Browsing by Author "Liu, Yining"

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    Cylindrical Transmitting Coil for Two-Dimensional Omnidirectional Wireless Power Transfer
    (IEEE, 2022-10) Ha, Nam Van; Liu, Yining; Jayathurathnage, Prasad Kumara Sampath; Simovski, Constantin; Tretyakov, Sergei; Department of Electronics and Nanoengineering; Sergei Tretiakov Group; Kostantin Simovski Group
    Megahertz-range wireless power transfer has become a promising approach for increasing spatial freedom of charging. This paper proposes a cylindrical-shaped coil, which can produce the homogeneous magnetic field in a plane. The coil consists of two helical windings, which are wound to guide the current in opposite directions. A single power source is used to excite the transmitter without any current amplitude or phase control circuits. Furthermore, since the parasitic capacitance of the coil is not negligible due to the complexity of the coil shape, we develop a general equivalent model with parasitic capacitance for the analysis of complex coils. The system efficiency of the proposed omnidirectional wireless power transfer device is validated by a practical experiment. The measured DC-to-DC efficiency of approximately 72.4% and the load power of 13 W are demonstrated for the proposed wireless charging system at 6.78 MHz operating frequency. Finally, we verify that the electromagnetic exposure satisfies the safety regulations.
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    Design and Performance Analysis of a Repeater-Assisted, Multi-Receiver Wireless Power Transfer System Operating At MHz Frequencies
    (IEEE, 2024) Liu, Yining; Ha-Van, Nam; Jayathurathnage, Prasad; Kyyra, Jorma; Tretyakov, Sergei A.; Department of Electrical Engineering and Automation; Department of Electronics and Nanoengineering; Industrial and Power Electronics; Sergei Tretiakov Group
    Simultaneous wireless power transfer (WPT) to multiple receivers (Rxs) is an important requirement for wireless charging of consumer electronic devices. In this article, we propose a WPT coil structure capable of achieving independent multi-Rx WPT with a confined and uniform rotating magnetic field at megahertz operating frequencies. Compared with the existing multiple receiver WPT structures, the proposed structure exhibits low leakage flux outside the power transmitter. Thanks to the single-coil transmitter structure and the load-independent current feature in the repeater coil, no additional control circuit is needed to obtain independent power transfer to multiple receiver devices. The proposed solution is experimentally demonstrated in a 6.78-MHz 80-W WPT prototype, with a dc-to-dc efficiency of 90.2 % in the full-load case using four 20-W receiver circuits.
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    Design of contemporary Buddhist multipurpose hall in Han-nation area of China
    (2019) Liu, Yining; Nieto, Fernando; Department of Architecture; Arkkitehtuurin laitos; Taiteiden ja suunnittelun korkeakoulu; School of Arts, Design and Architecture; Sanaksenaho, Pirjo
    Due to the revival of Buddhism, the increasing number of Buddhists and the prosperity of the tourism-related activities, traditional Buddhist architectures in Han-nation areas nowadays suffer a lot from evident shortcomings such as excessive pursuit of ancient style, lack of features, non-suitable for the requirements of modern Buddhism and so on. In order to meet the actual needs of modern Buddhist temples, this paper studies the evolution of architectural planning and design of Buddhist temples to meet the habits of Buddhists and the relations with the modern society. This paper also discusses the design of Buddhism buildings by analyzing related projects in Taiwan(China) and Japan. Buddhism architectural theory and practice policy mainly focuses on functional layout and corresponding architectural design. After that, it provides a practical design solution of Buddhist multipurpose space in Harbin, China, exploring the innovation of modern Buddhist architecture with Chinese characteristics, and the cultural significance of Buddhism that integrated with modern architecture theory. There is an interview of a monk in Chapter three about the design project.
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    Lightweight Privacy-preserving Raw Data Publishing Scheme
    (IEEE Computer Society, 2021-12) Chen, Jingxue; Liu, Gao; Liu, Yining; Department of Communications and Networking; Guilin University of Electronic Technology
    Data publishing or data sharing is an important part of analyzing network environments and improving the Quality of Service (QoS) in the Internet of Things (IoT). In order to stimulate data providers (i.e., IoT end-users) to contribute their data, privacy requirement is necessary when data is collected and published. In traditional privacy preservation techniques, such as k-anonymity, data aggregation and differential privacy, data is modified, aggregated, or added noise, the utility of the published data are reduced. Privacy-preserving raw data publishing is a more valuable solution, and nn-source anonymity based raw data collection is most promising by delinking raw data and their sources. In this article, a lightweight raw data collection scheme for publishing is proposed, in which the rawness and the unlinkability of published data are all really guaranteed with Shamir's secret sharing, and shuffling algorithm. Moreover, it is lightweight and practical for the IoT environment by the performance evaluation.
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    A new Push-pull Class-Φ Converter for Multi-MHz Dual-frequency Wireless Power Transfer Applications
    (2023) Liu, Yining; Jayathurathnage, Prasad; Tretyakov, Sergei A.; Kyyrä, Jorma; Department of Electrical Engineering and Automation; Department of Electronics and Nanoengineering; Industrial and Power Electronics; Sergei Tretiakov Group
    We propose a novel converter for simultaneous dual-frequency wireless power transfer (WPT) devices. The proposed converter realizes independent WPT channels at two frequencies: the main frequency fs and the second harmonic 2fs. With the coupled-T-network, a new class-Φ based push-pull inverter is introduced to provide load-independent currents for two transmitter coils. The power channels at two frequencies are decoupled and independent from each other, providing high flexibility for individual or simultaneous WPT at both frequency bands. The experimental WPT system has verified the characteristics of the proposed converter, realizing 64 W: 16 W power transfer for 6.78 MHz and 13.56 MHz receivers, respectively, with 80 % system efficiency.
