Starting from Tesla's principles of wireless power transfer a century ago, this critical review o... more Starting from Tesla's principles of wireless power transfer a century ago, this critical review outlines recent magnetoinductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load. Index Terms-Electromagnetic fields, human exposure, maximum efficiency, maximum power transfer, mid-range wireless power transfer, tesla's resonators.
ABSTRACT These keynotes speeches the following: Keynote speech on “Challenges of modern power sys... more ABSTRACT These keynotes speeches the following: Keynote speech on “Challenges of modern power systems and IEEE PES”; Plenary Session on “Challenges and Opportunities of Smart Grid Development and Technologies”; The Technical Challenges and Benefits of Implementing AMI in Hong Kong; Smart Grid Features of Energy Management System &amp; Distribution Management System of HK Electric; Electric Springs - A New Smart Grid Technology for Taming the Intermittent Nature of Wind and Solar Power; Challenges and Opportunities of Distributed Energy Resource Integration; Honorary Lecture (Free-of-charge); Outdoor Insulator Flashover Problems under Icing Conditions.
With the increasing adoption of renewable energy sources into power grids, the issue of voltage a... more With the increasing adoption of renewable energy sources into power grids, the issue of voltage and frequency fluctuation of the network becomes a more critical problem that needs to be resolved urgently. The so-called demand-side management (DSM) of power system provides the opportunity for the prospective grids to intelligently balance the power supply and consumption. As one of the crucial roles of DSM, smart loads are naturally committed to manage the power flow of the network. Other than previous communication-based smart loads, the recently proposed electric springs (ES) provide an opportunity to turn some conventional loads into smart loads without the need for communication. In this paper, a simple voltage and frequency (v&f) control method is applied to such a smart load for tackling the voltage and frequency fluctuations of the power grids. Simulation results reveal that with the proposed v&f control, the smart load can achieve better voltage and frequency regulation performance than that with the conventional control and smart load. Experimental results validating the feasibility of the proposed v&f controller on regulating the voltage amplitude and frequency of the common-coupling point of a power grid are provided.
ABSTRACT In this paper, we present a brief overview of historical developments of wireless power ... more ABSTRACT In this paper, we present a brief overview of historical developments of wireless power and an analysis on the use of Teslas resonators in domino forms for wireless power transfer. Relay resonators are spaced between the transmitter coil and the receiver coil with the objectives of maximizing energy efficiency and increasing the overall transmission distance between the power source and the load. Analytical expressions for the optimal load and maximum efficiency at resonance frequency are derived. These equations are verified with practical measurements obtained from both coaxial and non-coaxial domino-resonator systems. To avoid the use of high operating frequency for wireless power transfer in previous related research, the technique presented here can be used at sub-Mega-Hertz operation so as to minimize the power loss in both the power supply and the output stage. We demonstrated both theoretically and practically that unequal-spacing for the coaxial straight domino systems has better efficiency performance than equal-spacing method. Also, the flexibility of using resonators in various domino forms is demonstrated.
ABSTRACT A new design of low-cost and low-profile power transformer is presented in this paper. T... more ABSTRACT A new design of low-cost and low-profile power transformer is presented in this paper. The manufacturing cost of a power transformer can be reduced using the proposed printed-circuit board (PCB) transformer. The transformer windings are etched on the opposite sides of a double-sided PCB. Self-adhesive ferrite polymer composite (FPC) sheets are stuck on the two PCB surfaces to shield the magnetic flux induced from the transformer windings. The PCB transformer does not require manual winding and bobbin. A power converter prototype employing the PCB transformer has been implemented. The technique of choosing the optimum switching frequency of the power converter using PCB transformer is addressed in this paper. The maximum power delivered from the prototype is 94 W. The maximum efficiency of the power converter is 83.5%
IEEE Journal of Emerging and Selected Topics in Power Electronics, Jun 1, 2020
With the electric spring (ES) being practically evaluated by utility companies in power grids, th... more With the electric spring (ES) being practically evaluated by utility companies in power grids, there is a need to explore its practical implementation aspects of general applications. In this paper, we propose three interior angle control principles for the ES. Systematic analysis and comparative study show that these three control principles lead to different smart load (SL) performance. The operating characteristic curves and distinctive features/advantages of the SL using these three control methods are analyzed and explained. A generalized controller structure suitable for the implementations of all these three angle control schemes is presented. It is practically shown that the same controller structure can be programmed to implement these three angle control strategies. This outcome is the first step to realize a programmable ES-based SL for providing multiple functions.
