This paper presents the general dynamic descriptions of current-fed converters applied in the solar or photovoltaic applications including an impedance-based method to assess the stability of the corresponding interconnected system. Several earlier unknown general parameters are indentified governing either the low-frequency behavior of the closed-loop converter or affecting the source or load interactions. Experimental evidence is provided to support the theoretical findings based on current-fed superbuck and boost converters both in time and frequency domains.

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In this paper, by employing thermal characteristic modeling to the main components of the vehicle model for example, engine, transmission and battery, we examine the heat energy management and fuel consumption of the testing drive patterns especially during warming up process. The simulation data agree well with measurement data. Our vehicle simulation results provide VHDL-AMS validity for multi-domain energy management and the vehicle system planning.

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Single-event burnout (SEB) caused by cosmic ray neutrons leads to catastrophic failures in insulated gate bipolar transistors (IGBTs). It was found experimentally that the incident neutron induced SEB failure rate increases as a function of the applied collector voltage. Moreover, the failure rate increased sharply with an increase in the applied collector voltage when the voltage exceeded a certain threshold value (SEB cutoff voltage).
In this paper, transient device simulation results indicate that impact ionization at the n-drift/n⁺ buffer boundary is a crucially important factor in the turning-on of the parasitic pnp transistor, and eventually latch-up of the parasitic thyristor causes SEB. In addition, the device parameter dependency of the SEB cutoff voltage was analytically derived from the latch-up condition of the parasitic thyristor. As a result, it was confirmed that reducing the current gain of the parasitic transistor, such as by increasing the n-drift region thickness d was effective in increasing the SEB cutoff voltage. Furthermore, `white' neutron-irradiation experiments demonstrated that suppressing the inherent parasitic thyristor action leads to an improvement of the SEB cutoff voltage. It was confirmed that current gain optimization of the parasitic transistor is a crucial factor for establishing highly reliable design against chance failures.

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Advances in the industrial field demand sophisticated electrical motors. However, degradation of traditional ball bearing systems can reduce the efficiency of the motor over time. In addition, bearings require regular maintenance such as lubrication and replacement. Moreover, they cannot be used under some specific environments such as high temperature and vacuum. In order to overcome these problems, this paper proposes a novel active magnetic bearing design. It has only four poles to control the horizontal and vertical suspension, and it is possible to increase the coil winding number without an increase in shaft length. Hence, we can design a high attractive force and stiffness bearing. The stator was initially designed by magnetic field analysis. A simple experimental setup was fabricated in order to confirm the operation principle and attractive force characteristic. The time domain dynamic performance was confirmed by simulation and experimental results. The experimental results verified that the proposed magnetic bearing has sufficient performance for industrial application. Additionally, a small size hydraulic generator was designed for future application.

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In order to reduce power consumption of electronic equipment in stand-by mode, idle-mode and sleep-mode, a simple efficiency improvement technique for switching regulator in light load region is proposed. In this technique, under the light load, the small switching elements in a MOSFET driver circuit are used instead of the switching elements in a main regulator circuit to reduce driving losses. Of course, under the load heavier than light load, the MOSFET driver drives the switching elements in the main regulator circuit. The efficiency of a 2.5V/5A prototype buck converter is improved from 47.1% to 72.7% by using the proposed technique.

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This paper presents stability analysis of a distributed generation (DG) controller⁽¹⁾, in an islanded mode, based on the Mapping Theorem and the Zero Exclusion Condition, and validates the results based on a laboratory scale experimental setup. The DG unit is interfaced to the host system through a voltage-sourced converter (VSC). The control strategy regulates the load voltage at the desired value in the islanded mode, despite uncertainties in the load parameters. The frequency of the island is controlled in an open loop manner by an internal oscillator. The experimental results show that the controller provides robust voltage control for a wide range of load parameters, and even maintains the voltage within the prescribed range during the start-up transients of a motor which is part of the island load.

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Axial-gap self-bearing motor (AGBM) is an electrical combination of an axial flux motor and a thrust magnetic bearing, hence it can support rotation and magnetic levitation without any additional windings. The goal of this paper is utilization of the state observer to research a new capability of sensorless speed control of a salient AGBM. First, analytical and theoretical evaluation for a sensorless speed vector control of a salient AGBM is presented. The approach is based on the estimation of the extended electromotive force (EEMF) through a Luenberger Observer (LO) with help of reference stator voltages, measured stator currents and measured axial displacement. Then, experiment is implemented based on dSpace1104 with two three-phase inverters. The experimental results confirm that the AGBM can simultaneously produce levitation force and rotational torque. Moreover, speed and axial displacement can be independently controlled without speed sensor.

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This paper describes the influence of rotor eccentricity on permanent magnet synchronous motor characteristics by using the finite element method and several experiments. The rotor eccentricity unbalances the magnetic force and thus increases the mechanical loss. Furthermore, a circulating current generated result in an increase of electric power loss in the permanent magnet synchronous motor with three-phase parallel winding of the stator coils. Therefore, we presented that the flux barrier rotor is effective to reduce the harmful effect of the rotor eccentricity.

