This paper proposed a novel rotor structure for V-shaped interior permanent magnet motors (IPM motors) to reduce the magnet volume. Although the magnet volume, required to obtain the desired torque, could be reduced using a V-shaped magnet arrangement, its effectiveness was limited due to the leakage flux pathing through the central bridge. In the proposed motor, the central bridge was replaced by a nonmagnetic wedge, and the leakage flux path was completely eliminated. For this reason, the magnet reduction effect of the concentrated flux structure in the V-shaped IPM could be maximized, and the magnet volume could be reduced compared with that of conventional motors. To validate its effectiveness, numerical and experimental verifications were conducted. Moreover, the obtained results were compared with those of conventional motors.

In 2-phase HB-type stepping motors, since the phase A and B induced voltages contain 3rd and 5th order components, the dq-axis induced voltage contains 4th-order component. Therefore, the dq-axis magnetic flux includes a 4th-order component, and the output torque also includes a 4th-order component. To suppress this torque ripple, conventional methods include ripple suppression using position and acceleration sensors and manual adjustment of the q-axis current commands. However, these methods increase cost, reliability, and labor. Therefore, this paper reports a new method of torque ripple suppression using position and acceleration sensorless control by improving the current response using a resonant controller and generating q-axis current command values using an artificial neural network (ANN), which is a type of AI model. In this paper, we also confirm the effectiveness of suppressing torque ripple in the mid-to high-speed range through actual machine verifications.

In many power converters, a compensated voltage reference for dead-time distortion is typically preset during the design stage. However, this reference may deviate from the optimal value when semiconductor devices are replaced or when device characteristics change due to operating conditions. As a result, there is a growing need for active adjustment of the compensated reference. This paper evaluates the effectiveness of machine learning techniques for this task, and compares three approaches: (i) an image classification model, (ii) a waveform feature-based linear regression model, and (iii) a one-dimensional CNN regression model using time-series data. Results show that method (iii) outperforms the others.

This paper presents a fast steady-state analysis method for squirrel-cage induction motors (IMs) based on the time-periodic explicit-error-correction (TP-EEC) method. To reduce the high computational cost associated with conventional time-stepping steady-state analysis of cage IMs, the proposed method extends the dq-TP-EEC framework, originally formulated for three-phase electric machines in a rotational reference frame, to polyphase IMs by incorporating rotor slip frequency. The effectiveness of the proposed method is demonstrated through steady-state analysis of two IM configurations featuring closed and semi-closed rotor slots. Numerical results confirm the method's accuracy and reveal that using smaller time intervals significantly improves convergence in transient analysis when the slip is moderate. Furthermore, this study investigates the method's limitations under conditions of low slip frequency, where a large time constant can affect performance.

This paper introduces novel magnetic slot wedges made of a newly developed resin-free magnetic composite material. The novel magnetic slot wedges exhibit superior permeability and strength compared with conventional magnetic slot wedges made of iron powder and resin. Finite Element Method (FEM) analysis indicated that the efficiency improvement of a 7.5kW 2-pole induction motor with the novel magnetic slot wedges was expected to be approximately 1.5 times higher compared to that with the conventional magnetic wedges. Installing those magnetic slot wedges into the originally vacant slot openings of commercially available 7.5kW 2-pole, 7.5kW 4-pole, and 0.75kW 6-pole induction motors resulted in efficiency improvements of 1.6%, 1.1%, and 2.8%, respectively, at each rated output. Noticeable decreased in temperature rise were also observed. Consequently, the novel magnetic slot wedges proved to be effective in improving the efficiency of induction motors without requiring significant design changes, such as increasing the motor size.

