In recent years, the number of PHVs has been increasing. DCDC converters using LLC/CLLC are used for automotive electrical components, but in order to improve fuel efficiency, miniaturization, weight reduction, and high efficiency are indispensable issues. One method is a bidirectional isolated DCDC converter. This method is superior to the non-isolated type in terms of EMI and safety because the DC voltage can be freely selected by the transformer and the ground can be separated, and various circuit methods have been studied and proposed for use in quick charging devices for EVs. On the other hand, when a non-isolated or isolated DC/DC converter is used for automotive use, it is necessary to increase the switching frequency in order to reduce the size. In that case, it will cause various failures such as induction failure to the data transmission line of the car radio. In order to solve this problem, this paper proposes a new DAB-type DCDC converter system that does not affect a specific frequency without using a resonant circuit in a configuration with a two-level inverter.

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When multiple PMSMs drive simultaneously, the number of inverters required to obtain stable control when different loads applied to each motor. This causes the size of the system large and heavy. To solve this problem, the authors have proposed a method of driving PMSMs in parallel using a single inverter and current transformers. In this paper, we report on the successful parallel drive using current transformers that operates with less power than the rated power of the PMSM. Also, the positive results obtained on the effect on control when the damping resistor connected to the primary side of the current transformers is changed.

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To accurately evaluate the iron losses of motors driven by PWM inverters, we proposed iron loss estimation method for motor using ring specimen excited by dividing voltage that are generated from motor driven PWM inverter. In order to verify the accuracy of the proposed method, we estimated the iron losses of motors during high-load and field-weakening control.

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This paper shows that in a variable flux linkage IPMSM with a bridge installed in stator slots, a maximum operating speed can be significantly improved compared to methods of adjusting volume of permanent magnets or numbers of windings. And, it is shown that the maximum operating speed can be improved even when a torque at low speed is enlarged by increasing volume of the magnets, its effectiveness of the bridges inside slots is clarified.

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Reluctance motors that use no rare-earth materials have attracted attention as the cost-effective rotating machines. However, improving their performance is crucial for industrial applications. This study proposes a multi-phase reluctance motor in which the number of stator and rotor poles are determined using mathematical rules. The motor employs a doubly salient structure in its geometry and drives in either a synchronous or asynchronous magnetic field with respect to the rotor by switching the current waveforms. Both high efficiency and high output modes will be achieved by leveraging the characteristics of each drive mode.

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Recently, high frequency switching devices such as SiC and GaN have been commercialized, leading to the miniaturization of converters. On the other hand, it is necessary to select magnetic materials for reactors and transformers to support high frequency switching. In addition, Dual Active Bridge DC-DC converters are limited in output power by the reactance between the full bridges. In this paper, core materials and windings are selected to enable the DAB DC-DC converter to operate at 200 kHz. Finally, the validity of the design method is verified through experiments.

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In this research, we proposed the introduction of matrix converters in place of conventional distribution transformers as a measure against voltage fluctuations caused by distributed power supplies. However, matrix converters have high output impedance and are prone to voltage distortion caused by harmonic currents. This paper proposes a control method to suppress voltage distortion in three-phase/single-phase matrix converters. The effectiveness of the proposed control is verified by simulation, assuming the case where nonlinear loads are connected.

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Three-phase capacitor-input diode rectifiers have several advantages, including simple circuit topology, low　high-frequency noise, high reliability, and high environmental durability. However, these rectifiers introduce　undesirable low-order harmonics into the input currents. To address this problem, the authors propose a new topology for a capacitor-input three-phase diode rectifier, which they call the “KOBE rectifier”. This topology meets the harmonic limits specified in “IEC 61000-3-2 (Class A)” for output powers ranging from 0kW to 12kW. In this paper, the authors evaluate the transient responses of the proposed KOBE rectifier and confirm through computer simulations that no overvoltage or overcurrent occurs in any of the passive components.

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Motor drive using an inverter causes problems of corona degradation and electromagnetic noise in the motor because the output waveform of the inverter is a PWM-modulated square wave. To solve these problems, the authors have proposed a drive system for induction motors and wound synchronous motors with an LC filter at the output of the inverter. In this paper, the authors applied the filter to a permanent magnet synchronous motor and obtained good results by simulation.

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The lifespan of a home photovoltaic power generation system can be extended by replacing the smoothing capacitor from an aluminum electrolytic capacitor to an MLCC. However, the capacitance of MLCC is small. Therefore, it is necessary to improve the control of the bidirectional chopper and suppress the output voltage fluctuation. Previous research has proposed a PID control that is excellent at suppressing disturbances. In this study, the stability of the control method of the previous research in the presence of modeling errors is verified through Bode plots, simulations, and experiments.

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To reduce noise in a grid-connected inverter with two-phase modulation, a common mode filter using a ground capacitor and a common mode choke coil is connected to the input and output terminals. Excessive common mode current flowed between the input and output common filters. We proposed a two-phase modulation method that introduces a “gradient” to suppress the sudden change in zerophase voltage, which is the cause of the noise. As a result, the common mode current was reduced.

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