One of the major bottlenecks of the traditional current transformer energy harvester (CTEH) is the instable output induced by the wide-range variations of the current in transmission lines. In this work, a novel CTEH capable of generating a stable output is demonstrated by using a core fabricated with saturable magnetic material. The stable output of the CTEH is enabled by the constant voltage-time product in its saturable characteristic. The proposed CTEH is implemented with a resistive load representing the load of electronic devices. When the current in the primary side of the CTEH's increases from 1 to 1000 A, the maximum power on the load can reach about 0.5 W, demonstrating the feasibility of using the CTEH with the saturable magnetic core as a quasi-stable power supply

Cao, JA

Jiao, YL

Li, YJ

Meng, GF

Peng, J

Pirri, F

Stassi, S

English

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

29 March 2023POLITECNICO DI TORINORepository ISTITUZIONALEA current transformer energy harvester with stable output based on the saturable magnetic core / Cao, Ja; Jiao, Yl;Meng, Gf; Peng, J; Stassi, S; Pirri, F; Li, Yj. - In: ELECTRONICS LETTERS. - ISSN 0013-5194. - ELETTRONICO. -58:18(2022), pp. 705-707. [10.1049/ell2.12566]OriginalA current transformer energy harvester with stable output based on the saturable magnetic corePublisher:PublishedDOI:10.1049/ell2.12566Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2974498 since: 2023-01-11T09:51:22ZWILEYA current transformer energy harvester with stableoutput based on the saturable magnetic coreJianan Cao,1,✉ Yuanliang Jiao,1 Gefei Meng,1 Jia Peng,1Stefano Stassi,2 Fabrizio Pirri,2 and Yunjia Li11Xi’an Jiaotong University, Xi’an City, China2Politecnico di Torino, Corso Duca degli Abruzzi, Torino, Italy✉Email: Caoja@mail.xjtu.edu.cnOne of the major bottlenecks of the traditional current transformer en-ergy harvester (CTEH) is the instable output induced by the wide-rangevariations of the current in transmission lines. In this work, a novelCTEH capable of generating a stable output is demonstrated by usinga core fabricated with saturable magnetic material. The stable outputof the CTEH is enabled by the constant voltage-time product in its sat-urable characteristic. The proposed CTEH is implemented with a re-sistive load representing the load of electronic devices. When the cur-rent in the primary side of the CTEH’s increases from 1 to 1000 A,the maximum power on the load can reach about 0.5 W, demonstratingthe feasibility of using the CTEH with the saturable magnetic core as aquasi-stable power supply.Introduction: The rapid increase in the number of industrial wirelesssensor nodes demands new power supply options. For the in-situ moni-toring of high-voltage transmission lines, common power supplies, suchas solar energy [1], wind energy, battery or laser energy [2], are knownto have insufficient stability and sustainability. In comparison, it is morereasonable to generate power from the current transmitted in the high-voltage transmission lines, namely the current transformer (CT) princi-ple. However, the output power of CT is often either too low or saturated,as a result of the wide range of transmitted current between a few am-peres to thousands of amperes. The low output power may not be enoughto supply energy to the electronic devices, while the surplus power mustbe consumed in order to avoid the damage of electronics devices. Es-pecially, when the short-term surge current presents in the transmissionlines, the CT’s magnetic core might be saturated, overheated and evenburned. One way to desaturate the magnetic core under high current isto use a bleeder circuit on the CT’s secondary side [3], for example, a sta-ble power output of 0.65 W is realized when the CT primary side currentis in the range of 17 to 500 A. Furthermore, CT with multiple secondaryside taps and short-circuiting taps implemented with electronic switchesis shown to be effective in avoiding the saturation of CT magnetic core ina wide current range and supply sufficient energy [4]. Similarly, a desat-uration controller [5] might be used to harvest energy from power line,where energy harvesting efficiency is improved by 13.7%. In addition, atraditional CT might be implemented with an air gap cutting structure inthe CT magnetic core [6], enabling 10-W output power with transmittedcurrent