Currently, a “sandwiched structure” is being used for the wireless power transmission system, which is suitable for personal mobility. The sandwiched structure is constructed with two power receiving coils sandwiched between two power transmission coils. This structure stabilizes power transmission, regardless of changes in position of the power receiving and power transmission coils. However, detailed circuit analysis of this structure has not been performed, and analysis considering the mutual inductance of multiple coils is required.

In this study, by clarifying the six mutual inductances of the four coils used in the sandwiching structure and performing circuit analysis, the effects on the efficiency were verified. We also performed experiments to prove that the theoretical analysis was correct.

The purpose of this research is to develop an electromagnetic pump system for electrification of casting applications, and this paper reports the evaluation results of drive characteristics considering the electromagnetic fluid elements or time harmonics that are inverter driven. First, considering the electromagnetic fluid elements, an alternative experiment is proposed using oil mixed with aluminum powder, and the results of the lift speeds driven at variable frequencies by a pure sinusoidal power supply are demonstrated. Then, considering the time harmonics driven by a pulse-width modulation control inverter, another experiment is performed through aluminum pipe lifting. The experimental results for lift speed when the combination of carrier frequency and excitation frequency are changed is reported. These results clarify the effects of the two factors on the lift speed.

An LC series circuit type cell voltage equalizer requires a large capacitance capacitor, e.g., electrolytic capacitors, to transiently store the electric charge of batteries. The lifespans of electrolytic capacitors are shorter than those of other electrical and electronic components. Therefore, the lifespans of equalizers are limited by those of electrolytic capacitors. Thus, determination of capacitor deterioration is essential for the long-term stable operation of equalizers. This study proposed an electrolytic capacitor deterioration detection method for the LC series circuit type cell voltage equalizer. In addition, the usefulness of the proposed method was verified based on theoretical analysis, simulations, and experiments. It was confirmed that the proposed method could be used to determine the deterioration of an equalizer.

This report presents the energy loss evaluation and verification of a Permanent Magnet Synchronous Motor (PMSM) with mechanical winding changeover for electric vehicle traction applications in two standard driving schedules: JC08 and Worldwide Harmonized Light Vehicles Test Cycles (WLTC) modes. We designed a downsized mechanical winding-changeover device with a rated current of a few hundred ampere owing to the multiple contacts and aggregation of movable apparatuses. From the calculated results, the energy loss is observed to be reduced by 6% in the JC08 and 2% in the WLTC modes because of improvement in system efficiency by winding changeover. Actual tests performed on a 5kW PMSM illustrate that the system efficiency improves by up to 5% owing to the reduction of inverter loss and harmonic components of the motor current.

This paper proposes a new method for input current control of power factor correction (PFC) with continuous conduction mode (CCM), which does not require input voltage detection. As a control method that does not use input voltage detection, pulse width modulation (PWM) with the inductor current as the modulated signal is already in practical use however, this approach has limitations for the range of inductance values used. In CCM-PFC, the input rectified voltage and low-frequency component of the voltage of the switching circuit are approximately equal in the stable state as well as proportional to the PWM signal. This study uses the previous modulated signal as the estimated voltage value to generate an instantaneous current command for feedback control. In addition, a method to suppress the influence of the DC voltage ripple by changing the voltage control gain according to the value of the DC voltage was employed. From the evaluation, it was confirmed that the harmonics of the input current were suppressed within the specified range of values.

This paper presents a novel mathematical-model-based simulation method for wound field motors. In the proposed method, motor inductance is represented using an alternative magnetic flux model generated by a radial basis function network. Consequently, computational costs for realizing model-based simulation can be significantly reduced. To validate its effectiveness, the proposed method is applied to two types of wound field motors. Numerical results demonstrated that the model-based simulation method using an alternative flux model is effective for calculating motor characteristics.

Three-phase diode rectifiers have several advantages, such as simple topology, low amounts of high-frequency noise, high reliability, and high environmental durability. However, these rectifiers produce undesirable lower-order harmonics in the input currents. To overcome this problem, a three-phase choke-input-type diode rectifier with AC-side inductors is presented here, which meets to the regulations of JIS C 61000-3-2 (Class A). In this study, the three-phase diode rectifier (3.0kW, 200V/50Hz) is validated through experimental results.

This paper proposes an impedance measurement method in the dq domain for a three-phase power converter system. The proposed method comprises three steps. First, the perturbation of a frequency response analyzer (FRA) is generated as a dq domain signal, which is inversely converted to three-phase signals using a digital signal processor (DSP) and applied to an actual system as series voltage or shunt current excitations. Second, the three-phase current or voltage responses are measured and reconverted to the original dq domain signals using the DSP. Third, the impedance characteristics are obtained using the FRA based on the derived ratios between the excitation and response signals. The proposed method is validated by comparing the analytical and experimental results.

In critical mode power factor correction (PFC), the switching frequency is varied to achieve a sinusoidal input current waveform. Under certain conditions, a higher frequency increases the loss and noise. Meanwhile, the limitation of the switching frequency leads to an increase in input current distortion. This paper proposes a method to prevent an increase in distortion by compensating the pulse width at a limited frequency. Using this control method, critical mode PFC with a limited maximum switching frequency was evaluated. As a result, the total harmonic distortion of the input current was lowr than that before the frequency limitation. Furthermore, the improvement in efficiency and the reduction in conducted EMI were confirmed.

In this paper, a method of switching a circuit in three regions (light load, middle load, and heavy load) by using coupled inductors as auxiliary inductors is proposed. The efficiency of the proposed circuit can be improved by up to approximately 2.8pt while maintaining the ZVS range expansion via simulations. In addition, because the core can be shared by coupling the auxiliary inductors, the circuit size can be smaller than that obtained when two non-coupled inductors are used to vary the auxiliary inductance value.

This paper proposes that wireless time synchronization by GNSS (Global Navigation Satellite System) can be applied to the control of power conversion circuits, and clarifies its validity through experiments. This paper shows that a highly accurate synchronization can be obtained by employing a synchronization system based on GNSS. Moreover, the control signals of each power device in a half-bridge inverter are connected to a controller with GNSS and driven using 10kHz switching, which enables operation of the power conversion circuit without causing a leg short circuit.

The Power Electronic Systems (Hirase) Laboratory in Toyo University has a comprehensive research policy on the broad topic of power electronics and power systems. We are aiming for applications in the areas of sustainable, renewable energy-derived distributed power sources, high-precision data analysis, and earth-friendly mobility for future zero-emissions.