To realize a decarbonized world, high efficiency in industrial electric motors, including large-sized motors in the range of several hundred kW, is required. Permanent magnet motors are the most efficient for this purpose. However, their adoption in large-sized motors can be challenging owing to the scarcity and cost of rare earth materials. Owing to this, synchronous reluctance motors (SynRMs) are gaining attention. They do not use permanent magnets in the rotor and are more efficient than the widely used induction motors. However, to determine the operating characteristics of SynRMs, an actual load test is necessary. For large-sized SynRMs over in the range of several hundred kW, conducting this test is expected to be challenging owing to the requirement of large test facilities. This paper proposes a method to examine the operating characteristics of SynRMs using a standalone test and reports the evaluation results of the proposed testing method. This method provides a practical solution for evaluating the performance of large-sized SynRMs, potentially facilitating their wide adoption in industrial applications.

This paper presents a coupled analysis method for vibration energy harvesters based on predictor-corrector approach. To consider the coupling of vibration and electromagnetic systems, time-evolutions of system states are predicted, and coupling factors are evaluated from the predicted states. Then, the next system states are evaluated by solving the system's governing equations. The coupling factors are corrected using the predicted and computed states. It is shown that the proposed method can evaluate the performance of a vibration energy harvester with little computational burden, while the analysis results almost equal those of the conventional quasi-strong coupled analysis method. Moreover, the measurement results show that the proposed method can qualitatively simulate the behaviors of nonlinear vibration energy harvesters.

The use of the reinforcement learning algorithm DQN (Deep Q-Network) can increase the design variables and offers the advantage of enabling more versatile motor optimization design. This paper evaluates the potential and advantages of reinforcement learning-based motor optimization design, which is still in its early stages globally. To demonstrate the performance of the proposed method, the geometry and drive conditions for reducing torque ripple of a FWSM (Field-Wound Synchronous Motor) using DQN were optimized. The proposed method exhibited excellent optimization performance, and it is expected that a more versatile optimization model can be developed by increasing the number of analysis cases.

A vibration suppression method is proposed for a compressor motor driven in the sensorless 120- degree conduction mode. The proposed method estimates motor speed and angle from the zero-crossing points of the back electromotive force (EMF) and suppresses vibration using a disturbance observer in conjunction with a Smith compensator. The experimental results demonstrate that the proposed method reduces the fundamental frequency component of vibration by 94.2% at a low speed of 900min^-1 (0.19p.u.).

Electric vehicles (EVs) and electric aircraft require motors with high power density and efficiency. This study proposes a doubly fed machine (DFM) featuring an air-gap winding (AGW) that operates under magnetic resonance coupling (MRC) to enhance power density and efficiency. The fundamental characteristics of the doubly fed magnetic resonance coupling machine (DF-MRCM) with AGW were analyzed revealing that its high output power results from an increased product of primary and secondary currents without magnetic saturation in the stator and rotor. The machine achieves high efficiency at elevated rotational speeds, attributed to reduced iron losses from MRC and a lightweight rotor constructed from high-strength carbon fiber-reinforced plastic. These design features enable the DF-MRCM with AGW to achieve a high power density of 9.7kW/kg at a high rotational speed of 39,960rpm, making it well-suited for EV and electric aircraft applications.

This paper attempts to separate the AC copper loss, which is significant in high-speed electric motors, into four elements: the skin effect, the in-slot proximity effect, the inter-slot proximity effect, and the effect from permanent magnets. It is found that 84.6% of the AC copper loss in the interior permanent magnet synchronous motor (IPMSM) investigated in this study is caused by the in-slot proximity effect. Furthermore, several countermeasures are presented to reduce the in-slot and inter-slot proximity effects, such as multiple slots, employing finely divided coils, and using aluminum coils. The results demonstrate that the reduction rates of the overall copper losses are 9.0%, 50.1%, and 23.6%, respectively. Furthermore, by combining the three countermeasures, copper loss is finally reduced by 62.5%.

