Proceedings of 2013 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices Beijing, China, October 25-27, 2013
ID3072
LabVIEW-Based Multi-Channel Measurement and Protection System for HTS Device Applications Liang Wen, Xiao Yuan Chen, Lin Jiang, Jian Xun Jin Center of Applied Superconductivity and Electrical Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China
[email protected] Fig. 1 shows the block diagram of a typical temperature measurement system. The whole operation processes are as follows: 1) Select the COM communication channel to connect with the external digital thermometer; 2) Write the command of read the measurement data to the digital thermometer; 3) Set the data sampling rate; 4) Set the delayed time between the adjacent reading and writing operations, e.g., 60 ms; 5) Read the real-time data from the digital thermometer, and then convert the original string-type data into floating-point data; 6) Display the data in the front panel, and also save the data into the data files.
Abstract—This paper presents a VI based measurement and protection system for HTS device applications. The subsequent protection system has also been designed for the safe operation of HTS devices. The whole system has been tested and verified in superconducting magnetic energy storage (SMES) device. The results obtained prove that the VI measurement and protection system is easy to build and convenient to use with high precision control. Keywords-LabVIEW; HTS device; multi-channel measurement
I.
INTRODUCTION
In recent years, various high temperature superconducting (HTS) devices, e.g., HTS cable, HTS motor, HTS transformer, superconducting magnetic energy storage (SMES), have been developed and experimentally verified for use in modern power systems [1-7]. The HTS devices with the advantages of high efficiency and little pollution have the significant potentials to become available commercially and widely in near future. Since the physical characteristics of HTS conductors and relevant application characteristics in different HTS devices are fundamental, it is very important to measure those accurately in laboratory before practical application.
III.
A． Principle of Multi-Channel Measurement In the multi-parameters measurement applications, if every parameter to be measured has its independent meters, the multi-channel measurement system can be easily formed by multiple paralleled measurement units. Each unit has its independent COM channel, data processor, data displayer and data file. However, if the practical meters are not enough, LabVIEW can be applied to control the data selection module though a programmable communications interface (PCI). Fig. 2(a) and Fig. 2(b) show the flow diagram of the two multichannel measurement systems. In the Fig. 2(b), the number r of the available meters is less than the number n of the practical parameters.
Laboratory Virtual Instrument Engineering Workbench (LabVIEW) has become more and more popular in the measurement and test field, which has the flexibility of a programming language combined with built-in tools designed specifically for test, measurement, and control [8]. Thus the introduction of LabVIEW into the measurements of various HTS characteristics will make the experimental tests convenient and easy. Based on the using of commercial LabVIEW technology, this paper will present a multi-channel measurement and protection system designed for HTS device applications. II.
B． Case Design of a Eight-Channel System In this section, we will present an eight-channel temperature measurement system design. The temperature sensors used are eight copper-constantan thermocouples. The temperature meters used are two digital thermometers XSTH1ET2S1N. Three relays are used to form a data selection module, as shown in Fig. 3. With the assistance of PCI-6221, LabVIEW will output high-voltage level (“1”) or low-voltage level (“0”) to achieve the turn-on state or turn-off state of the relay. As shown in Fig. 4 and Table I, four kinds of voltage level, i.e., “000”, “011”, “100”, and “111”, will be applied to the three relays to achieve the eight-channel temperature measurement. The digital thermometer 1 is used to measure the real-time data of “data 1”, “data 2”, “data 3”, and “data 4”. The digital thermometer 2 is used to measure the real-time data
ONE-CHANNEL MEASUREMENT SYSTEM DESIGN
If only one operation parameter of the HTS devices needs to be measured by LabVIEW, a one-channel measurement system can be readily designed. Typically a sensor is used to acquire the real-time data and then transmit the data to its matched meter. Then the meter will send the data to LabVIEW with RS-232 or USB communication port.
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MULTI-CHANNEL MEASUREMENT SYSTEM DESIGN
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of “data 5”, “data 6”, “data 7”, and “data 8”. Assume that the maximum permissible sampling rate of the digital thermometer is N per second, thus the practical sampling rate of each realtime data is N / 4 per second.
modules are placed at the bottom of the figure. At the middle of is the sub-VI to get four voltage level shown in the Fig. 4. The other two are the same sub-VI is two-channel measurement system, it is formed by two paralleled the onechannel measurement system shown in the Fig. 1. The sampling data will be further sent to the data-saving module, which is placed at the top of the Fig. 5.
