According to the request of utilizing renewable energy resources such as photovoltaic generation systems, more and more inverter-based generators will be installed into a power system. In the circumstances, stabilization of the grid becomes important, especially in a small-scale power system called as a microgrid. The authors have developed a converter control scheme which enhances the synchronizing torque of the grid by adjusting its output voltage phase. In this paper, the effectiveness of the proposed control is verified in various situation in a microgrid model. The results were compared with a similar control that adjusts output power according to frequency. In particular, this paper reveals that the proposed control is more effective when it is equipped to a large number of distributed generators with small capacity. In addition, it is proposed and verified how to enable an intentional islanding the microgrid.

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In recent years, the electrification of aircraft has progressed, and the capacity of electricity is increasing. Electrical accidents can lead to fires in the cockpit and life-threatening accidents such as loss of control and crashes. In addition, as a result of an arc occurring due to a malfunction in the circuit or battery device, the flight may be canceled or an emergency landing may occur. For example, the mainstream of generators used in aircraft is the field winding type because the output is stopped by cutting the field winding in the event of a generator accident. On the other hand, with the increase in capacity, the development of a high-output permanent magnet type synchronous generator with a built-in engine is progressing, and there is an advantage that output can be obtained just by rotating. However, when the dielectric breakdown of the winding occurs, various circuit short circuits occur, and there is a problem that the overcurrent continues and the generator ignites. In order to solve the problem, this paper proposes a short-circuit detection method inside the generator. We also report the usefulness of the short-circuit test using a 20kW system.

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In the present study, the authors discuss the dead-time compensation method for two-phase pulse width modulation (PWM) and experimentally verifies its validity. Present results note that two-phase PWM proves to halve the dead-time error compared with the three-phase PWM. Furthermore, the authors verify that the proposed two-phase PWM published previously has very similar characteristics to the conventional two-phase PWM. Therefore, the present results indicate that the compensation voltage for the dead-time error of two-phase PWM is half of the general compensation method.

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This paper presents a zero phase angle (ZPA) load-independent and -adaptable (LIA) high-order resonant inductive wireless power transfer (IWPT) systems. By designing a ZPA frequency that makes all the mesh networks resonate at the same frequency, constant current (CC) or constant voltage (CV) output mode is achievable for the variations of load variations for voltage / current source. In addition to the frequency-domain analysis, characteristics of the high-order IWPT are investigated by a dual-side LCC resonant tanks, where the load power can be controlled over the wide range by pulse frequency modulation (PFM) / phase shift pulse width modulation (PS-PWM) hybrid controller. The performances of the proposed IWPT system are evaluated by experiment of 5.0kW/ 85 kHz-class prototype, after which the validity of the system design methodology is evaluated from the practical points of view.

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The permanent magnet synchronous motor is a highly efficient motor because the loss such as copper loss and iron loss is about half that of the induction motor. For this reason, it is used in various scenes such as electric vehicles, hybrid vehicles, electric railway vehicles, and industrial machinery. However, since PMSM requires synchronous rotation speed information, a sensor is required, and a separate inverter is required for each motor. The authors have already proposed a new control method in which two units are driven in parallel using one inverter. This method used load angle estimation and V/F control, not vector control. Therefore, there was a problem that the control performance did not improve. In order to solve this problem, this paper aims to replace it with vector control and proposes sensor-less vector control using a new PLL. Since the proposed system is driven in parallel with one inverter, it is characterized by vector control by a coordinate system based on the inverter voltage. In this paper, we first verify the actual machine by driving it alone, and report that we obtained good results.

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This paper presents a very simple equation which shows the relation between the reactive power and output power for maximum transfer efficiency. And those equations are common to various compensating systems. We can know easily necessary kVA of mutual reactors and compensating condensers.

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In recent years, WPT (wireless power transmission) using magnetic resonance phenomenon has attracted attention and its research work has been actively progressed. 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 method which consists of power transmission coil with a resonant tank are proposed and discussed under a designed characteristic impedance of transmission coil.

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Wireless power supply systems using repeater resonators are expected to be a promising technology for supplying power to small-powered IoT devices distributed over a wide area. However, the detuning of the repeater resonator caused by the manufacturing tolerance as well as magnetic interference with the transmitter can reduce the amplitude of the repeater current, which leads to the reduction in the power transfer. To address this problem, an autonomous resonant frequency adjusting circuit was proposed for the repeater resonator. However, this method suffers from limited tuning capability because the adjustable range of the autonomous resonant frequency adjustment circuit is limited under high frequency operating conditions. This paper proposes an improved circuit based on this preceding autonomous resonant frequency adjustment circuit to expand the adjustable range in high-frequency operation.

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This research proposes methods for understanding the immunity performance of switching power supplies with an actual load against electromagnetic compatibility (EMC: EMI + EMS(immunity)) of switching power supplies. In the conventional immunity test of switching power supplies (IEC61000-4-4), since the test with a resistive load, there is no effect on the load, even if noise applied from the AC line is transmitted to the load side. However, since the load is usually an actual load, such as an electronic device (PC and other), malfunctions may occur depending on the magnitude of the noise transmitted to the load side. Therefore, in this study, the output voltage spectrum during the immunity test was measured, and the immunity was evaluated considering the effect on the actual load.

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This paper proposes a simplified equivalent circuit model of magnesium-air batteries focusing on the frequency characteristics from 0.1 Hz to 100 kHz for magnesium-air batteries used as a power source in power converters. The proposed simplified equivalent circuit model has fewer circuit elements than the conventional models, so the identification of each circuit parameter can be calculated from the frequency characteristics without trial-and-error fitting. The frequency characteristics of the magnesium-air batteries were measured using an impedance analyzer IM3590. The circuit parameters of the equivalent circuit model were identified from the measured frequency characteristics, and the voltage-current response characteristics under load fluctuation were simulated by a circuit simulator PSIM using the identified circuit parameters. A comparison of simulation and experimental results shows that the proposed simplified equivalent circuit model reproduces the voltage and current characteristics of the magnesium-air batteries under load fluctuations and its usefulness.

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In this paper, we propose the system of SP-type resonant circuit with the DAB DC-DC converter for the wireless power transfer. We derive a novel non-tight transformer circuit and its equation, which isn't using turn ratio parameters, to design for our proposed system. Using this derived circuit equation and a method of designing to system parameters, we fabricated an experimental apparatus which is SPtype wireless power transfer. We confirmed that our experimental apparatus with a wireless power transfer rated at 1000 VA works. The proposed system can high power by a phase difference of the inverter AC voltage is phased and realize bidirectional power transfer.

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