This study shows the design and implementation of an adaptive one sample ahead preview (AOSAP) control structure tailored for non-sinusoidal permanent magnet synchronous motors (PMSMs), implemented in both d and q coordinates. The control strategy employs a first-order reference model and is systematically compared against conventional Proportional-Integral (PI) controllers. The simulation results in Matlab and the experimental evaluations conducted on a Typhoon hardware-in-the-loop (HIL) 604 platform and a physical prototype demonstrate the superior performance of the proposed AOSAP controller. It exhibits lower tracking errors and faster regulation compared to classical PI controllers. The control algorithms are developed on Texas Instruments Delfino C2000 microcontrollers, showcasing the feasibility of the proposed approach in real world applications.

The nonlinear friction force is the predominant force disturbance in a permanent-magnet linear synchronous motor (PMLSM) with guide rails and it can affect position control precision, especially during motion reversals (velocity zero-crossing). To minimize the effect of nonlinear friction on position accuracy in the reciprocating motion of a PMLSM, a compensation scheme consists of an iterative learning-based bang-bang compensator (ILBBC) and a generalized proportional-integral observer (GPIO) is presented in this paper. The ILBBC is utilized to compensate for the abrupt change in Coulomb friction force in velocity zero crossing, and the GPIO is added to enhance the compensation performance for the vicious friction force. To effectively merge the ILBBC and GPIO, a three-stage compensation scheme is proposed; thus, the combination of the ILBBC and GPIO is capable of compensating for nonlinear friction in both velocity zero-crossing and non-zero regions. The design and stability of ILBBC and GPIO are theoretically analyzed. Finally, comparative experiments, which include no compensation, GPIO-based compensation, and ILBBC + GPIO compensation, are implemented under two types of sinusoidal position trajectories to demonstrate the effectiveness of the proposed compensation scheme.

In industrial applications that require low-cost positioning and high torque, stator permanent magnet hybrid stepper motors (SPMHSMs) possess significant application potential. The torque of the SPMHSM is related to the number of teeth per stator pole. However, few studies have analyzed the effect of the number of stator teeth on motor performance. To this end, in this study, we designed SPMHSMs with four, five and six-tooth configurations. First, the topology of the SPMHSM is introduced and its operating principle is analyzed. Next, the three motors are designed with the same PM and electrical load. Lastly, we analyzed the electromagnetic performance of these three motors in terms of several factors including magnetic flux distribution, back electromotive force, detent torque, and output torque. The obtained results show that the output torque of the SPMHSMs with five and six-tooth configurations is 2.61% and 3.26% higher than that of the SPMHSM with four-tooth configuration, whereas that with a four-tooth configuration has a wilder torque-current range.

Current source inverters (CSIs) offer advantages over voltage source inverters (VSIs) in drive systems, particularly for motor windings. CSIs feature integrated output capacitors that provide smooth voltages, mitigating issues such as interturn overvoltages, insulation degradation, bearing currents, and electromagnetic interference. Recent advancements in monolithic bidirectional switches have further enhanced their appeal. However, the complexity of CSI modulation and control limits their adoption compared to VSIs, as engineers are more familiar with PWM techniques for VSIs. To address this, we propose the Equivalent DC Machine (E-DCM) concept, wherein the CSI operates in an open loop with a fixed modulation index, allowing direct torque control of the PMSM through the DC link current. This enables the CSI-supplied PMSM to emulate the behavior of a traditional DC machine, simplifying control while avoiding commutation and maintenance issues. The E-DCM concept is validated through transient time-domain simulations, demonstrating its DC machine-like speed-torque characteristics and effective speed control during acceleration from zero to nominal speed.

Recently, the power density of power converters has increased to minimize their size and weight. However, this increase in power density also leads to higher heat generation density and maximum temperature of converters. Therefore, conventional cooling methods, such as air cooling and indirect water cooling, may not be sufficient to cool high-power density power converters. Liquid immersion cooling has been considered as an effective solution for cooling data center servers. This study aimed to design a high-power density three-phase inverter using a liquid immersion cooling system. The cooling system used hydrofluoroether (HFE) as a refrigerant. The inverter was designed with a 3D circuit structure to maximize superior cooling and dielectric strength of HFE, achieving a power density of 245kVA/L. The cooling performance of the system was verified via computational fluid dynamics (CFD) thermal analysis. The simulation results indicated that the maximum temperature reached 65. 4°C, which is well below the rated value of the switching devices. Furthermore, in experimental heat generation tests with actual equipment, the maximum temperature reached 46.2°C, which was also well below the rated value of the switching devices.

