figure 1)
940 Huibin Liang and Xuehua Li / Procedia Engineering 15 (2011) 938 943 PC Ethernet Centralized Control Platform Touch Screen High-voltage soft start cabinet Frequency conversion cabinet Piston s local control cabinet Cooling-water control cabinet Screw s local control cabinet 1#2# high voltage motor 3#4#5# motor Piston s group Cooling pump units Screw s group Fig.1. the Hybrid s distributed monitoring system 3. Hardware Design of the System 3.1. Hardware structure and control of the system The hardware of the system consists of the followings: five air-s, six water pumps, one PC, one supervisory control cabinet (containing touch screen), one cooling-water control cabinet, one set of SMC soft start equipment(containing one driver two high-voltage power switch cabinet ), one set of Siemens Micro Master 440 converter equipment(containing one driver three low-voltage power switch cabinet), three sets of Siemens S7 series PLC(CPU315-2DP CPU224&CPU226CN) and related sensors. The system hardware structure has been shown in figure2. PC Touch screen Alarm Display Print Local PLC (Ethernet & DP bus) Current voltage transmitter Temperature transmitter Pressure transmitter Switching value state sensors No.1 screw No.2 screw No.3 piston No.4 piston No.5 piston Cooling-water pumps A set of high-voltage soft starter drives two motors switching cabinet A set of low-voltage frequency inverter drives three motors switching cabinet Fig.2. the Hardware structure of the system When the system is in operation, the outlet air pressure threshold is set through the touch screen of centralized control platform and one screw air- is first started by high-voltage soft start of PLC control system (The mutual spare principle is adopted for the two screw air-s). If windsupply air pressure cannot meet that of consumption of compressed air, the three piston air-s will supplement the compressed air driven by converter. According to the changes of compressed air pressure and the state of inverter, PLC control system can adjust the running number of piston airs. During the operation, if there is something wrong with the screw air-s, the piston air-s will run automatically through the system. If a piston air- is out of work, or one screw air- and three piston air-s are all in operation and cannot meet the airsupply, the other spare screw air- will be started through high-voltage soft start by system.
Huibin Liang and Xuehua Li / Procedia Engineering 15 (2011) 938 943 941 3.2. Control design of screw air- group Control methods of screw air- group The screw air-s are drove by high-voltage soft-starter to reduce the impact of the starting current on grid, alleviate the mechanical impact on the equipment and improve the reliability of the equipment in operation [1]. The way of one drive two is adopted to save the cost because of the different starting time of the two screw air-s. As for the two screw air-s, one is used as the machine in operation and the other as the spare one. To start the spare machine and stop the one can be automatic control in period. And thus, the regular check of the equipment is becoming easy. This method can not only improve the starting ability and reduce the mechanical loss but also improve the reliability of the equipment. Hardware design of screw air- group The system is equipped with the solid soft-start cabinet and soft start power switching cabinet with the function of protecting the high-voltage motor and the function of high-voltage one driver two soft start of the screw air s and emergent frequency direct start is achieved; the air inlet differential pressure, air-cooler and outlet pressure sensor are installed and the dynamic testing air filters, oil separator filters and the timely warning filters blockage are achieved through the control system. The high-voltage soft start control system mainly consists of S7-200DP sub-station, a Rockwell SMC soft starter, two sets of motor integrated protector, three sets of vacuum circuit breakers and five sets of vacuum contactors. 3.3. Control design of piston air- group Control method of piston air- group The piston air- control system replaces the existing relay-control system which consists of S7-300PLC and S7-200DP sub-station. The inverter is chosen to drive the three piston air-s alternately according to the feature of the minor change of air-consumption in a short time. The general pressure monitoring value and setting value are transferred to inverter through industrial bus and CB communication board by S7-300 PLC. The speed of motor is controlled by the internal PID regulating function to make the actual pressure value close to the set value constantly. When the air-load needs one piston air- s operation, the single air is in inverter-operation to maintain the constant pressure air-supply; when the load increases, the original inverter-operation automatically turns into the powerfrequency-operation. And the next piston air- will be driven in inverteroperation to maintain the constant pressure air-supply [2]. The automatic adjustment of the frequency, switching of the piston air- between powerfrequency and the inverter, the running number of the piston air-s are achieved in this system. Hardware design of the piston air- group The inverter and power switching cabinet are installed in the power circuit of air- group and one inverter drive three piston air-s to realize the dynamic adjustment of airflow; the pressure-sensors are installed to check the first-release pressure, the second-release pressure, gasholder pressure, after-filtered lubrication oil pressure and feed-water pressure of cooling-water; temperature sensors are installed to check the first-release temperature, the second-release temperature, gasholder temperature, lubrication oil temperature and temperature signal of cooling water[3]. The Siemens MM440 torque inverter with an efficient starting torque is selected. 3.4. Design of cooling-water control system
