22 results found
Pucci N, Arteaga JM, Kwan CH, et al., 2021, A 13.56 MHz bidirectional IPT system with wirelessly synchronised transceivers for ultra-low coupling operation, 2021 IEEE Energy Conversion Congress and Exposition (ECCE), Publisher: IEEE, Pages: 5781-5787
This paper presents a high-frequency inductive power transfer (HF-IPT) system with bidirectional capability employing a new wireless synchronisation method. Synchronisation is achieved by transmitting a reference ultra high frequency tone (433.92 MHz) that is stepped down to 13.56 MHz in each transceiver. This allows the operating frequency to be locked across the two sides of the system. Afterwards, a phase search is performed looking for maximum power throughput, determining the phase at the point of resonance (i.e., no reflected reactances). The experimental implementation is achieved with two back-to-back Class EF coil-drivers driven by independent synchronisation circuits. In the experimental setup a constant input voltage is set for each of the two coil-drivers by implementing a source-sink configuration, emulating a bidirectional DC-DC conversion stage at each side. Experimental results show successful transceiver synchronisation, and 4 W were transferred from one end to the other and conversely at an ultra-low coupling of 1.6%. This proves that the combination of the load-independent Class EF transceivers and the synchronisation technique introduced herein is suitable for applications that require large tolerance to misalignment and air gaps larger than one coil diameter, such as in micro e-mobility.
Pucci N, Arteaga JM, Kwan C, et al., 2021, Induced voltage estimation from class EF switching harmonics in HF-IPT systems, IEEE Transactions on Power Electronics, Vol: 37, Pages: 4903-4916, ISSN: 0885-8993
One of the advantages of high-frequency inductive power transfer systems is the high tolerance to misalignment and large air-gaps. However, the inherently large magnetic field volumes can lead to coupling of additional foreign objects with the primary, causing possible detuning of the system and heating of the objects. These foreign objects and the conditions of the local environment can load the transmitter, which changes the induced voltage on the primary side. Unfortunately, the induced voltage is not directly measurable in an operating transmitter and the most straightforward way of calculating this variable, through a measurement of primary coil current and voltage, can cause a significant decrease in quality factor which reduces system performance. An integrated solution capable of estimating the induced voltage through other less invasive measurements in the primary is needed to ensure safety of operation through foreign object detection. Knowledge of the induced voltage can also be used to correct tuning mismatches where both sides of the link are active (i.e., in synchronous rectification and bidirectional systems). In this article, multiple candidate variables for estimating the induced voltage are assessed based on factors such as measurement practicality and estimation accuracy. It is demonstrated for the first time that a solution which is based on the measurement of only two variables, the amplitude of the fundamental frequency of the switching waveform and input current, can achieve state-of-the-art induced voltage estimation accuracy. These two variables, which can be obtained using simple cost-effective analogue circuitry, are used in a Gaussian process to generate a regression model. This is used to estimate induced voltages at any angle in an approximate magnitude range of 0–20 V with a normalized root-mean-square error of 1% for the real part and 1.5% for the imaginary part. This corresponds to detecting a plastic container with 1 kg of sal
Arteaga JM, Kwan CH, Nikiforidis I, et al., 2021, Design of a one-to-four isolated DC-DC converter using a 13.56 MHz resonant air-core transformer, 2021 IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 2580-2585
This paper showcases the design and development of a DC-DC converter with one input and four outputs using a high frequency resonant air-core transformer. The transmitter to receivers air-gap is 25 mm. Practical tuning equations were derived for multiple receivers which allow the converter to be optimised for overall efficiency and unity power factor at the transmit coil (i.e. zero reflected reactance). Experiments were conducted using two receive coil structures, one with four equally shaped adjacent coils in a single PCB, and the other with four differently-shaped coils featuring overlapping traces to maximise the coupling factor with the transmitter and minimise the coupling factor between the receivers. The two structures were tested and compared using the same transmitter, driven by a single-ended 13.56 MHz Class EF inverter. Single-ended Class D rectifiers were implemented at the receive side. Experiments were performed, first with equal AC test loads, and afterwards with the addition of the rectifiers and buck converters to regulate each of the four output voltages to 15 V independently. The results of the experiments implementing adjacent coils demonstrate that equal distribution of power can be achieved by modifying the tuning capacitances at the receivers with the AC loads; however, when the voltage-regulating buck converters were introduced at each output, it was only with the coil structure with overlapping traces that the required power of 10 W at each output was achieved.