In this study, the loss of a permanent magnet synchronous motor (PMSM) with a ductile iron frame is evaluated. First, the magnetic and electrical properties of the ductile iron FCD400 that was used for the frame were measured. Subsequently, the measured properties were applied to the loss analysis of the PMSM with the ductile iron frame. The results of the analysis demonstrate that significantly large losses are generated in the frame when the stator core is highly saturated. In addition, the effect of carrier harmonics on the generated frame loss was examined. As a result, the frame loss is mainly generated by the fundamental component included in the pulse-width modulation voltage waveform, and the contribution of the carrier harmonics is negligibly small. Finally, the effect of the presence of the frame on the torque performance at low-speed and high-torque conditions is discussed.

This paper presents the design and analysis of cross-pole-shape flux reversal (FR) motors for compact electric vehicles (EVs). First, the optimal cross-pole width is investigated that 2.0° provides high torque, reduces eddy current losses in the magnets, and suppresses even-order harmonics in the no-load induced voltage. An 18/24-pole FR motor is then optimized using a genetic algorithm (GA). The results reveal that the optimized FR motor generates both reluctance and magnet torque due to its cross-pole-shaped stator structure, leading to enhanced torque performance and a maximum torque of approximately 61N·m. The performance of the optimized FR motor is compared to previously reported in-wheel switched reluctance (SR) motor. The FR motor produces higher torque across the entire operating range and maintains an efficiency above 90% over a wide region. Finally, driving performance is evaluated by applying the FR motor as an in-wheel motor in a compact EV. The results demonstrate excellent hill-climbing ability and a maximum speed of 55km/h, which is 10km/h faster than EV with SR motor-based EV.

The creation of negative energy is key to the development of new space propulsion technologies. It has been believed that it is impossible to generate negative energy using electromagnetic methods. However, we have theoretically demonstrated the existence of a mutual induction circuit that can transiently separate zero energy into positive and negative energy. First, a current is passed through one coil of a mutual induction circuit. Next, the power supply switch is turned off and another switch is turned on to connect the two coils in series. Then, a differential connection is immediately established with another coil to form a closed circuit. At this time, the current increase phenomenon and energy separation phenomenon transiently occur due to the rapid cancellation of the magnetic flux. In the proposed circuit, the amount of positive and negative energy that is transiently separated is equal. Therefore, the law of conservation of energy holds. In this study, we carried out a theoretical analysis to maximize the energy separation efficiency of the proposed circuit and clarified the circuit conditions under which the maximum net efficiency reaches 367%, for example, when the coupling coefficient is 0.992. In addition, we conducted experiments to verify the effectiveness of the theory and simulation. The theoretical and experimental values were in good agreement.

Many components in the power grid are developing towards miniaturization. To control the volume and weight of transformers, their working frequency is constantly improving. The influence of high frequency on the distributed parameters of transformers has increased significantly, resulting in voltage distortion, harmonics, and other power quality problems that complicate the internal electromagnetic energy storage. This article analyzes the connection relationship between the topology of stray capacitance parameters and the topology of transformer inductance. Furthermore, a transient model construction method for high frequency transformers under the influence of distorted voltage and harmonics is proposed. The proposed method can describe the response characteristics of transformers under complex operating conditions, such as transient inrush current and the distortion rate of new energy grid connected voltage. The proposed model is suitable for simulation analysis of new hybrid systems.