Fig. 5 shows a part of program code of the eight-channel temperature measurement system. Three paralleled sub-VI
Figure 1. The block diagram of a typical temperature measurement system.
TABLE I.
…
(a)
OUTPUT VOLTAGE LEVEL AND THE CORRESPONDING TEMPERATURE ACQUISITION CHANNELS
Output voltage level “000”
Digital thermometer 1 1
Digital thermometer 2 5
“011”
2
6
“100”
3
7
“111”
4
8
…
…
(b) Figure 2. Flow diagram of two multi-channel measurement systems: (a) n = r; (b) n < r.
Figure 5. A part of program code of the eight-channel temperature measurement system.
Fig. 6 shows the front panel of the eight-channel temperature measurement system. At the top of panel, there are eight temperature display windows. Under the eight temperature display windows, a running-time display window is applied to display the real-time data sampling rates of two digital thermometers. At the bottom of the panel, the COM channels and sampling rates can be pre-defined before the start of a practical measurement. The sampling data can be also selected to be saved in an Excel file or not. If some possible errors occur during the practical measurement process, the measurement operation will be interrupted after pressing the stop button.
Figure 3. Data selection module formed by three relays.
Figure 4. Program code to generate four digital voltage levels.
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Figure 6. Front panel of the eight-channel temperature measurement system.
IV.
operation states, i.e., charge state, storage state and discharge state. Two kinds of voltage levels, i.e., “0,0,1,0” and “0,1,0,0”, are corresponding to two transient operation states, i.e., transient storage state and transient discharge state. When the circuit is operated at storage state, it means that the circuit works in a safe condition. So when a fault occurs, the protection operation of the SMES device is to be converted from the current state to the storage state.
SUBSEQUENT PROTECTION SYSTEM DESIGN
For the protection system design, several threshold values are normally used to justify the operation faults of the HTS devices. Some typical cases are as follows: i) The operation current through HTS coil should be under its critical current value to avoid the occurrence of quench; ii) The operation temperature around the HTS coil should be above its critical temperature value to avoid the occurrence of quench; iii) The operation voltage across the HTS coil should be under its maximum isolation voltage to avoid the high-voltage breakdown. Fig. 7 shows a temperature protection system for a SMES device. TA is the temperature threshold value, TM is real-time measured temperature data. Assume the maximum allowable fluctuations of TA is 5 K, the whole protection processes are described as follows: i) When TM < TA - 5, the protection operation is not started; ii) When TA - 5 ≤ TM ≤ TA + 5, and the practical time duration lasts for 30 s or above, the protection operation will be started to protect the whole system; iii) When TM > TA + 5, the protection operation will be started immediately. The practical protection operation can be achieved by using the LabVIEW and PCI-6221 card. The digital output signals will be applied to the gate driver chips of the power switches used in the bridge-type chopper [9,10], as shown in Fig. 8. In practice, the system outputs high-voltage level (“1”) or lowvoltage level (“0”) to achieve the turn-on state or turn-off state of the power switches. Five operation states of the four power switches are used to control the superconducting coil in a SMES device. Three kinds of voltage level, i.e., “1,0,1,0”, “0,1,1,0”, and “0,1,0,1”, are corresponding to three steady
Figure 7. The overall flowchart of protection system design.
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shown in Table II. The system will output the signals of “Output1” firstly, and then output the signals of “Output2” after a time delay of 10 μs. The block diagram of the protection system is showed in Fig. 9.
L S1 DC Power
S4
S2
S3
C Load
TABLE II.
WORK STATE MAKE CORRESPONDING SWITCH ACTION TO PROTECT THE CIRCUIT
Figure 8. The circuit topology of a bridge-type chopper.
To avoid the short circuits of the power source and DC-link capacitor, the two transient operation states are necessary among the storage state and other two steady states, i.e., charge state and discharge state. In the practical protection system design, the turn-on state (“1”) or turn-off state (“0”) of power switches S1, S4 are firstly checked. Then the subsequent protections will be carried out according the different states, as
Check s1,s4
Output1 s1,s2,s3,s4
Output2 s1,s2,s3,s4
1,0
0,0,1,0
0,1,1,0
0,1
0,1,0,0
0,1,1,0
0,0
0,1,1,0
0,1,1,0
1,1
0,0,1,0
0,1,1,0
Figure 9. The block diagram of protection system.
V.