between 100 and 1000 A. As an alternative approach, a capaci-tance compensation circuit can be utilized to desaturate the CT magneticcore and harvest energy effectively [7]. The CT energy harvester, afteroptimizing the parameters, can increase the output power and work in awide range of current in the transmission line. In fact, for a CT with pre-defined physical parameters, its maximum harvesting power is directlyproportional to the square of the primary current [8]. Therefore, withthe increase in the transmitted current, the energy harvested by the CT’ssecondary side will increase correspondingly.Despite the excellent energy-harvesting capability in the unsaturatedstate, most of the CT energy harvesters can yet not harvest energy effec-tively when its core is saturated. In addition, it is not possible to avoidthe damage caused by the surge of large current in the transmission line.Consequently, these harvesters may suffer from serious heating problemsunder the high current condition for a long time.In this work, a CT energy harvester (CTEH)-based saturable magneticcore is proposed, capable of generate stable output power in the largecurrent range of the transmission line. The main novelty of this workis the CT’s easiness of saturation and high capability of power genera-tion enabled by the extremely high relative permeability of the magneticFig. 1 CTEH circuit. CTEH, current transformer energy harvester.core material. Meanwhile, the narrow magnetic hysteresis of the materialmade it possible to generate the much low loss. The working principle,design, and first characterization results of the CTEH are presented inthis paper.Operating principle of CTEH: The saturable magnetic material refers tothe materials with very high relative permeability (up to 106) and smallcoercive, giving rise to a quasi-rectangular shaped hysteresis loop. Thecommon saturable magnetic materials mainly include the Cobalt-basedmaterial, Permalloy and Supermendur. A CTEH processed with thosemagnetic materials is shown in Figure 1.Generally, the primary side of CT is the transmission line, equivalentto one turn, and its secondary side is designed to N turns, wound aroundthose ring-shaped magnetic materials. When the primary side currentip(t) is transmitted, according to Ampere’s circuital theorem, the sec-ondary side current is(t) is generated and its induced voltage is denotedas vs(t). Then after rectified bridge and filter C, the output voltage Uo isobtained to supply energy to load RL. During this period, the hysteresisprocessing of the saturable core is shown in Figure 2.In the magnetization curve, the point b is the saturated magnetic fluxdensity denoted as Bs, and the corresponding field intensity is Hs. Theremanence is denoted as Br (shown in point a in the figure), and the co-ercive force is denoted as Hr. Taking the quasi-rectangular shaped hys-teresis loop of Cobalt-based as an example, the saturated magnetic fluxdensity of point c is almost equal to that of point b, which is about 0.55Tesla, and the rate of Br and Bs is above 0.85.When ip(t) increases from zero to the value of it1, the magnetizationchanges from the point a’ to the point b on the curve. In this process, theflux density B is changed from −Br to Bs, so the induction voltage vs(t) isgenerated in the secondary winding of the CTEH. When ip(t) continuesto increase to the value of ip-pk, the magnetization curve increases frompoints b to c. In this process, the magnetic core remains saturated, andthe variation of magnetic flux density from points b to c is zero. Asa result, vs(t) is decreased to zero. Furthermore, when ip(t) decreasesfrom ip-pk to zero, the magnetization curve moves from points c to a. Thevariation of magnetic flux density at these two points is equal to (Bs–Br),less than 0.15, and then vs(t) should be small, approximately zero. Asthe negative half cycle of the magnetization begins, the magnetic core isreleased from the saturation state and a negative voltage is induced. Theshaded area in Figure 2 represents the period of time when vs(t) can begenerated in the secondary winding of the CTEH.According to Ampere’s circuital theorem, the magnetic field intensityH is H = k × ip, where k is determined by the ratio of the number of thewinding turns to the length of the effective magnetic path. When H isnoted as Hs, ip is defined as the saturated current it1. When