Novel Transmitting Power Control Method without Signal Communication for Wireless Power Transfer via Magnetic Resonance Coupling

Wireless power transfer (WPT) via magnetic resonance coupling has been widely studied for vehicle applications, particularly the stationary and dynamic charging of electric vehicles. Our research group previously proposed a wireless in‐wheel motor to improve the reliability and safety of in‐wheel motors. Transmit power control is necessary to achieve stable WPT. We proposed a control method that uses a feedforward controller on the primary side and a feedback controller on the secondary side. However, the control method may cause shortfalls in the transmission power owing to modeling error, coupling coefficient variation, and signal communication delay. In this paper, we propose a novel feedback control method for the primary side based on conversion ratio estimation. The effectiveness of the proposed method was verified by simulations and experiments on the load current control of a constant voltage load and load voltage control of a constant power load.     

Development of –1 MV DC Filter and High‐Voltage DC Measurement Systems for ITER NBI

This paper presents the development results of a ?1 MV dc filter and dc measurement systems for an ITER (International Thermonuclear Experimental Reactor) neutral beam injector (NBI) system. High accuracy of 0.5% and fast responsivity of 3.3 μs, ?3 dB are required for the dc measurement systems: both dc voltage dividers and DCCTs. Circuit design and thermal flow design were carried out to clarify and minimize their effects on the accuracy and responsivity. The validity of the established design was demonstrated by the actual‐product tests; temperature rise of each components fell below the allowable value; inner components of dc filter withstood dc ?1.2 MV; each voltage divider accurately measured the voltage during the dc ?1.2 MV withstand voltage test; the voltage dividers and the DCCTs were adequate to the requirements of responsivity (3.3 μs, ?3 dB).     

Note on the existence regions for eigenvalues of the solution to the discrete Lyapunov matrix equation

Upper and lower bounds for each eigenvalue of the solution to the discrete Lyapunov matrix equation have been reported (Mori et al. 1982 b). A generalization of this result will be presented in this note.     

Vacuum Insulation and Achievement of 980 keV, 185 A/m~2 H-Ion Beam Acceleration at JAEA for the ITER Neutral Beam Injector

Vacuum insulation of 1 MV is a common issue for the HV bushing and the accel- erator for the ITER neutral beam injector (NBI). The HV bushing as an insulating feedthrough has a five-stage structure and each stage consists of double-layered insulators. To sustain 1 MV in vacuum, reduction of electric field at several triple points existing around the double-layered insulators is a critical issue. To reduce electric field simultaneously at these points, three types of stress ring have been developed. In a voltage holding test of a full-scale mockup equipped with these stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, whose target is the acceleration of a H ion beam of 1 MeV, 200 A/m 2 , the gap between the grid support was extended to suppress breakdowns triggered by electric field concentration at the edge and corner of the grid support. This modi- fication improved the voltage holding capability in vacuum, and the MeV accelerator succeeded in sustaining 1 MV stably. Furthermore, it appeared that the H ions beam was deflected and a part of the beam was intercepted at the acceleration grid. This causes high heat load on the grids and breakdowns during beam acceleration. To suppress the direct interception, a new grid was designed with proper aperture displacement based on a three dimensional beam trajectory analysis. As a result, 980 keV, 185 A/m 2 H ion beam acceleration has been demonstrated, which is close to the ITER requirement.     

INFLUENCE OF DESIGN AND OPERATING CONDITIONS ON THE SYSTEM PERFORMANCE OF A TWO-STAGE ADSORPTION CHILLER

This article aims at clarifying the possible design and operating conditions for silica gel-water adsorption refrigeration cycles driven by near-ambient temperature waste heat sources (between 45 and 75°C) with relatively small regenerating temperature lifts (15 to 45 K). A two-stage silica gel-water advanced adsorption chiller is introduced and a simulation model of the chiller was developed to analyze the influence of operating and design conditions on the system performance (coefficient of performance, COP, and cooling capacity). It was hypothesized that the proposed chiller can be driven by low temperature waste heat at 55°C to produce effective cooling. Simulation results show that the operating conditions such as cycle time and hot and cooling water inlet temperature have an influential effect on cooling capacity and COP. COP is proportional to cycle time and heat transfer coefficient as well as inversely proportional to the cooling water inlet temperature, while there are optimum values of hot water temperature and silica gel weight for maximum COP. Cooling capacity mainly improves with the addition of silica gel weight and decreases as cooling water temperature increases. Simulation results also revealed that the system performance can be improved significantly by setting the design and operating conditions optimally.     

Unified Theory of Electromagnetic Induction and Magnetic Resonant Coupling

The difference between electromagnetic induction and magnetic resonant coupling was pointed out in the first proposal of electromagnetic resonant coupling. However, there was no clear technical comparison between the two methods. Therefore, in this study, five circuits are compared by using a phasor diagram, which is a basic and well‐known method in electric circuit theory. The transition from typical electromagnetic induction to magnetic resonant coupling is shown. The mechanism of the high efficiency and high‐power transfer across a large air gap and displacement is discussed, where the primary‐ and secondary‐side resonant frequencies are the same. From the above discussion, we conclude that when the specific conditions of electromagnetic induction are satisfied, the wireless power transfer can be categorized as electromagnetic resonant coupling. The unified theory of electromagnetic induction and magnetic resonant coupling is verified through experiment.     

Further comments on ‘Comments on “On an estimate of the decay rate for stable linear delay systems”’

It is pointed out by a simple counterexample that the theorem derived in the above note is erroneous.     

Convergence property of interval matrices and interval polynomials

In association with robust control-system design and analysis, the Hurwitz property of interval matrices and interval polynomials has recently been actively investigated. However, its discrete counterpart, the convergence property, has seemingly not been much discussed. In this paper, this property is studied in comparison with the Hurwitz counterpart. Some conditions under which interval matrices or interval polynomials are convergent are derived.     

Elucidation of mechanism of aminoreductone formation in the Maillard reaction of lactose

The aim of this study was to elucidate the formation mechanism of aminoreductone, an important indicator for estimating the extent of Maillard reaction of lactose and amino compounds. Using the model system of lactose and butylamine, the model solution of lactose and milk proteins, and milks, it was concluded that d ‐galactose was liberated at the same time as the generation of aminoreductone. It was shown that the extent of the Maillard reaction and the lactose degradation during heating depended closely on the concentration ratio of amino group/lactose in the sample solution.     

Scaling Law of Coupling Coefficient and Coil Size in Wireless Power Transfer Design via Magnetic Coupling

Wireless Power Transfer (WPT), such as magnetic resonant coupling using a magnetic field, is being studied and discussed for a wide variety of applications. When the transmission distances are large, very large transmitters and receivers need to be considered. However, in the early stages of an investigation, it might be prohibitive to manufacture and evaluate coils of such a large size. To reduce costs and effort, a scaling law can be used to estimate the WPT efficiency of very large coils using the results of smaller coils. In this paper, a scaling law is proposed that relates the coil size to the coupling coefficient, assuming the ratio between the coil diameter and coil length remains constant. The coupling coefficient is one of the parameters that determine the maximum efficiency of magnetic field WPT. The proposed method was verified by an electromagnetic field simulator and experiment. The results of this study provide an easy method for estimating the WPT efficiency of very large coils.