EXPERIMENTAL RESULTS
2
In the work, the designed measurement and protection system has been practical used for the data sampling and operation protection of a SMES device. The operation current IL(t) through the HTS coil, operation voltage UL(t) across the HTS coil, and the operation temperatures Tc1, Tc2 along the two current leads of the HTS coil have been obtained accurately for practical tests, as shown in Fig. 10, Fig. 11 and Fig. 12. The measured data is in very close to the practical values. What’s more, the protecion operation can be also started timely when a quench occurs. Fig. 13 shows the measured results of a slight quench when the practical operation current is somewhat above the critical current value. After about 5 s, the operation state is converted into storage state, and the current through the HTS coil decreases quickly to achieve an effective protection.
1.5 UL(t) [V]
1
0 -0.5 -1
0
10
20
30 t [s]
40
50
60
Figure 11. The measured results of UL(t).
130
70 60
120
50
110
Tc1, Tc2 [K]
I L(t) [A]
0.5
40 30
Tc1 Tc2
100 90
20
80
10 0
70 0
10
20
30 t [s]
40
50
60
0
10
20
30 t [s]
40
50
Figure 12. The measured results of Tc1, Tc2.
Figure 10. The measured results of IL(t).
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REFERENCES 70
[1]
J. X. Jin, L. H. Zheng, Y. G. Guo, J. G. Zhu, C. Grantham, C. C. Sorrell, and W. Xu, “High-temperature superconducting linear synchronous motors integrated with HTS magnetic levitation components,” IEEE Transactions on Applied Superconductivity, vol. 22, no. 5, pp. 5202617, 2012. [2] J. X. Jin, “High efficient DC power transmission using hightemperature superconductors,” Physica C, vol. 460-462, pp. 1443-1444, 2007. [3] J. X. Jin, and X. Y. Chen, “Study on the SMES application solutions for smart grid,” Physics Procedia, vol. 36, pp. 902-907, 2012. [4] X. Y. Chen, and J. X. Jin, “Analysis and modeling of the steady-state and dynamic-state discharge in SMES system,” Physics Procedia, vol. 36, pp. 995-1001, 2012. [5] X. Y. Chen, J. X. Jin, K. M. Ma, J. Wen, Y. Xin, and W. Z. Gong, “High temperature superconducting magnetic energy storage and its power control technology,” Journal of Electric Science and Technology of China, vol. 6, no. 2, pp. 137-142, 2008. [6] X. Y. Chen, and J. X. Jin, “Resonant circuit and magnetic field analysis of superconducting contactless power transfer,” 2011 International Conference on Applied Superconductivity and Electromagnetic Devices, pp. 5-8, Sydney, Australia, 14-16 December 2011. [7] X. Y. Chen, J. X. Jin, Y. G. Guo, and J. G. Zhu, “Design and analysis of a 10 kVA HTS transformer,” 11th International Conference on Electrical Machines and Systems, pp. 4302-4304, Wuhan, China, 17-20 October 2008. [8] Y. Chen, and J. X Jin, “Real-time measurement and control system for PMLSM based on virtual instrument,” 2011 IEEE International Conference on Applied Superconductivity and Electromagnetic Devices, pp. 243-247, Sydney, Australia, 14-16 December 2011. [9] Q. Zhou, Y. Gao, and Z. C. Fu, “Technique of data acquisition for linear induction motor based on LabVIEW,” 2012 International Symposium on Instrumentation and Measurement, Sensor Network and Automation, pp. 553-556, Sanya, China, 25-28 August 2012. [10] J. X. Jin, X. Y. Chen, X. Zhou, W. Xu, Y. C. Zhang, and Y. Xin, “Development of a new bridge-type chopper for low-voltage SMES applications,” 2013 IEEE Energy Conversion Congress and Exposition, pp. 5258-5265, Denver, USA, 15-17 September 2013.
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I L(t) [A]
50 40 30 20 10 0
0
5
10
15
20
25
30
35
t [s]
Figure 13. The measured results of IL(t) before and after quench protection.
VI.
CONCLUSION
The LabVIEW-based measurement and protection systems for HTS device practical applications have been presented. Two multi-channel measurement schemes have been designed when the number of the available meters equals to or is less than the number of the practical parameters. The subsequent protection system has also been introduced to achieve the safe operation of various HTS devices. The whole system has been tested for a superconducting magnetic energy storage (SMES) device. The results obtained prove that the VI measurement and protection system is effective, easy to build and convenient to use. As a universal measurement and protection system, the method and system developed in the work has a promising potential for various HTS device applications.
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