In recent years, there has been an increasing demand for position sensorless control in PMSM drives, and various methods have been studied. Switching noise is a problem in the low-speed sensorless control method that uses the current slope during PWM. Furthermore, another problem is that the inductance does not appear in a sinusoidal distribution owing to magnetic saturation.

In this paper, we improve the sensorless control method that estimates the position from the current slope during PWM, which is greatly affected by switching. Additionally, we build a multi-layer neural network (NN) that directly estimates the position signals by learning a large amount of current data, and verify the driving results in the low-speed range when the learned NN is incorporated into real-time control.

This paper presents a new configuration for the concentrated windings of permanent magnet motors in order to reduce the torque ripple. There are limited choices for the concentrated windings in conventional permanent magnet motors when selecting the numbers of poles and slots, which results in winding factors for harmonics that cannot be zero and the corresponding torque ripple remains. Unlike conventional concentrated-winding motor, whose teeth are all wound with one coil, the proposed concentrated-winding motor has some teeth with multiple coils wound around. The number of turns for each coil can be optimized to reduce its winding factors for harmonics to nearly zero so that the corresponding torque ripple could be significantly reduced. Prototypes of the conventional and proposed motors were constructed, and the experimental results are compared. Simulation and experimental results confirm the torque reduction effect of the proposed concentrated-winding motor.

Downsizing of motors by achieving a high power density is required to meet the emission regulations of each country. In this study, we developed a permanent magnet synchronous motor (PMSM) with high space factor, which enables the motor to be downsized. This PMSM applies the welding-less rectangular coil to shorten the axial motor length. The developed PMSM was verified by elemental and measurement tests. The test results confirmed that (i) the local heating of the welding-less coil was 4.5K and (ii) the torque and coil temperature of the developed PMSM reached their design values.

This study proposes a novel multi-objective shape optimization method for a claw-pole type alternator. In the proposed method, the magnetic characteristics in the generation mode are represented using a simple mathematical model. Consequently, the pareto front, in which the trade-off relationship of power generation between low-and-high speed conditions is expressed, can be obtained without using magnetic and circuit coupled analysis. To validate the effectiveness, the proposed method is applied to a shape-optimization problem of a claw-pole type alternator. The numerical results indicate that the calculation cost of the proposed optimization is substantially smaller than that of the conventional optimization.

In recent years, permanent magnet synchronous motors (PMSMs) are being widely used in home appliances such as air conditioners and fan motors, vehicles, and railway components. In addition, the application of model predictive control (MPC) to control motors is studied to improve the response of conventional PI controllers. In this study, we derive a responsiveness design method based on predictive horizon in a speed control system that estimates position sensorless control using PMSMs. Furthermore, we combine MPC and position sensorless control by setting the responsiveness of MPC so that there is no interference between current control and position sensorless control.

This paper describes a novel pulse shift method for DC bus current detection at low speeds. It is clear that conventional pulse methods cause a growling sound at low speeds. In conventional methods, the pulse-shifting phase is determined depending on the magnitude relationship of the three-phase voltage command, which contributes to the generation of such a growling sound. The new pulse shift method does not use a voltage command to determine the phase to be pulse-shifted, and the phase is always pulse-shifted. Therefore, it is possible to suppress the generation of a growling sound. In addition, this paper also describes some problems associated with the new pulse shift method and their solutions.

An isolated multicellular ac-ac power electronic transformer (PET) is proposed to achieve a high-power-density and low-voltage industrial control transformer. The multicellular converter topology enables development of an ultrafast high-voltage power converter by utilizing high-frequency low-voltage isolated dc-dc converters. The fast response of the multicellular converter minimizes energy buffers, such as inductors and capacitors, and contributes toward the development of a compact and lightweight PET. A prototype of an AC 100V, 1.35kW multicellular PET was fabricated using nine 1.6MHz, DC 48V unregulated dc-dc converters connected in input-series-output-parallel input-parallel-output-series configuration, and the prototype achieved power densities of 4.50W/cm³ and 4.22W/g. Thus, a volume reduction of 1/14th and weight saving of 1/40th with respect to a commercial frequency transformer was verified.