the magneticcore of CT is determined, Hs is the fixed value and so is it1. As shownin Figure 2, the variation of current it1 is trivial regardless the change ofvalue of ip(t). Therefore, the saturated time t1 can be obtained.ip(t) is expressed as ip(t) = ip-pk ×sin(2π f × t), and f is the line fre-quency. When the current value is it1, the corresponding time t1 can beexpressed as follows:t1 = 1ωarcsin(it1ip−pk)(1)ELECTRONICS LETTERS August 2022 Vol. 58 No. 18 wileyonlinelibrary.com/iet-el 705 1350911x, 2022, 18, Downloaded from https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/ell2.12566 by CochraneItalia, Wiley Online Library on [11/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons LicenseFig. 2 Operating principle of CTEHIt can be concluded from Equation (1) that t1 decreases with the in-crease of ip(t). And with the decrease in ip(t), the saturated time increasesto t2 shown as Figure 2.The secondary side induces voltage vs(t) of CTEH as follows:vs(t ) = −N × B × S/t (2)For the CTEH with the saturable magnetic core, the value t is thetime when vs(t) is generated before the magnetic core is saturated andequal to t1 or t2 in Figure 2. B equal to 2Bs is a fixed value, that is, 1.1Tesla for the Cobalt-based material. N, the CT’s secondary side turns Ns,and S, the CT’s magnetic core sectional area, are both defined value.The voltage second product  is defined as:  = vs(t) × t. That is = vs (t ) × t = −N × 2Bs × S (3)Therefore,  can be fixed. Furthermore, if T is the period for thetransmission line current, the output average voltage Uo in Figure 1 isequal to 2/T. That means, the CTEH can supply stable output voltageUo for electronic devices, independent of the variation of the CT primaryside current ip(t). That isUo = −4N × Bs × S/T (4)Materials and methods: According to the scheme illustrated in Figure 1,the prototype for the experiment and verification is built as shown inFigure 3. The CTEH is a ring-shaped saturable core winded with coils,Fig. 3 CTEH prototype for experiment and verificationFig. 4 Voltage and current waveforms of CT primary side and secondarysideand it is installed around the transmission line. The CTEH magneticcore is fabricated with a Cobalt-based material 6025 Z from VAC Com-pany, with the model number E4030W543. The transmission line currentranged from 1 to 1000 A and is generated by the current source of modelSDDL-3000A. Observing and recording waveforms are achieved by theoscilloscope of model LeCroy’s HDO4054. The voltage second productof the magnetic core is a constant and will be integrated by the oscillo-scope.The CTEH primary side has one turn while the secondary side has 90turns. RL is 220  and C is 220 μF.The voltage and current waveforms of the CTEH primary and the sec-ondary are shown in Figure 4. The ratio of ip(t) is 1V/500 A according toRogowski probe calibration, and the ratio of is(t) is 1 V/1 A measured byconnecting 1 Ohm resistance in series. When the transmission line cur-rent ip(t) is about 25 A excited by the current source, the CT’s secondaryside peak voltage vs(t) is about 5 V, while the current is(t) is rectified andfed through a constant load RL connected to the capacitor C in Figure 1.The capacitor C can smooth and filter the output voltage Uo, then outputpower is Uo2/RL.Results and discussions: In Figure 4, between time t0 and time t1, part ofip(t) is transformed to is(t) by CTEH. When is(t) charges up the capacitorC, the voltage vs(t) is generated and rectified, forming the output voltageUo. The time period from t0 ′ to t0 is corresponding to the magnetizationprocess from point b′ to point a′ in Figure 2. The variation of magneticfield B ( = Bs − Br) is so small that the induced voltage vs(t) is verylow and the is(t) is almost negligible.In order to investigate the CTEH capacity in the range of the largecurrent variation, the Cobalt-based magnetic core is replaced by a Su-permendur core in Figure 1, which size is 46 mm × 36 mm × 6.5 mm,and other parameters are not changed. When the current ip(t) is variedfrom 1 to 1000 A, the experimental results are shown in Figure 5.When the CTEH is loaded with a pure resistive load RL without thecapacitor C, the output voltage Uo (mV) (left y-axis in Figure 5) can bestably settled down to about 900 mV while the current ip(t) increasesfrom 150 to 1000 A. The continuous and relatively stable output voltagecan be described by Equation (4). Subsequently, RL is set to 15 k and706 ELECTRONICS LETTERS August 2022 Vol. 58 No. 18 wileyonlinelibrary.com/iet-el 1350911x, 2022, 18, Downloaded from https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/ell2.12566 by CochraneItalia, Wiley Online Library on [11/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons LicenseFig. 