This paper proposes a stability analysis method for a grid-forming inverter with a droop-control in the sequence domain. The analysis is based on the impedance method. First a system operating point is determined and linearized around the point to calculate output impedance of the inverter. Then output responses of the inverter are analyzed for an excitation small-signal in the frequency domain. The feedback control is processed only in the sequence domain. However, the complex conjugate operation in the droop control is found to transform variables equivalently into the synchronous domain. The frequency analysis is processed in a sequence/synchronous mixed domain. Operation behaviors and critical conditions are investigated and validated analytically and experimentally.

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3-phase converters are often used to connect large-capacity photovoltaic power generation and/or electric　vehicles to　the grid. Normally, dq transformation is used for current control of 3-phase converter. The dq　transformation requires the phase of　the grid voltage, and phase locked loop (PLL) is commonly used. However, the increased computational load of the PLL may cause　a delay in responsiveness. In this paper, we propose the current control method without PLL and the method of controlling negative　sequence component using positive sequence component. The effectiveness of the proposed method against grid faults was　confirmed by experiments.

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Small hydropower Generation can be one of the stable base power source because of its high　availability and high energy. We have developed a cost-effective, highly efficient, low-cost packaged micro　hydropower system for the pipe channels that maximizes the amount of power generated and minimizes　installation space, installation costs, and maintenance costs.

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Normally, when multiple PMSMs are driven, inverters are required for the number of PMSMs, even if they have the same number　of rotations, because information on the rotational position and current of each PMSM is needed. This results in higher costs and larger　installation space. To solve these problems, this paper proposes a new system in which three PMSMs are driven in parallel by a single inverter　as an example of multiple units, and reports good results obtained through simulation.

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This study compares operating characteristics of a wireless power transfer (WPT) system based on a vector control　theory, which is used for motor drive system. In WPT systems, generally, switching signals of a power converter are determined　by voltage and current conditions of the circuit, and thus, the square wave drive is applied. In the proposed system, pulse width　modulation (PWM) technique is used for switching signal generation, and the d- and q-axis current control method is applied.　Simulation results show operating characteristics of the proposed system. High efficiency operation is obtained in higher PWM　carrier frequency.

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Recently, photovoltaic power generation is increasing. However, how to dispose PV modules have become a problem. In this paper, we examine the characteristics of a current amplifier combining LEDs and a Si PV module. In addition, we present experimental results of the current amplifier applied to a shunt regulator.

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In this research, we are developing a new system that can be connected in parallel with a home PV system. This time, the effectiveness of the cooperating system was demonstrated by actual verification. This system must not adversely affect existing systems. Therefore, we set a transition time at the start of power supply from the system and considered supplying a certain amount of power. As a result, power was successfully added. We are also studying the effects of the proposed system on PCS control.

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Switching power supplies are widely used as power supplies for electronic equipment because of their excellent features of high efficiency and compact size. On the other hand, switching of power semiconductor devices generates noise. Conducted EMI noise returned to the input side is regulated in the frequency range of 150 kHz to 30 MHz by international standards such as CE marking, etc. In the high frequency band of 10 MHz to 30 MHz, common mode current flows through stray capacitance between electronic devices and ground. In this study, the effect of stray capacitance on conducted EMI noise from 10MHz to 30MHz was examined. The circuit layout of Y capacitors used as common mode countermeasure components was also studied.

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Voltage-fed inverters have dead-time to protect the short phenomenon of the DC-link voltage. However, the dead-time introduces distortion in the AC-output voltage. To solve this problem, various dead-time error compensation methods have been proposed. In contrast, the authors propose novel method of adding dead-time without dead-time error caused by the dead-time for the voltage-fed inverters. In this paper, the principle and theoretical operation of the proposed method are described in detail, and the theory is confirmed by simulation studies.

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In recent years, wireless power transfer has attracted attention in home appliances and electric vehicles. The SP method is typical for wireless power transfer based on magnetic field resonance coupling. However, because a capacitor is connected in parallel with the secondary inverter, reverse power transfer is not possible. This paper proposes an additional inductor circuit topology for reverse power transfer and present a circuit design method and presents a frequency control scheme based on parity-time symmetry theory.

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Currently, the implementation of safety features in automobiles is being encouraged, and the use of electronic components like ECUs is on the rise. Consequently, there is an amplified need for power conversion circuits such as the drive　power supply to be miniaturized. However, this downsizing results in a higher heat generation density. Therefore, the authors have　focused on immersion cooling, which involves the direct immersion of the circuit in a fluorine-based liquid that acts as an insulator. However, as air or water cooling currently dominates the industrial application field, the parameters required to design for　immersion cooling have yet to be clarified. Thus, this study theoretically calculated and compared the overall heat transfer　coefficient, which indicates a radiator's heat dissipation performance, with actual measurements to confirm its validity.

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In recent years, the magnetic resonance has been attracted to realize the effective WPT (Wireless Power Transmission) system under the condition of long distances power transfers. In this WPT, has many advantages in power transmission efficiency under the conditions of low magnetic coupling coefficient. In this paper, a newly developed power transmission technology which consists of resonant tank connected with both power transmission and receiving coil structure are proposed and discussed various point of view.

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