Kwan CH, Arteaga JM, Pucci N, et al., 2021, A 110 W E-scooter Wireless Charger Operating at 6.78 MHz with Ferrite Shielding, IEEE Wireless Power Week (WPW) / IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW), Publisher: IEEE
Kwan C, Arteaga Saenz J, Aldhaher S, et al., 2020, A 600W 6.78MHz wireless charger for an electric scooter, IEEE PELS WoW 2020, Publisher: IEEE, Pages: 278-282
This paper presents a 600 W electric scooter wireless charging solution operating at a frequency of 6.78 MHz. At the transmitter end, a load-independent Class EF push-pull(differential) inverter with GaN transistors was used to drive a 33 cm square-shaped copper pipe coil. A full-wave voltage-triplerClass D rectifier with silicon Schottky diodes was connected to a24 cm-by-26 cm trapezoidal receiver coil (also made of copperpipe) mounted underneath the steel frame of the scooter. In order to reduce the eddy current and magnetic losses in the steel chassis, parts of the electric scooter frame were shielded with copper tape. With the battery recharging in situ at 600 W,the IPT system achieved a DC-to-DC efficiency of 84 %.
Lan L, Kwan CH, Arteaga JM, et al., 2020, A 100W 6.78MHz inductive power transfer system for drones, 2020 14th European Conference on Antennas and Propagation (EuCAP), Publisher: IEEE, Pages: 1-4
This paper reports on the design and development of a wireless charging solution for a DJI Matrice 100 quadcopter drone. The system is based on a high frequency inductive power transfer system built with lightweight copper pipe air-core coils at both ends and lightweight electronics at the receive side. The developed system is capable of delivering power to the drone at the same rate as the original wired charger (100W) when landed at any position on the charging pad, regardless of the lateral misalignment or angular orientation. The charging pad is circular with a one-metre diameter, therefore allowing for a lateral misalignment of up to 25cm. The system has an average mains-to-battery efficiency of 70% and enables the drone missions to be completely autonomous as it eliminates the need for human interference for battery recharging or swapping.
Arteaga Saenz JM, Lan L, Kwan CH, et al., 2020, Characterisation of high frequency inductive power transfer receivers using pattern recognition on the transmit side waveforms, IEEE Applied Power Electronics Conference and Exposition (APEC), Publisher: IEEE, Pages: 825-831, ISSN: 1048-2334
This paper demonstrates the characterisation of inductively coupled receivers for high frequency inductive power transfer (HF-IPT) systems using pattern recognition on the inverter waveforms at the transmit side. The impedance reflected by the candidate receivers to the transmit coil was estimated using a model programmed to associate the experimental drain-voltage waveforms of the inverter when it drives a receiver under test to those when driving known loads. The necessity of employing this technique is due to the difficulty of accurately measuring current and voltage across the coil given the parasitic effects of probing and the precise skewing required to measure an impedance, especially at high Q-factor. The proposed technique is convenient for characterising and comparing the impedance reflected by candidate receivers for a particular application where there is a choice to be made with respect to the rectifier topologies and semiconductor technologies. Experimental results, using a 13.56 MHz 100 W inductive power transfer system, were obtained for a full-wave Class D rectifier using silicon (Si) and silicon carbide (SiC) Schottky diodes, and two Class E rectifiers using SiC diodes.
Pucci N, Kwan CH, Yates DC, et al., 2020, Multi-megahertz IPT systems for biomedical devices applications, 19th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (Power MEMS), Publisher: IEEE, Pages: 1-7
This paper investigates the main design constraints for the optimisation of an inductive power transfer (IPT) link for recharging implantable medical devices , and presents the potential advantages of operating in the multi-MHz range for such applications. The design proposed in this paper offers a fast charging solution, allowing patients to recharge their active medical implants every 4-5 years for 40% of its battery capability. The main challenge consists of obtaining good coupling and effective Q factor of the receiver coil, while minimizing the overall increase in size of the medical implant. Analysis obtained through electromagnetic simulations with CST Studio Suite for a 13.56 MHz, 1 W system suggests that it is possible to achieve a relatively high theoretical link efficiency of 66%, while keeping surface temperature increases and specific absorption rate (SAR) within the limits established in EN 45502  and ICNIRP 1998 . The experimental results show two feasible systems with different separation distances between the device's metallic case and the receiver coil, achieving transfer efficiencies  of 41% and 53% for separations of 1 mm and 7 mm, respectively.