Currently, induction motors are widely used in many industrial applications owing to their simple construction and high reliability. There has been a gradual increase in the demands for on-line health monitoring and fault detection techniques to avoid unscheduled maintenance and economic losses caused by sudden failures. In this study, we focused on the detections of bearing faults, which are the most frequently occurring faults in electric motors, and we adopted the Hilbert-Huang transformation, which is a recent signal processing technique, to analyze non-linear or non-stationary signals. We prepared several bearing samples with varying degrees of anomalies by heat treatments and built them into the motors. Based on the measurements of the stator current waveform to the motors, we determined the factors related to the degree of anomalies of the bearings, by comparing their loudnesses. Consequently, we confirmed that the components of higher-order (more than 3rd order) intrinsic mode functions have a positive correlation with the degree of anomalies of the bearings.

The single-phase diode rectifier offers several advantages such as a simple topology, low high-frequency noise, high reliability, and high environmental durability. However, diode rectifiers produce undesirable lower-order harmonics in the input current. To overcome this problem, this paper proposes a single-phase voltage-doubler diode rectifier without active switching devices, which meets the IEC 61000-3-2 (Class A) regulation. In this study, the main circuit constants that minimize the total size of the ac-side inductor while satisfying the target specifications of the previously proposed rectifier are obtained by computer simulations. Then, the effectiveness of these optimum constants is demonstrated by a comparison with experimental results using a prototype rectifier (3.6 kW, 230 V/50 Hz).

AC-DC converters that are used to generate DC voltage based on a single-phase AC power supply need to suppress the harmonics of the input current. For this, power factor correction (PFC) converters are generally used in single-phase AC applications, and various studies have been conducted. In previous studies, model predictive control (MPC) has been used to reduce grid current harmonics resulting from high responsiveness however, it was applied only to the current controller. In this paper, we propose a configuration in which MPC is applied to DC voltage control and reactor current control. Furthermore, we propose a compensation method that uses modeling errors to handle variations in the output power of the converters.

Uneven irradiance on curved photovoltaic (PV) panels consisting of multiple substrings connected in series causes a significant energy yield reduction because of mismatched substring characteristics. Switched capacitor converter (SCC)-based differential power processing (DPP) converters utilizing diffusion capacitance of PV cells have been proposed in previous works to prevent the characteristic mismatch issue. However, parasitic inductances of cells and DPP converters hinder charge shuttling among cells, resulting in a reduced energy yield of PV panels. This paper examines the energy yield enhancement of the SCC-DPP converter by adding smoothing capacitors to mitigate the negative influence of parasitic inductances. The relationship between the overall energy yield efficiency and substring structure is also investigated. A dc equivalent circuit of the DPP converter is derived for these examinations. Experimental field tests and simulation using the dc equivalent circuit were performed for the 24-cell PV module under various irradiance conditions. The experimental and simulation results agree well, and both results demonstrate the added smoothing capacitors improved the overall energy yield efficiency by several percentage points. Furthermore, the analytical results suggest the optimal substring structure, which maximizes the annual energy yield, varies depending on season and time.

This paper proposes a method to control the output voltage of an online UPS system based on active power decoupling. The experimental results confirm that the proposed method reduces the DC voltage ripple by 72%. Moreover, this paper proposes a technique to control the output voltage during power failure.

Although an external gate-emitter capacitance (C_GE(ext)) has been proposed to reduce the turn-on loss of insulated-gate bipolar transistors (IGBTs), its effect on the turn-off loss (E_off) has not been investigated in detail. In this study, the effect of C_GE(ext) on E_off in an IGBT was investigated. In the case of a relatively low gate resistance (R_G), C_GE(ext) does not affect E_off; thus, the turn-off behavior is independent of C_GE(ext) and R_G. In contrast, in the case of a relatively high R_G, C_GE(ext) affects E_off. When C_GE(ext) is connected to the input terminal of an IGBT, the dV_CE/dt decreases owing to the increase in the effective gate charge (Q_G) due to the addition of C_GE(ext), thereby increasing the value of E_off.

Our research focuses on the high efficiency wireless power transmission and reliable wireless communication system. The activities thorough women in engineering in IEEJ are also introduced.