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    A New Simplified Method and Design Guidelines for the Optimization of Push-Pull Class Φ 2Converters for Wireless Power Transfer Applications
    (IEEE, 2023-08-01) Liu, Yining; Jayathurathnage, Prasad; Kyyra, Jorma; Department of Electrical Engineering and Automation; Industrial and Power Electronics
    The complicated resonant operations of class Φ2 topology bring challenges for accurate design and performance optimization, hindering the full utilization potential of converters. Considering the narrow design freedom in traditional methods with almost fixed duty cycle D, this article widens the design options of push-pull class Φ2 converters through frequency-harmonic analysis. A full selection freedom of Din (0,0.5) is discussed analytically, providing ample space for optimization based on any required performance indices. From 1.98E5 analytical results, we found six numerical equations that fully decouple the interconnected relations between each circuit parameter and D. The proposed numerical method allows rapid circuit design and component selection with a high accuracy regardless of the system power or load voltage. Parasitic effects are discussed and incorporated into the design approach as correction steps. Finally, we introduce performance analysis based on an example wireless power transfer (WPT) system, providing in-depth studies on the optimization regarding efficiency, power output capability, and component selection. Experimental results validate the accuracy and efficiency of the proposed design method based on a 100-W WPT system at 6.78 MHz frequency. Both inverter and rectifier present load-independent soft-switching operations, with converter efficiency over 93%. The system provides 83% dc-dc efficiency at full load.
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    Non-Coherent Power Combining for Self-Tuning Omnidirectional Wireless Power Transfer
    (2023) Liu, Yining; Ha-Van, Nam; Jayathurathnage, Prasad; Kyyrä, Jorma; Tretiakov, Sergei A.; Department of Electrical Engineering and Automation; Department of Electronics and Nanoengineering; Industrial and Power Electronics; Sergei Tretiakov Group
    This paper introduces a new method for realizing truly omnidirectional WPT without using any active control. The proposed method uses non-coherent feeds for two or more transmitting antennas, which ensures absence of any blind spots for power reception around the transmitting device. We provide analytical insights, supported by simulations and experiments, to validate our approach.
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    Noncoherent Power Combining for Free-Positioning Wireless Power Transfer in Large Area
    (IEEE, 2024) Liu, Yining; Al Mahmud, Shamsul Arefeen; Ha-Van, Nam; Jayathurathnage, Prasad; Kyyra, Jorma; Tretyakov, Sergei A.; Department of Electrical Engineering and Automation; Department of Electronics and Nanoengineering; Industrial and Power Electronics; Sergei Tretiakov Group
    In this article, we propose a new coil-energizing method for multitransmitter (Tx) wireless power transfer (WPT) systems that enable complete freedom of receiver (Rx) positioning in a large area. The principle is based on noncoherent power combining, where multiple Tx coils are supplied in a predefined pattern by mixing two slightly different frequencies and four different phase angles. The powers delivered from Tx coils at two frequencies are then combined incoherently at the Rx side, resulting in full positional and rotational freedom for the Rx charging. The power transfer blind spots in conventional WPT systems are completely eliminated with the proposed noncoherent power combining method due to its natural robustness against cancelations. The experimental setup shows constant dc-dc power transfer efficiency around 90% for arbitrary Rx movements without any further requirements on dynamic controls of Txs or Rxs other than the simplest activation/deactivation.
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    Parameter tuning method for class Φ2converters for high-frequency wireless power transfer applications
    (2022) Liu, Yining; Jayathurathnage, Prasad; Kyyra, Jorma; Department of Electrical Engineering and Automation; Department of Electronics and Nanoengineering; Industrial and Power Electronics; Sergei Tretiakov Group
    This paper presents a method to compensate detuning of class Φ2 push-pull converters due to practical disparities such as component values tolerances, parasitic effects, and manufacturing errors. A simple and effective tuning method is proposed based on only four steps. An example 100 W, 6.78 MHz wireless power transfer system is presented, that reaches 82.3% efficiency after tuning using the proposed method.
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    Self-Decoupled and Integrated Coils for Modular Multi-Transmitter Wireless Power Transfer Systems
    (IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2022-11) Jayathurathnage, Prasad; Liu, Yining; Kyyra, Jorma; Department of Electronics and Nanoengineering; Department of Electrical Engineering and Automation; Sergei Tretiakov Group; Industrial and Power Electronics
    The use of multiple transmitters (Tx) has been an attractive solution for enabling free-positioning wireless power transfer (WPT) in a large area. One of the key challenges in such multi-Tx WPT systems is the cross-coupling between Tx coils. This letter proposes a compact self-decoupled Tx coil solution for multi-Tx WPT systems. The measured cross-coupling between Tx coils has been reduced by 95% compared to conventional coil designs. Additionally, an integration method for a compensation inductor with the main Tx coil is proposed. Therefore, the coil design proposed in this letter facilitates creation of fully modular and scalable Tx coils for multi-Tx WPT systems. The proposed designs are experimentally verified in a laboratory prototype.