Nikiforidis I, Arteaga JM, Kwan CH, et al., 2020, Design and modelling of class EF inverters for wireless power transfer applications, 19th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (Power MEMS), Publisher: IEEE, Pages: 1-4
Class EF inverters have been widely used recently as primary coil drivers for wireless power transfer applications since they achieve constant output current across a range of link coupling factor values. As the operating frequency that the inductive link is tuned at increases the traditional circuit design techniques that are based on first order calculations fail to represent the inverter behaviour accurately. In this paper, we present a novel method of modelling Class EF inverters that is based on state space representation of the circuit and thus providing the highest accuracy possible. Our method consists of a combination of analytical and numerical calculations in such manner that any parasitic component of the circuit, such as the nonlinear output capacitance of a power switch, can be included in the tuning process.
Pucci N, Kwan CH, Yates DC, et al., 2020, Effect of fields generated through wireless power transfer on implantable biomedical devices, 2019 IEEE PELS Workshop on Emerging Technologies: Wireless Power Transfer (WoW), Publisher: IEEE, Pages: 1-5
This paper assesses the safety of pacemakers when exposed to the electromagnetic (EM) field generated by high frequency inductive power transfer (HF-IPT) systems. It includes both simulation and experimental results, showing temperature variations to ensure conformity with the EN standards, changes in detected lead impedance and determining whether EM field strength can affect the operating mode of the device. This is the first time the interaction between 6.78MHz, 100W HF-IPT systems and pacemaker devices was tested up to distances of 5 cm to 10 cm, Temporary decrease of detected lead's impedance and interruption of communications are the most relevant effects recorded through in-vitro tests. No permanent alteration of the device's operation was recorded, indicating good early stage evidence of safety for pacemaker users in proximity of this new emerging technology.
Calderon-Lopez G, Todd R, Forsyth AJ, et al., 2020, Towards Lightweight Magnetic Components for Converters with Wide-bandgap Devices, IEEE 9th International Power Electronics and Motion Control Conference (IPEMC-ECCE Asia), Publisher: IEEE, Pages: 3149-3155
Lan L, Polonelli T, Qin Y, et al., 2020, An Induction-Based Localisation Technique for Wirelessly Charged Drones, IEEE PELS Workshop on Emerging Technologies - Wireless Power Transfer (WoW) / IEEE Wireless Power Week (WPW) / IEEE MTT-S Wireless Power Transfer Conference (WPTC), Publisher: IEEE, Pages: 275-277
Arteaga Saenz J, Aldhaher S, Kkelis G, et al., 2019, Dynamic capabilities of multi-MHz inductive power transfer systems demonstrated with batteryless drones, IEEE Transactions on Power Electronics, Vol: 34, Pages: 5093-5104, ISSN: 0885-8993
This paper presents the design of a multi-MHz inductive power transfer (IPT) system showcasing lightweight and energy-efficient solutions for non-radiative wireless power transfer. A proof of concept is developed by powering a drone without a battery that can hover freely in proximity to an IPT transmitter. The most challenging aspect, addressed here for the first time, is the complete system level design to provide uninterrupted power-flow efficiently while allowing for variable power demand and highly variable coupling factor. The proposed solution includes the design of lightweight air-core coils that can achieve sufficient coupling without degrading the aerodynamics of the drone, and designing newly-developed resonant power converters at both ends of the system. At the transmittingend, a load-independent Class EF inverter, which can drive a transmitting-coil with constant current amplitude and achieves zero-voltage switching (ZVS) for the entire range of operation, was developed; and at the receiving-end, a hybrid Class E rectifier, which allows tuning for large changes in coupling and power demand, was used. For the demo, the range of motion of the drone was limited by a 7.5 cm nylon string tether, connected between the centre of the transmitting-coil and the bottom of the drone. The design of the IPT system, including all the power conversion stages and the IPT link, is explained in detail. The results on performance and specific practical considerations required for the physical implementation are provided. An average end-to-end efficiency of 60% was achieved for a coupling range of 23% to 5.8%. Relevant simulations concerning human exposure to electromagnetic fields are also included to assure that the demo is safe according to the relevant guidelines. This paper is accompanied by a video featuring the proposed IPT system.