942 Huibin Liang and Xuehua Li / Procedia Engineering 15 (2011) 938 943 The hydraulic pressure stable principle is adopted in the cooling water control system and the automatic switching and the circulating start and stop of the pumps are realized through checking the main pressure change of cooling water. The coordinated control between cooling-water control system and air-s control system is realized. That is, the water inlet and outlet of electric valve should be turned on first before the start of a certain air- and the numbers of running pumps can be realized automatically according to the hydraulic pressure. During the operation of the air-s, if the electric valve is out of work or cooling-water temperature or pressure fault is checked, the corresponding air- will stop automatically and send error signals [4]. The Siemens S7-200PLC is the core of cooling-water control system and the corresponding electric valves, electromagnetic valves, liquid level detection sensor are installed. According to the change of main outlet pressure value and start-stop threshold, PLC achieves the control of the pump start-stop and the on-off of cooling circuit of the related air-s through DP bus and the substation. Not only are the safety operation and remote monitoring of the pumps achieved but also the energy can be saved by adopting this system. 3.5. Configuration of system monitoring The PC net monitoring can be realized through the connection between the Industrial Ethernet and Siemens S7. The remote configuration of the IM153 slave and the inverter, high-voltage soft starter, S7-200PLC and Mitsubishi PLC are realized by S7-300PLC (315-2DP CPU) which is the master of the ProFibus-DP bus and the dynamic monitoring, alarm, record analysis and report-forming and curvereporting are finished. S7-300PLC is responsible for the checking and handling the data of pressure and temperature sent by sensors and uploads the operation state of the air- group to PC through Ethernet. The local, remote, and net monitoring of the air- s main system and auxiliary system are realized through each system s control of Ethernet after the data from master being handled by PC through WinCC monitoring program. The centralized monitoring, operation, management and distributed control of the operation process of the air- group are carried out through industrial bus and computer technology and the remote control and the unattended of the air- group are realized. 4. Software Design of the System 4.1. Composition and procedure of the software The coordination management of the five air-s in the air- room is finished through the system software. The management includes the followings: the automatic control program and signal collection and processing program of the screw air- and piston air- are programmed by Siemens Step7; the configuration program of the touch screen is performed by WinCCFlexible; configuration monitoring program of PC is performed by WinCC; by human-machine interface on touch screen the set of the parameters of the system, the choice of the various control modes, the real time dynamic display of the system operation parameters and the error information are displayed through PC configuration monitoring program by control center at the scene. The PLC main program has a complicate function and the structuralized programming method is adopted in the program. The whole program can be divided into six subprogram modes: initialization, analog acquisition, communication, stop/alarm, the manual and the automation. And the subprogram modes are organized and executed in the main program mode OB1. The program development period is shortened adopting this method and the structure of the program is clear; some programs are generalized and standardized and easy to be modified and debugged.
Huibin Liang and Xuehua Li / Procedia Engineering 15 (2011) 938 943 943 4.2. Configuration design of touch screen. The Siemens WinCCFlexible configuration software is used in the touch screen configuration software and the interface layout of the whole monitoring system can be divided into the static region and dynamic region. The static region is fixed during the process of picture-switching and lies in the top of the interface. And the seven switching buttons are set: screen-monitoring button, parameter-setting button, switching-state button, error-centre button, alarm-inquiry button, operation-state button and system management button. The dynamic parts under the static part are the corresponding screens of the seven switching buttons and with the pressing of the different switching buttons; the different screen can appear. 5. Conclusions The continuous dynamic adjustment of air-supply of air- has been realized and the closelooped control of constant air-pressure has been realized through the intelligent monitoring system of hybrid air-s. The system has been put into operation in a mine of Shandong province and runs well. The full approval has been got by the customers; good social and economic benefits are gained as well. It is suitable for the distributed control of hybrid air- group and of great value in the energy-saving upgrade of the air group control system. Acknowledgements The financial support of SDUST Research Fund (2010KYTD101) is gratefully acknowledged. References [1]Jun Bao, Heping Zhang. Energy Saving Method of Air Compressor Wit Monitor. General Machinery, 2007(1)1, p. 60-62. [2]Zhihua Xu. Screw Compressor Energy Saving Transformation of Frequency Conversion.Energy and Environment 2009(6), p. 29-31. [3]Zhongyu Tang, Hongmei Liao. Air Compressor Sets Energy-saving Constant Pressure Gas Supply Control System. Coal Science and Technology, 2003(5), p.26. [4]Jianbin Xu. Design of Coal Screw Air Compressor Control System. SCI-TECH Information Development and Economy,2009(2), p.194-196.