5 CTEH with the primary current changing in a large rangeconnected with the shunt capacitor C to form the filter, the output voltageUo (V) (right y-axis in Figure 5) can be stabilized to a value of around15 V. When RL is set to 220  as the low power load, Uo (right y-axisin Figure 5) can be stabilized to a value of about 10 V, giving rise to apower output of 0.5 W.Conclusion: This paper proposes a novel CTEH based on a saturablemagnetic core, which can generate stable output power in the wide-range current of the transmission line. The stable output power of theCTEH is illustrated by the constant voltage–time product with its sat-urable magnetization characteristic and proved by the experiment withthe resistive load in the primary side current of the CTEH’s increasingfrom 1 to 1000 A. Also, the maximum power on the load can reach about0.5 W.Conflict of interest: The authors declare that they have no known com-peting financial interests or personal relationships that could have ap-peared to influence the work reported in this paper.Funding information: This submission is not supported by funding.Data availability statementt: The data that supports the findings of thisstudy are available in the supplementary material of this article© 2022 The Authors. Electronics Letters published by John Wiley &Sons Ltd on behalf of The Institution of Engineering and Technology.This is an open access article under the terms of the Creative CommonsAttribution License, which permits use, distribution and reproduction inany medium, provided the original work is properly cited.Received: 8 May 2022 Accepted: 20 June 2022doi: 10.1049/ell2.12566References1 Qian, Z.: Power supply for high voltage circuit of active electronic currenttransformer. High Voltage Appar. 40(2), 135–138 (2004)2 Zangl, H., Bretterklieber, T., Brasseur, G.: A feasibility study on au-tonomous online condition monitoring of high-voltage overhead powerlines. IEEE Trans. Instrum. Meas. 58(5), 1789–1796 (2009). https://doi.org/10.1109/tim.2009.20129433 Chi, T., Yanzhen, Z., Zijian, T.: Study on energy harvesting of open-closecurrent transformer. In: ICSMD2020, Xi’an, China, 15–17 Oct (2020),pp. 567–571. https://doi.org/10.1109/icsmd50554.2020.92616724 Gorchakov, A. V., Rashitov, P. A.: High-efficiency power supply fordistributed flexible alternative current transmission system devices. In:REEPE, Moscow, Russia, 14–15 March (2019). https://doi.org/10.1109/reepe.2019.87088435 Jinhua, W., Jaehoon, K., Dong Sam, H.: Powerline energy harvesting cir-cuit with a desaturation controller for a magnetic core. In: MWSCAS,Lansing, MI, USA, 9–11 Aug (2021) pp. 220–223. https://doi.org/10.1109/mwscas47672.2021.95318906 Wen, Z., Zhengyang, L., Qinqing, H., Yi, J., Zihan, C.: Design ofmagnetic cores for current transformer energy harvesting devices. In:APPEEC, Macau, China, 1–4 Dec (2019), p. 5. https://doi.org/10.1109/appeec45492.2019.89948097 Wang, J., Chen, W.: Output characteristics analysis of energy harvest-ing current transformer. IEEE Sens. J. 21(20), 22595–22602 (2021).https://doi.org/10.1109/jsen.2021.31078648 Li, P.: The influence factors of CT output performance for power trans-mission cables. Electomech. Components 10, 41(5), 53–60 (2021)ELECTRONICS LETTERS August 2022 Vol. 58 No. 18 wileyonlinelibrary.com/iet-el 707 1350911x, 2022, 18, Downloaded from https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/ell2.12566 by CochraneItalia, Wiley Online Library on [11/01/2023]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons License

A current transformer energy harvester with stable output based on the saturable magnetic core

https://iris.polito.it/bitstream/11583/2974498/1/55-A%20current%20transformer%20energy%20harvester%20with%20stable%20output%20based%20on%20the%20saturable%20magnetic%20core.pdf

A current transformer energy harvester with stable output based on the saturable magnetic core

Abstract

Similar works

Full text

Available Versions

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)