Magnetic gears, which can transmit power without mechanical contact, offer lower vibration and acoustic noise compared with conventional mechanical gears. A flux-modulated-type magnetic gear stands out due to its high efficiency and torque density because all the permanent magnets consistently contribute to power transmission. This paper discusses the torque-to-weight ratio improvement and permanent magnet usage reduction of large-scale flux-modulated-type magnetic gears, aiming to construct highly reliable, lightweight, and resource-saving offshore wind power generation systems with magnetic gears. First, to demonstrate the effect of the Halbach array on the torque, an air gap flux density waveform in a prototype magnetic gear with Halbach array magnets is directly measured and compared with that using conventional parallel array magnets. Next, by applying the ideas of the Halbach array and multi-polarization into large-scale magnetic gears, improvements in the torque-to-weight ratio and reductions in permanent magnet usage are demonstrated using the finite element method (FEM).

The occurrence of open-phase faults in five-phase permanent magnet synchronous motors (5Ph-PMSMs) disrupts the current balance among the remaining healthy phases, resulting in the introduction of second and fourth harmonics into the position estimation. To address this challenge, this paper proposes an innovative sensorless control approach specifically for open-phase 5Ph-PMSM systems. This methodology integrates improved second-order generalized integrators (ISOGIs) to effectively mitigate undesirable harmonics and extract the positive sequence component from the distorted back electromotive force (back-EMF). Additionally, an adaptive neutral-voltage compensator is implemented to alleviate the asymmetry present in the back-EMF, thereby further enhancing the precision of the sensorless control. The effectiveness of the proposed methodology is corroborated through rigorous experimental results.

This article proposes an indirect vector control for induction motor control in electric vehicle propulsion systems. Torque ripple suppression and improvement of the transient torque response are the key challenges. Therefore, the predictive controller was applied to the current control loop of an indirect vector control. To achieve fast transient response and small torque ripple, this study focused on the performance of the current control loop. A mathematical model of the electric vehicle propulsion system consisting of the mechanic of the electric vehicle load, battery, inverter, and three-phase induction motor is proposed. The accuracy of the model was validated and confirmed using the MATLAB/Simulink program. The hardware-in-the-loop technique was implemented to confirm the fast and accurate current performance for the electric vehicle system. The testing results demonstrated that an indirect vector control based on the predictive controller provided a faster transient current response and less current ripple than the PI controller. As a result, a good transient torque response and small torque ripple were achieved by the predictive controller under changing speed conditions.

Three-phase inverters undergo degradation owing to imbalances in the losses among their components. We have been working to mitigate such imbalances by switching patterns. To this end, we herein propose a variable switching pause period two-phase pulse width modulation (PWM)-based scheme to equalize switching device losses in unbalanced three-phase inverters, thereby enhancing their lifespan. However, usage of two-phase PWM schemes in three-phase inverters may give rise to current harmonics. To overcome this issue, we integrate a pulse-voltage-injection two-phase PWM scheme featuring a variable switching pause period. The experimental results demonstrate that the proposed PWM scheme simultaneously equalizes the switching device losses and reduces the output current harmonics of an unbalanced three-phase inverter operating with an inductive load and induction motor.

This study presents a novel approach for speed control of a separately excited DC motor (SEDC), focused on controlling the field current. Typically, the parameter values and mathematical model of motors are key aspects to consider in the design of controllers, and the process of determining motor parameters is complex. However, designing the control system of fuzzy logic controllers (FLCs) does not require detailed parameters or mathematical models of the motor. Instead, this process relies on the expertise and experience of the designer. In this context, this study introduces an approach for designing the FLC for field current control in SEDC motor speed regulation, which can be applied to other SEDC motors irrespective of the designer's experience and expertise. The experimental results obtained upon comparing the proposed control approach between an FLC and PI controller show that better control closer to the reference speed is achieved in the FLC in both the transient and steady states. Furthermore, the proposed approach can be applied to SEDC motors with varying ratings.

