This paper proposes a circuit topology of a matrix converter with a boost-up chopper at the input side. In the proposed circuit, a V-connection AC chopper is used to achieve the boost-up function. The matrix converter and the V-connection AC chopper can be independently controlled. A virtual indirect method can be applied in this matrix converter. An open-loop control with damping control is employed to control the V-connection AC chopper. A problem encountered in this system is the resonance between the input reactor and the filter capacitor. In order to suppress the resonance, damping control is applied in the chopper. In this paper, the loss distribution and the operation of the proposed circuit are described in detail on the basis of results of simulation and an experiment performed using a 1.4-kW prototype circuit. It is confirmed that the proposed circuit can achieve a maximum efficiency of 95.1%.

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A contactless power transfer system for electric vehicles needs to have a high efficiency, a large air gap, good tolerance to misalignment in the lateral direction and be compact and lightweight. In this paper, a new 1.5kW transformer has been developed using novel H-shaped core which is more efficient, more robust to misalignment and lighter than previous rectangular core to satisfy these criteria, and its characteristics are described. An efficiency of 95% was achieved across 70mm mechanical gap. The modeling of iron-loss in the equivalent circuit is also presented. The calculated efficiency using this model shows good agreement with experimental results.

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We have studied the dynamic avalanche phenomenon in an SOI lateral diode during reverse recovery by using a mixed-mode device simulation. In the study, it has been found that local impact ionization occurs near an anode-side field oxide edge, where a high-density hole current flows and a high electric field appears simultaneously. We propose that a p-type anode extension region (AER) along a trench side wall effectively sweeps out stored carriers beneath an anode p-diffusion layer during reverse recovery, resulting in reduction of the electric field and remarkable suppression of the dynamic avalanche. The AER reduces the total recovery charge and does not cause any increase in the total stored charge under a forward bias operation. This effect is verified experimentally by the fabricated device with AER. Thus, the developed SOI lateral diode is promising as a high-speed and highly rugged free-wheeling diode, which can be integrated into next-generation SOI microinverters.

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Wireless electric power distribution is an attractive means of supplying power to mobile equipment such as mobile phones and electric vehicles. Magnetic field coupling is the most popular method for wireless power distribution. However, this method has certain disadvantages such as power decrease in the case of inexact placement of couplings. Wireless power distribution with capacitive coupling has been proposed to overcome the disadvantages of wireless power distribution with magnetic field coupling. It is, however, difficult to transfer high power owing to the small capacitance of capacitive coupling. The authors propose a new power converter suitable for wireless power distribution with capacitive coupling using a novel one-pulse switching active capacitor (OPSAC) to enhance power transfer. The proposed system improves the power transfer efficiency without LC resonance and is hence robust to parameter change. In this paper, a wireless power distribution system with improved OPSAC (I-OPSAC) is proposed. In the I-OPSAC, the dc voltage source for the inverter is replaced by a capacitor because the OPSAC behaves like a reactive element. The I-OPSAC shows stable operation without any feedback loop including dc capacitor voltage control. In this paper, a control scheme and the detailed operational characteristics are reported, in addition to the simulations and experimental results.

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In this paper evaluates a reduced switch count five-level PWM rectifier in a high frequency power supply system. The rectifier is combined a diode clump type topology with a flying capacitor type topology. Moreover, it uses only four switches per leg in spite of being a five-level converter. This paper describes the features of the proposed circuit topology and the corresponding methods of the high input frequency. Finally, the performance of the input current control of the proposed circuit is confirmed using the experimental setup. In addition, the operation of the proposed circuit at a high frequency of 800Hz is confirmed experimentally.

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This paper presents a novel PWM strategy for single-phase to three-phase matrix converters with a small capacitor that compensates for single-phase instanteneous electric power fluctuation. Output voltage and input current references are derived for obtaining a unity input power factor. In the proposed PWM strategy, the number of commutations in all the three phases during a control period is reduced to four. A design method for the small capacitor is developed on the basis of the control ranges of the output voltage and current. The effectiveness of the proposed PWM strategy is verified by experiments.

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This paper proposes a new high-efficiency grid-connection inverter suitable for the interface with thin-film solar cells, which is composed of two bidirectional buck converters and an H-bridge PWM converter connected in series. The switching frequencies of the first bidirectional buck converters are equal to the grid frequency, while the second one is operated at the twice of the grid frequency. The combination of these two converter synthesizes an ac rectangular voltage pulse train from the dc input power. The H-bridge PWM converter is operated at 20kHz with a low dc capacitor voltage to compensate for the harmonic voltage included in the rectangular voltage pulse train. As a result, the proposed grid-connection inverter makes it possible to reduce both switching loss and common mode voltage. Experimental results obtained by a 1-kW single-phase inverter demonstrate a high efficiency of 98% without any common mode voltage.

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The authors investigated the control of welding current with a frequency-controlled inverter power supply. Welding current control requires precision sensing of the inverter current, which can reach 10kA. The current transformers and Hall effect devices commonly used in the industry do not deliver the desired performance. The authors investigated the use of a shunt-type current sensor based on the simplest RI drop method for current detection. This paper discusses the investigation of the extent to which sensor inductance can be cancelled out when using the shunt-type current sensor. Experimental results indicate that the inductance component can be cancelled out, thus making non-inductive operation possible. A current sensor has been prototyped and used in a frequency-controlled inverter power supply, demonstrating that welding current control is possible.