Starting from Tesla's principles of wireless power transfer a century ago, this critical review o... more Starting from Tesla's principles of wireless power transfer a century ago, this critical review outlines recent magnetoinductive research activities on wireless power transfer with the transmission distance greater than the transmitter coil dimension. It summarizes the operating principles of a range of wireless power research into 1) the maximum power transfer and 2) the maximum energy efficiency principles. The differences and the implications of these two approaches are explained in terms of their energy efficiency and transmission distance capabilities. The differences between the system energy efficiency and the transmission efficiency are also highlighted. The review covers the two-coil systems, the four-coil systems, the systems with relay resonators and the wireless domino-resonator systems. Related issues including human exposure issues and reduction of winding resistance are also addressed. The review suggests that the use of the maximum energy efficiency principle in the two-coil systems is suitable for short-range rather than mid-range applications, the use of the maximum power transfer principle in the four-coil systems is good for maximizing the transmission distance, but is under a restricted system energy efficiency (<50%); the use of the maximum energy efficiency principle in relay or domino systems may offer a good compromise for good system energy efficiency and transmission distance on the condition that relay resonators can be placed between the power source and the load. Index Terms-Electromagnetic fields, human exposure, maximum efficiency, maximum power transfer, mid-range wireless power transfer, tesla's resonators.
ABSTRACT These keynotes speeches the following: Keynote speech on “Challenges of modern power sys... more ABSTRACT These keynotes speeches the following: Keynote speech on “Challenges of modern power systems and IEEE PES”; Plenary Session on “Challenges and Opportunities of Smart Grid Development and Technologies”; The Technical Challenges and Benefits of Implementing AMI in Hong Kong; Smart Grid Features of Energy Management System &amp; Distribution Management System of HK Electric; Electric Springs - A New Smart Grid Technology for Taming the Intermittent Nature of Wind and Solar Power; Challenges and Opportunities of Distributed Energy Resource Integration; Honorary Lecture (Free-of-charge); Outdoor Insulator Flashover Problems under Icing Conditions.
With the increasing adoption of renewable energy sources into power grids, the issue of voltage a... more With the increasing adoption of renewable energy sources into power grids, the issue of voltage and frequency fluctuation of the network becomes a more critical problem that needs to be resolved urgently. The so-called demand-side management (DSM) of power system provides the opportunity for the prospective grids to intelligently balance the power supply and consumption. As one of the crucial roles of DSM, smart loads are naturally committed to manage the power flow of the network. Other than previous communication-based smart loads, the recently proposed electric springs (ES) provide an opportunity to turn some conventional loads into smart loads without the need for communication. In this paper, a simple voltage and frequency (v&f) control method is applied to such a smart load for tackling the voltage and frequency fluctuations of the power grids. Simulation results reveal that with the proposed v&f control, the smart load can achieve better voltage and frequency regulation performance than that with the conventional control and smart load. Experimental results validating the feasibility of the proposed v&f controller on regulating the voltage amplitude and frequency of the common-coupling point of a power grid are provided.
ABSTRACT In this paper, we present a brief overview of historical developments of wireless power ... more ABSTRACT In this paper, we present a brief overview of historical developments of wireless power and an analysis on the use of Teslas resonators in domino forms for wireless power transfer. Relay resonators are spaced between the transmitter coil and the receiver coil with the objectives of maximizing energy efficiency and increasing the overall transmission distance between the power source and the load. Analytical expressions for the optimal load and maximum efficiency at resonance frequency are derived. These equations are verified with practical measurements obtained from both coaxial and non-coaxial domino-resonator systems. To avoid the use of high operating frequency for wireless power transfer in previous related research, the technique presented here can be used at sub-Mega-Hertz operation so as to minimize the power loss in both the power supply and the output stage. We demonstrated both theoretically and practically that unequal-spacing for the coaxial straight domino systems has better efficiency performance than equal-spacing method. Also, the flexibility of using resonators in various domino forms is demonstrated.
ABSTRACT A new design of low-cost and low-profile power transformer is presented in this paper. T... more ABSTRACT A new design of low-cost and low-profile power transformer is presented in this paper. The manufacturing cost of a power transformer can be reduced using the proposed printed-circuit board (PCB) transformer. The transformer windings are etched on the opposite sides of a double-sided PCB. Self-adhesive ferrite polymer composite (FPC) sheets are stuck on the two PCB surfaces to shield the magnetic flux induced from the transformer windings. The PCB transformer does not require manual winding and bobbin. A power converter prototype employing the PCB transformer has been implemented. The technique of choosing the optimum switching frequency of the power converter using PCB transformer is addressed in this paper. The maximum power delivered from the prototype is 94 W. The maximum efficiency of the power converter is 83.5%
IEEE Journal of Emerging and Selected Topics in Power Electronics, Jun 1, 2020
With the electric spring (ES) being practically evaluated by utility companies in power grids, th... more With the electric spring (ES) being practically evaluated by utility companies in power grids, there is a need to explore its practical implementation aspects of general applications. In this paper, we propose three interior angle control principles for the ES. Systematic analysis and comparative study show that these three control principles lead to different smart load (SL) performance. The operating characteristic curves and distinctive features/advantages of the SL using these three control methods are analyzed and explained. A generalized controller structure suitable for the implementations of all these three angle control schemes is presented. It is practically shown that the same controller structure can be programmed to implement these three angle control strategies. This outcome is the first step to realize a programmable ES-based SL for providing multiple functions.
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