Kwan CH, Yates DC, Mitcheson PD, 2019, Reducing human body heating and temperature rises due to inductively-powered implantable medical devices, 18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications, Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
Kwan CH, Arteaga JM, Yates DC, et al., 2019, Design and Construction of a 100W Wireless Charger for an E-Scooter at 6.78MHz, IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW) / Wireless Power Week Conference, Publisher: IEEE, Pages: 186-190
Pucci N, Kwan CH, Yates DC, et al., 2019, Effect of Fields Generated Through Wireless Power Transfer on Implantable Biomedical Devices, IEEE MTT-S Wireless Power Transfer Conference (WPTC) / IEEE PELS Workshop on Emerging Technologies - Wireless Power (WoW) / Wireless Power Week Conference, Publisher: IEEE, Pages: 160-164
Lan L, Ting NM, Aldhaher S, et al., 2018, Foreign Object Detection for Wireless Power Transfer, 2nd URSI Atlantic Radio Science Meeting (AT-RASC), Publisher: IEEE
This paper presents foreign object detection (FOD) methods for MHz wireless power transfer (WPT) systems. Unlike current FOD implementations, the presented methods can operate without requiring a feedback loop from the wireless power receiver to the transmitter. This allows complete decoupling of the transmitter and receiver and therefore reduces the design complexity and cost of the system. The developed FOD methods were implemented on a 13.56 MHz WPT and experimental results are presented showing successful detection of a wide range of objects regardless of the loading condition of the system.
Kwan CH, Pinuela M, Mitcheson P, et al., 2016, Inductive power transfer system, WO2016050633 A3
There is provided a near-field inductive power transfer system (10), comprising a power transmission device (100) arranged to transmit power wirelessly at a first frequency, f0, and a power reception device (200) arranged to receive power transmitted by the power transmission device (100). The power reception device (200) is moveable relative to the power transmission device (100) and comprises a receiver circuit (210) configured to receive power for powering a variable load (230) when the power reception device (200) is in a near-field region of the power transmission device (100), the receiver circuit being a resonant circuit with a resonant frequency, fR, such that 0.2 < f0/fR < 3. The power reception device (200) also includes an impedance emulator (220) for providing the received power to the variable load (230), the impedance emulator being arranged to suppress a variation in an impedance presented to the receiver circuit (210) by the load when the load varies during use of the near-field inductive power transfer system (10).
Plazzotta G, Kwan C, Boyd M, et al., 2016, Effects of memory on the shapes of simple outbreak trees, Scientific Reports, Vol: 6, ISSN: 2045-2322
Genomic tools, including phylogenetic trees derived from sequence data, are increasingly used to understand outbreaks of infectious diseases. One challenge is to link phylogenetic trees to patterns of transmission. Particularly in bacteria that cause chronic infections, this inference is a ected by variable infectious periods and infectivity over time. It is known that non-exponential infectious periods can have substantial e ects on pathogens' transmission dynamics. Here we ask how this non-Markovian nature of an outbreak process a ects the branching trees describing that process, with particular focus on tree shapes. We simulate Crump-Mode-Jagers branching processes and compare di erent patterns of infectivity over time. We nd that memory (non-Markovian-ness) in the process can have a pronounced e ect on the shapes of the outbreak's branching pattern. However, memory also has a pronounced e ect on the sizes of the trees, even when the duration of the simulation is xed. When the sizes of the trees are constrained to a constant value, memory in our processes has little direct e ect on tree shapes, but can bias inference of the birth rate from trees. We compare simulated branching trees to phylogenetic trees from an outbreak of tuberculosis in Canada, and discuss the relevance of memory to this dataset.
Kwan CH, Yates DC, Mitcheson PD, 2016, Design Objectives and Power Limitations of Human Implantable Wireless Power Transfer Systems, IEEE Wireless Power Transfer Conference (WPTC), Publisher: IEEE, ISSN: 2474-0225
Kwan CH, Kkelis G, Aldhaher S, et al., 2015, Link efficiency-led design of mid-range inductive power transfer systems, Pages: 1-7
Kwan CH, Lawson J, Yates DC, et al., 2014, Position-insensitive long range inductive power transfer, 14th International Conference on Micro- and Nano-Technology for Power Generation and Energy Conversion Applications (PowerMEMS), Publisher: IOP PUBLISHING LTD, ISSN: 1742-6588
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