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In this paper, a novel position sensorless control method for interior permanent magnet synchronous motors (IPMSMs) that is based on a novel flux model suitable for maximum torque control has been proposed. Maximum torque per ampere (MTPA) control is often utilized for driving IPMSMs with the maximum efficiency. In order to implement this control, generally, the parameters are required to be accurate. However, the inductance varies dramatically because of magnetic saturation, which has been one of the most important problems in recent years. Therefore, the conventional MTPA control method fails to achieve maximum efficiency for IPMSMs because of parameter mismatches. In this paper, first, a novel flux model has been proposed for realizing the position sensorless control of IPMSMs, which is insensitive to L_q. In addition, in this paper, it has been shown that the proposed flux model can approximately estimate the maximum torque control (MTC) frame, which as a new coordinate aligned with the current vector for MTPA control. Next, in this paper, a precise estimation method for the MTC frame has been proposed. By this method, highly accurate maximum torque control can be achieved. A decoupling control algorithm based on the proposed model has also been addressed in this paper. Finally, some experimental results demonstrate the feasibility and effectiveness of the proposed method.

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This paper describes a proposal of a new magnetic fluid analysis method to calculate the coupling problem of electromagnetic field and flow field with free surface using two-dimensional finite element method. First, it introduces a formulation of electromagnetic and flow field. In order to solve a flow field problem, level set method is employed. Second, experimental verification is shown through the comparison of calculated and experimental results when moving magnetic field is applied. The measured displacement qualitatively well agreed with the calculated. Finally validity of the analysis method is discussed.

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This paper introduces a method for torque ripple suppression control involving the use of the periodic disturbance observer. By using the Fourier transform (or rotating coordinate transform and a low-pass filter), the torque ripple component, which is synchronized with the motor rotation, can easily be obtained owing to its periodic variations. With the new control method, a suppression control system synchronized with the torque ripple frequency can be built. Further, by using the system identification technique, the model system from compensating current value to torque detection value can be expressed as a speed-adjustable one-dimension complex vector in rotating coordinates. This method is suitable for an adjustable-speed drive, and the control parameters and reference model can be adjusted automatically. The most important feature of this method is its excellent performance for mechanical resonance suppression caused by torque ripple. This paper presents analysis and experimental results that validate the method.

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This paper presents a thermal analysis technique for printed wiring boards using an admittance matrix. The proposed technique uses the similarly between electricity and heat, and can be applied to the modified nodal method that is generally used for electrical circuits. This technique can forecast the amount of temperature rise in a printed wiring board with high accuracy, regardless of the anisotropic thermal conductivity and the number of meshes in the finite element method. In this paper, we introduce a method for constructing an admittance matrix for a thermal analysis, and present the results of applying the analysis technique to the printed wiring board.

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A method for reducing motor torque in proportion to wheel slip is applied to an inverter-driven electric locomotive. The motor torque at wheel-slip speed is less than the torque at the maximum tangential force or the adhesion force. A novel anti-slip control method for seeking the maximum value of the tangential force between the wheel and rail is proposed in this paper. The characteristics of the proposed method are analyzed theoretically to design the torque reduction ratio and the rate of change of the pattern between the wheel-slip speed and motor current. In addition, experimental tests are also carried out to verify that the use of the proposed method increases the traction force of an electric locomotive driven by induction motors and inverters. The experimental test results obtained by using the proposed control method are compared with the experimental results obtained by using a conventional control method. The averaged operational current when using the proposed control method is 10% more than that when using the conventional control method.

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This paper proposes a new dynamic mathematical model of permanent-magnet synchronous motors (PMSMs) with magnetic cross-coupling and presents a new analysis of the torque characteristics of the motors. Generally speaking, dynamic mathematical models used for the design and analysis of PMSM control systems must consist of three basic equations that describe the main motor characteristics as an electrical circuit, torque generator, and electromechanical energy converter. In order to obtain reasonably compact models, some characteristics have to be approximated. However, in the case where the approximations used in the three basic equations are different from each other, the dynamic mathematical model often loses self-consistency and becomes self-contradictory. The proposed model, which takes the magnetic cross-coupling into account, is self-consistent and compact, and its effectiveness is validated by experimental data. Using the self-consistency and compactness, this study presents a new analysis of the torque characteristics of PMSMs, focusing on efficient torque generation.

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In recent years, the boost converter system with compact and light weight performance have been required in the Hybrid Electric Vehicle and Electric Vehicle applications. To obtain the miniaturization performance for the passive circuit component, such as the inductor and the smoothing capacitor, the multi-phase method boost chopper circuit with the coupled inductor have been proposed and discussed. In this paper, the optimum control design technique of the multi-phase method boost chopper circuit with the coupled inductor is proposed.

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This paper presents a simple theoretical equation of maximum efficiency for contactless power transfer systems. Conventional theoretical equations are composed of many factors such as transformer's resistances and inductances. The proposed equation is composed only of coupling factor k and Q factors. This shows ideas to improve efficiency of contactless power transfer systems.

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This paper presents an analysis about observer gains of identity dimensional state observers for PMSM sensorless drives. It derives a new relation between two observer gains of minimum and identity dimensional state observers, which gives a design guideline of observer gains of the identity ones.

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Application of resonant snubber switch cell to a single-phase buck rectifier is studied. The resonant snubber switch cell consists of an only active power switching device and a LC resonant circuit. The active power switching device is then turned on and off under the soft switching conditions. The experimental results under the sinusoidal pulse-width modulation (PWM) confirm that the input current can nearly be wave-shaped sinusoidally with a near-unity power factor.

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When train operation are disturbed due to some accidents, passengers have to gather relevant information in order to decide which train they should to take. This paper describes the result of an evaluation test to grasp passengers' train choice behavior when they obtain the information about the situation of individual trains, such as estimated arrival time, congestion rate of each train. It shows that passengers' decision make and behavior for train choice vary depending on the presence or absence of the information, and it is effective to provide detailed information for appropriate train choice.

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