This paper proposes a torque ripple suppression method for a switched reluctance motor (SRM) with only measurable parameters. A large third-order torque ripple is generated via a conventional method with constant dq0-axis current, which is the dq-axis current and zero-phase current converted from the three-phase current of the SRM. The proposed method derives the zero-phase current with the third-order harmonic to suppress the torque ripple from a torque equation by considering the spatial harmonics of the inductance profile up to the fourth order and torque/current ratio in the entire region. Additionally, the average torque equation is derived from the inductance expressing the magnetic co-energy at the magnetic saturation. Consequently, the experimental results confirm that the torque ripple is reduced by 86.5% in the linear region and by 83.2% in the magnetic saturation region compared to the conventional method with the constant dq0-axis current. Finally, the derived average torque equation agrees with the experimental results, including the error of 5.2%.

This paper proposes a coupled-inductor circuit that suppresses cross currents flowing through modular paralleled power converters. The proposed circuit consists of coupled transformers, a current sensor, and amplifiers. The circuit operates as coupling inductors when cross current flows through the converters, such that the volume of the inductors can be considerably minimized. In addition, the circuit can be used as a current sensor. The frequency bandwidth of the sensor can be further improved by adding a few components. The experimental results show characteristics of cross current suppression and current detection, and the propriety and effectiveness of the proposed circuit are confirmed.

A novel high step-up DC-DC converter suitable for the power interface of fuel cells is presented in this paper. The proposed converter features a multi-resonant tank for achieving high-step up ratio under zero current soft switching (ZCS) without any snubber circuits. The simple and minimized-component topology is beneficial for Mega-hertz driving of Gallium Nitride (GaN) power transistors with effective reductions of switching loss, electromagnetic emission interference (EMI) noise, and ripple-free DC input current. Mode-transitional power stages are described in detail, following that the high step-up principle is revealed by means of frequency-domain analysis. The essential performances of the proposed circuit topology are demonstrated by simulation and experiment of 1.8MHz-120W prototype whereby effectiveness of the snubberless and multi-resonant topology are verified from the practical point of view.

This study aims to develop a power supply system without a traction transformer for weight reduction and downsizing. Transformer-less power supply is expected to realize step-down, rectification, isolation, and motor drive using a high voltage silicon carbide (SiC) power device. The primary challenge of this work is developing a novel circuit that isolates the motor drive circuit from the AC line without using the traction transformer. Accordingly, we devised a flying capacitor circuit to solve the existing problems and aims for capacitive isolation. Subsequently, we devise a nesting capacitor as a short-circuit prevention measure. We report the isolated circuit configuration and operating principle.

In recent years, resilience-enhanced building buildings have been attracting increasing attention, in which photovoltaic (PV) power generation and storage batteries are installed in office buildings to continue operations even during a grid outage. PV power generation and storage batteries can be introduced to office buildings to continue commercial operations in the case of grid outages. When introducing PV power generation and storage batteries into a building, the total cost, which is the sum of the equipment installation cost and the damage cost in the event of a disaster, is crucial. When installing PV power generation and storage batteries in a building and calculating the total cost of using these facilities in the event of a disaster, it is necessary to consider the uncertainty of power demand and the amount of power generated by PV power generation. Monte Carlo Simulation is a method to consider uncertainty. However, it has a problem that the combination of conditions becomes enormous, and the calculation load is high when the total cost is calculated. Therefore, in this study, we propose convolution as a method to reduce the computational load generated when calculating the probability distribution of the total cost generated by strengthening the resilience of the building.

This paper proposes all-pass filters (APFs) to enable the reversal operation for the speed sensorless control of induction motors.

Thus far, various speed sensorless control methods that employ voltage and current models have been proposed. However, the accuracy of speed estimation in the low-speed range decreases because of the use of a quasi-integrator for flux estimation. This paper employs APFs to realize highly accurate flux estimation, which is a correction method of position estimation designed for permanent magnet synchronous motors, and indicates that the conventional APF approach fails to realize the reversal operation because it is designed under the condition of positive frequency.

This paper proposes a novel APF structure and its switching strategy for the reversal operation considering negative and positive frequencies. In addition, the effectiveness of the proposed method for the speed sensorless control of induction motors is demonstrated experimentally.

This paper proposes a self-conducting current bypass circuit for series-connected diodes in high power semiconductor light source. This circuit enables the main circuit current flow continuously, even if several of the diodes connected in series are open because of breakdowns. Herein, the composition, operation, and circuit design method of the proposed circuit are described. Moreover, the development of a simulation model of the fuse, which is an element of the circuit, is described. Furthermore, the simulation result of the proposed circuit using the fuse model is presented, and the method of determining the circuit constant based on the simulation result is demonstrated. Finally, by connecting a prototype circuit based on this study in parallel with series-connected diodes, we show that the main circuit current of 60A flow continuously even when one of the diodes is open.

Subsurface magnetic imaging using the electromagnetic field reconstruction is a non-destructive evaluation methods for electric components and circuits. Subsurface magnetic imaging has a considerable limitation because the resolution depends on both the measurement distance and sensitivity of magnetic sensor. In principle, it is difficult to evaluate electronic components and circuits with currents that exceed the response frequency of the sensor. In this study, we propose a down-conversion method for the magnetic field distribution and electric current path images of an isolated DC-DC power conversion circuit, with currents exceeding the response frequency of the magnetic sensor. The circuit was measured with a connected resistance and open circuit condition. The magnetic field distribution and the current path images accurately show that the magnetic field transferred the energy from the input side to the output terminal. Furthermore, the electric current path image shows that there is no electric current flow to the output when the terminal was in open circuit condition.

Boost converters are key components of DC power conversion used for electric mobility and renewable energy applications. In addition to constant voltage control of the output, variable voltage control has been attracting attention in recent years for high-efficiency drive of loads. However, the dynamic characteristics of boost converters exhibit nonlinear and nonminimum phase characteristics. Therefore, the inverse model for feedforward control is unstable, making high-precision voltage trajectory tracking control challenging. This study aims to present a noncausal and nonlinear feedforward controller to compensate for the nonlinear and nonminimum phase characteristics of the boost converter and to achieve perfect tracking control with respect to the output voltage trajectory. This study also establishes a method for identifying circuit parameters and deriving the time length of noncausal control input for practical implementation. The effectiveness of this control method is demonstrated by experiments using a boost converter.