An inductive power transfer (IPT) system is sometimes applied to the battery charger of electric vehicles. A DC-DC converter with a diode bridge rectifier (secondary-side converter) is connected to the secondary side of the resonant circuit in order to regulate the current and voltage of a battery. In an IPT system, the secondary-side voltage of the resonant circuit changes significantly depending on the coupling coefficient between the primary coil and the secondary coil. In addition, the voltage changes depending on the load condition. Therefore, a buck-boost converter is suitable for the secondary-side converter because the output voltage range is wider than the other converters, and the IPT system with the buck-boost converter is more efficient than the IPT system with the buck converter. In order to develop a high-efficiency IPT system, a theoretical analysis that considers the characteristics of the IPT system is required. Thus, in this paper, the relationship between the coupling coefficient of the coils and the loss of the secondary-side converter is investigated in order to develop a high-efficiency IPT system with theoretical analysis and experiments that consider the coupling coefficient of the coils. In addition, the circuit parameter selection guideline that makes the secondary-side converter more efficient is shown on the basis of the results of theoretical analysis and experiments. As a result, it was confirmed that the tendency of the characteristics obtained with the experiments is similar as that of theoretical analysis. Thus, it was indicated that theoretical analysis in this paper is useful in analysis of the efficiency and loss of the whole IPT system including secondary-side converter.

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The rated output of a motor is determined based on the value of the load current at which the temperature of the motor's parts reaches the permissive limit. Especially, the temperature of the stator coil is considered in many cases. In this research, in order to attain the higher rated output of a motor, a new thermal cooling structure that decreases the rise in the temperature of the stator coil is proposed. Next, based on the proposed structure, a prototype motor was manufactured and evaluated. The results demonstrated the superior performance of the proposed structure in comparison with the conventional structure. Moreover, the press formed coil which is devised with the purpose of enhancing the desired effect is also explained herein.

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This paper proposes a technique for visually controlling a tendon arm based on simple coordinate transformations between binocular visual space and muscle space through polar spaces. Utilization of polar spaces contributes towards simplification of the transformations because both polar spaces and binocular visual space represent distance and orientation. Moreover, biarticular muscles can be used to convert a transformation into a diagonal matrix. Since a coordinate transformation is divided into multiple simple transformations, multiple feedback controllers can be easily implemented in some coordinate systems. In this paper, a visual feedback with time delay and an actuator feedback are adopted as an external and an internal sensor, respectively. The weights of the two feedback systems are adjusted depending on situations. Simulation results show that the internal sensor feedback and visual feedback are effective for initial quick motion and final positioning, respectively.

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This paper proposes a new dynamic mathematical model and new vector simulator for a permanent-magnet synchronous motor with damper winding (DW-PMSM). The rotor of a DW-PMSM has both a permanent magnet similarly to a pure PMSM and a squirrel-cage similarly to an induction motor. Analyzing the behaviors of a DW-PMSM is difficult because of its complex rotor fields. The proposed dynamic mathematical model and vector simulator make it possible to analyze and understand the complicated behavior of a DW-PMSM. The proposed model has the following completeness and generality. 1) It consists of three consistent basic equations for circuit characteristic, torque generation, and energy transmission. 2) It is established in the general reference frame, where the stator and rotor reference frames are included as special cases. The proposed vector simulator is based on the new model, and has the following attractive features. 1) It successfully realizes clear configurations with physically meaningful vector signals, which are helpful for understanding the motor electromagnetic mechanism. 2) Vector signals utilized as transfer signals between blocks are defined in the general reference frame. Consequently, the vector-signal block diagrams in the frame can be directly and easily reduced to ones in a specific frame such as the stator and rotor frames. 3) It is compact. The usefulness of the simulator was verified through reproduction of the complicated behavior of a DW-PMSM.

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In this paper, a new circuit topology and driving method applied to a multi-port converter are proposed. The converter is connected to a grid, battery, high voltage AC load, and low voltage DC load using a multi-winding transformer. The multi- winding transformer, which consists of five isolated windings and a magnetic core, can reduce the number of converters and transformers. The control method, which can distribute electric power from the grid to the high and low voltage loads, was constructed and verified by experimental results. This electric power system can be applied to many isolated applications in the future.

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This paper presents a novel pattern matching based position sensorless control method for IPMSMs. A target IPMSM for the proposed method is designed such that it has high power and torque density, while also being significantly influenced by magnetic saturation. As previously reported in papers⁽¹⁾⁽²⁾, for IPMSMs, heavy magnetic saturation affects the spatial distribution of phase inductances according to rotor positions. Most position sensorless controls at low speeds typically depend on the assumption that phase inductances have sinusoidal spatial distribution according to rotor positions. Therefore, it is difficult to apply conventional methods to IPMSMs with heavy magnetic saturation.  In the proposed method, rotor position is estimated by pattern matching using feature values, so that the phase inductances have unique and reproducible value according to rotor positions. While template data sets are required for the proposed method, the assumption for sinusoidal phase inductances is not. In this paper, the effect of magnetic saturation for position estimation based on conventional methods is discussed in Section 1 and 2. Then, details of the proposed method are shown in Section 3. In Section 4, results of experiments carried out in steady state and transient state are presented. The effectiveness of the proposed method is verified through the experiments.

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Transmitting efficiency is one of the most important characteristics in dynamic wireless power transfer for electric vehicles. In this paper, a simple and efficient topology for a transmitting system called the DC bus system is introduced. Its simplicity maximizes the potential transmitting efficiency. Moreover, a receiving circuit topology and a maximum efficiency control, which is a method to maximize the transmitting efficiency by controlling the secondary voltage, are proposed. A real-time coupling coefficient estimation method is necessary to calculate the secondary voltage command for the control. A simulation and experimental evaluation of the maximum efficiency control was performed using an experimental setup. The results indicate that it provides a large improvement in efficiency and its implementation in a real dynamic power transfer system for electric vehicles is feasible.

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This paper proposes a new control method for a high-frequency cycloconverter consisting of two half-bridge inverters and a series-resonant circuit. This cycloconverter acts as an ac-to-ac direct power conversion circuit without any dc stage. This circuit does not require a diode bridge rectifier, and thus, can be used to reduce forward voltage drops and power losses in the diodes. A new phase-shift control method is proposed to regulate the capacitor voltage in each half-bridge inverter and to achieve zero-voltage switching. The proposed phase-shift control is theoretically discussed and is also verified by an experimental circuit consisting of super-junction power MOSFETs. As a result, the proposed high-frequency cycloconverter exhibits a good power conversion efficiency as high as 97.7% at the rated power of 1.3kW.

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PMSM (Permanent Magnet Synchronous Motor), position sensorless control method by the motor current detection is the mainstream. However, in order to perform mathematical model calculations for the motor, the deterioration of dynamic characteristics due to model errors becomes an issue. This paper presents a partial sine-wave drive system by the motor electromotive force detection.

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Our research target is the power conversion system for Hybrid Electric Vehicle. The purpose of the miniaturized and high efficiency performance for the power conversion system has been achieved by SiC and GaN power semiconductor devices applications, the new generation inductor and capacitor applications, multi-phase circuit applications and digital control for high frequency switching applications.

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