Synchronous reluctance machines (SynRMs) can realize high efficiency without permanent magnets, and recently their application has expanded to larger machines. Our group also developed a 400kW-8488N·m SynRM that achieved a world-class continuous rated torque. For such a large torque and high output machine, indirect measurements based on the superposition principle and equivalent load method are preferred in determining the temperature rise. This is beneficial from the viewpoint of reducing the burden on test equipment, but the method is not authorized for SynRM. This paper applied the conventional method to SynRM in experiments and compared its results with the actual load test to assess its applicability. Consequently, it was clarified that the conventional method, consisting of a no-load and a mixed-frequency equivalent load test, overestimates the temperature rise by 25K or more. Detailed magnetic field analysis revealed that damping loss occurred during the equivalent load test, and its heating affected the temperature rise determination. Finally, we proposed a new method for estimating the temperature rise from the two equivalent load tests performed under the different stator current conditions. It was demonstrated that the method effectively eliminated the damping loss effect and determined the temperature rise with a slight error of 4K.

A reference stator flux linkage calculation method is proposed for realizing maximum efficiency operation in direct torque controlled permanent magnet synchronous motor (PMSM) drives. A key feature of the proposed method is the ability to directly and successively search the optimal input power using a local search algorithm. Thus, the proposed method exhibits less dependency on the parameters of the PMSM compared to conventional parameter-based reference flux calculation method. Specially, the equivalent iron-loss resistance which is difficult to measure is not required. Simulation and experimental results validate the proposed method.

For dual three-phase permanent magnet motors with yokeless and segmented armature (YASA) topology used for electric aircraft propulsion, reliability is a fundamental requirement. Two fault-tolerant control strategies under single-phase open-circuit faults were analyzed in this study: one based on constant magnetomotive force (MMF) and another based on a reduced-order decoupling mathematical model. Minimization of copper loss and maximization of output torque were set as control objectives. Simulation results demonstrate that the motor speed and torque can be maintained at pre-fault levels through fault-tolerant control. However, the connection of the neutral line introduces significant odd harmonics in the current, causing notable torque ripple. Under the constant MMF-based strategy, torque ripple reached 34.35% and 34.38% for the two control objectives when operating at a 50Nm load. In contrast, the reduced-order decoupling model-based control strategy alleviated this issue by mathematical correction of the post-fault model of the dual three-phase YASA machine, reducing torque ripple the range of 18.45%-28.00%.

Induction motor drive systems without rotation speed sensors are already being used in many products. In recent years, the efficiency of induction motors has increased, with the secondary time constant tending to become longer. This paper investigates a new restart method that enables a short startup time for such high-efficiency induction motors. The validity of the new method was verified by experiments using a high-efficiency induction motor.

Permanent magnet synchronous motors are characterized by their compact form factor and high efficiency. They are increasingly being designed as high-speed, multi-pole motors in response to the demand for higher power density. However, with increasing speed and number of poles, the drive frequency of motors increases, escalating the iron losses. These increased iron losses lead to current detection errors, which may cause a decrease in efficiency.

Considering the influence of current detection errors due to iron loss, this paper proposes a new method that uses minor sampling to perform three-shunt current detection. In addition, to improve the detection accuracy of the proposed approach, we designed a method to suppress the detection error. Experiment results show that the proposed method worked stably even with an RC filter inserted, and the effectiveness of the proposed method was confirmed experimentally.

With the increasing use of electric motors as the primary propulsion system in vehicles, vibrations from the main drive have decreased, making those from auxiliary drives more prominent. As a result, addressing audible noise and vibration in the design of auxiliary motors for automotive applications has become increasingly important. These compact drives, often located near passengers, are more audible compared to the main drive system. Consequently, they may produce vibrations that can excite neighboring structures or components, leading to noise-related concerns. Accurately measuring the structure-borne noise of permanent magnet motors presents a significant challenge. This paper introduces an innovative approach to enhance the precision of vibration measurement and differentiate between electromagnetic and mechanical sources of vibration, making it suitable for vibration measurements in sub-fractional horsepower motors. Furthermore, the proposed measurement methodology provides valuable information on the influence of design variations on vibration characteristics.