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Accurate identification of parasitic parameters on a printed circuit board (PCB) and establishment of an effective design method by considering the parasitic components in a power electronics circuit will become major technological issues to increase the power density of power converters. This study focuses on time domain reflectometry (TDR) method in order to identify and to measure the value of parasitic elements on the PCB in which circuit components are closely mounted. A printed circuit board for high power density converter can be effectively designed by using measured value of parasitic parameters. In this paper, two-step measuring method of measuring multiple parasitic inductances of those existing on a buck chopper PCB is proposed. In this method, a discrimination of the location of parasitic elements is identified on the first step, and the values of each parasitic component are measured on the second step. The accuracy of the measured parasitic inductances is verified through the comparison of experimental and simulation results.

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A current control method for the utility interactive inverter based on multi-rate deadbeat control method with FPGA based hardware controller is verified for 100kHz carrier PWM inverter. As the distributed power systems spread, the requirement of the control accuracy for the utility interactive inverter becomes more precise. Deadbeat control is one method to ensure the output voltage or current matches to the references at the sampling instant, so adopting this control law to the utility interactive inverter, the response of the system is much improved with small LC filter component compared with the conventional PI control. A current control method for the utility interactive inverter based on multi-rate deadbeat control, single-rate deadbeat control and PI control were compared. Multi-rate deadbeat control improves the tracking accuracy to the reference compared with the conventional single-rate deadbeat control and PI control. The advantages and disadvantages are discussed through simulations and experiments.

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The permanent magnet synchronous motor offers the possibility of obtaining higher efficiency in a smaller motor size. However, it is difficult to vary the range of high motor efficiency because of its constant magnetomotive force (MMF) level. This paper proposes a variable characteristic motor that embodies a new concept of the compound magnetomotive forces (CMMF) motor. The motor uses a special magnet arrangement that has the MMF of components with different number of pole pairs. The application of compound current control to this motor makes it possible to vary the motor speed and torque (N-T) characteristics. This paper describes the derivation of the theoretical equations for this CMMF motor. It also presents the results of FEA and experiments conducted with the prototype motor to demonstrate the validity of the CMMF concept.

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In a transportation system, a merging control strategy is necessary to avoid collisions between vehicles at a merging section with entry lines. In this study, under the assumption that each entry line is assigned time-independent priority, we analyze traffic congestion with a stochastic model. A quantitative estimation of the congestion is successfully obtained in terms of the average queue length and the average queuing delay. On the basis of analytical results, we propose a control strategy that changes the priority periodically. Using simulation, it is clarified that the proposed control strategy gives an arbitrary values of the queue length and the queuing delay on each line.

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This paper proposes a new torque-sensorless torque control method for permanent-magnet synchronous motors (PMSMs). The proposed method can almost perfectly compensate the 6th harmonic torque ripple that is caused by the nonsinusoidal distributions of the back EMF and rotor magnetic flux of PMSMs. The torque control system is, in principle, constructed on the basis of the vector control, but has two new dedicated speed-varying devices—a harmonic torque observer and current controller. The speed-varying harmonic torque observer can estimate the harmonic component over a wide speed range, even in the case where the produced torque is constant, and generate a suitable compensating signal. The speed-varying current controller shows stable control performance over a wide speed range, it can fully track the compensated current command containing the dc and 6th harmonic components. The effectiveness of the proposed method is examined and verified through extensive numerical experiments.

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In this paper, we propose a new control method of the inverter frequency and the inverter output power with load resonant frequency adjusting phase shift inverter. The proposed control method is applicable to stet the phase-shift inverter with only one output current sensor. When the proposed method is employed, the fundamental waveform signal of inverter output voltage is obtained because the output voltage of a phase-shift inverter is a pulse waveform. Unity power factor and a high efficiency are achieved by adopting the proposed method involving the tracking control of load resonant frequency. In the proposed method, the fundamental waveform signal of inverter output voltage coincides with the detected inverter output current waveform. Moreover, as the inverter output power is regulated by controlling the phase angle of inverter leg in this proposed method, soft-switching control can be realized. In study, the validity of the proposed method is confirmed on the basis of experimental results.

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The method for designing the sensitivity function of a multiple-input single-output servo system is proposed. The method does not require weight or a weight function unlike linear quadratic (LQ) or H_∞ design. First, a controller candidate is derived by taking into consideration the specification of robustness of the plant system. Then, the sensitivity function is derived from the gain specification of the sensitivity function. As the design of a multi-rate controller can be shown to be equivalent to the multiple-input single-output system, the method is employed to design the multi-rate VCM position control system. The multi-rate controller is designed such that at frequencies higher than the Nyquist frequency, the desired robustness is achieved.

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Our research has been served for study on control, operation, analysis of power sy stem, which consists 2 D.C., 3 M.C., and 11 B.C. students. At pr esent development of smart grid flexiblization is mainly focused.

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