This paper proposes a novel technique for reducing force error angles in bearingless permanent magnet motors. Two-axis actively positioned bearingless motors generate a radial suspension force and torque with the suspension and motor windings, respectively. To achieve stable magnetic suspension, the suspension force should be precisely controlled. In contrast, undesired forces are generated due to the rotor radial displacement and the magnetic coupling between the motor and suspension fluxes. The force causes severe force error angles. Consequently, rotor vibrations occur, in the worst case, the rotor touches down on the stator. In this paper, the flux-strengthening control in the motor winding is proposed to reduce the force error angle. 3D-FEM analysis is used to illustrate the principle and present the calculation result. Furthermore, a prototype machine was fabricated, and it was demonstrated that the proposed method successfully reduced the force error angle in the experiment.

In the control system of brushless synchronous starter/generator, accurate information about the field current of MG is the paramount to achieve high dynamic and steady-state performance control. However, the traditional field current estimation (FCE) methods rely on the rotor position, when the position sensor fails, the actual field current cannot be obtained. To eliminate the limitation of rotor position and enhance reliability in field current estimation, a novel rotor position signal-free FCE method is presented. Firstly, the expression of estimated rotor currents of main exciter (ME) is derived and the relationship between the field current and estimated rotor current is analyzed. Then, by extracting the corner points of estimated ME rotor currents. the actual field current can be obtained without rotor position. Finally, the experiment result verifies the feasibility and effectiveness of the proposed method.

Permanent Magnet Synchronous Motors (PMSMs) offer advantages such as high output power and high efficiency. To further enhance their efficiency, control methods considering iron loss have been developed. However, few studies have directly measured iron loss due to the challenges involved, and even fewer have compared different control strategies based on direct measurements. This paper applies Repetitive Perfect Tracking Control (RPTC) to suppress iron loss caused by low-order harmonic currents in PMSMs. An H-coil method, which uses ingenious motor structure and data processing, is employed to directly measure magnetic field strength and magnetic flux density, thereby enabling iron loss measurement. Experimental results demonstrate that RPTC reduces iron loss compared to conventional PI control under varying load and speed conditions.

In direct current (DC) electrified railway systems, the substation output voltage serves as the reference voltage applied to the catenary system. Increasing the substation output voltage enhances the traction performance of vehicle traction motors, thereby reducing traction time and overall energy consumption. Conversely, reducing the substation output voltage hinders the train's voltage reaching the operating voltage required for light-load regenerative brake control. This can lead to an increase in unutilized regenerative energy. Therefore, a trade-off exists between energy-saving effectiveness. This study investigated the trade-off between the substation output voltage and the threshold voltage for light-load regenerative brake control and devised a method for determining the optimal substation output voltage.

The periodic output ripple of switching power supplies poses a significant challenge in noise-sensitive, high-precision signal processing circuitry used in high-performance wireless portable equipment. This paper presents an analysis of the impact of an ultra-high-frequency compact buck-type DC-DC converter on the electronic circuitry of portable devices. A class-A amplifier is used as a representative example of the electronic circuitry. We derive equations to analyze the fluctuations in the amplifier's signal output bias voltage caused by the converter's output ripple, allowing for a theoretical examination of the fundamental characteristics of these fluctuations. The output bias fluctuations of the amplifier are calculated using these equations and measured with an evaluation circuit board. The primary method for mitigating these output bias fluctuations is to reduce the converter output noise. Therefore, decreasing the ratio between the natural frequency of the inductor-capacitor (LC) filter and the switching frequency of the converter is effective. This reduction in ratio also facilitates the miniaturization of the converter. When the LC filter of the converter is miniaturized with values of 10nH and 10nF, the natural frequency is approximately 16MHz. By increasing the switching frequency to 1.6GHz, the fundamental component of the amplifier output bias voltage is suppressed to below 0.3mV.

Multicopters have attracted significant attention in recent years owing to their potential to revolutionize various fields. Maintaining stable flight in vertically narrow spaces is critical for broadening their applications. However, controllers designed for open environments often overlook pressure differentials that develop in confined spaces, thereby increasing the risk of ceiling collisions. To address this challenge, this study proposes a method for improving the feedback controllers of multicopters by employing the Robust Controller Bode (RCBode) plot. This intuitive loop-shaping technique enables the development of robust controllers using only classical control theory, a crucial consideration given that most commercially deployed multicopters rely on PID controllers. In addition, our approach avoids the substantial modeling efforts typically required to capture the complex dynamic characteristics of fluid flows by utilizing a simple nominal model capable of compensating for unknown external disturbances. Validation results demonstrate that multicopters equipped with the enhanced thrust controller can navigate vertically constrained spaces without ceiling collisions. Additionally, experimental findings confirm that tracking performance is improved not only by adjusting the thrust but also by reducing oscillations in roll and pitch.

One method of speed-sensorless vector control for induction motors involves estimating the stator angular velocity using the rotor-flux-induced voltage. This is known as the E2d method. We investigated how a first-order lag filter, applied to the q-axis component of the estimated rotor-flux-induced voltage stabilizes the system when employing the E2d method in automatic speed regulator (ASR). The filter plays a role in suppressing oscillations and extracting speed information. Traditionally, the oscillations that should be filtered are considered to be the lower-order harmonics. However, simulations have shown that a longer time constant is required, making it insufficient to simply remove the harmonics. We further conducted a root locus analysis using linear models, finding that the filter time constants capable of stabilization are dependent on the speed. Additionally, this paper presents design guidelines for filter time constants based on root locus analysis and reports on the experimental validation of the proposed criteria.

Partial shading and prolonged search time for determining maximum power point (MPP) are primary factors reducing power conversion efficiency in photovoltaic (PV) systems. This paperproposes a hybrid method that combines an improved horse racing algorithm (HRA) for global search with a gradient descent (GD) algorithm for precise MPP identification within the localized region. Simulation results demonstrate that the proposed approach achieves three key objectives: accurately location of the MPP; elimination of the steady-state oscillation amplitude; and significant reduction in the convergence time. Comparative analysis with incremental conductance (InC), perturbation and observation (P&O) methods confirms the superior performance of the hybrid approach under both partial shading and uniform irradiance conditions.

A power transistor utilizing a Darlington configuration of a Si-superjunction bipolar junction transistor (Si-SJBJT) as the main transistor and a Si-superjunction MOSFET (Si-SJMOSFET) as the auxiliary transistor, referred to as the Si full SJBMD, is proposed. A 10A sample of the full SJBMD with a breakdown voltage of 625V was developed, in which both the SJBJT die and the SJMOSFET one were assembly in a TO-247-4L package. The sample includes a main gate terminal, as well as an auxiliary gate terminal designed to extract stored charge from the main SJBJT during the turn-off operation. The V_CE(sat) at the rated current of the full SJBMD is 1.22V at room temperature. Increasing negative gate voltage in a charge extraction circuit connected to the auxiliary gate effectively decreases the power loss and delay time during the turn-off operation of the full SJBMD. Simulations compared the trade-off relationship between switching loss and on-state voltage of the full SJBMD with that of the competitive transistors. Additionally, impacts of the negative gate voltage in the charge extraction circuit on the SOA, as well as impacts of the shunt resistance connected between the auxiliary gate and emitter on the SOA and V_CE(sat) were clarified.

New configurations of the DC busbar are proposed, to reduce the total inductance of double-sided-cooling inverter. These include two low-inductance configurations of the DC wiring plates and DC terminals in the DC busbar. In configuration 1, the positive and negative DC terminals are branched, alternately arranged, and connected to the power module. In configuration 2, the DC wiring plates are branched and connected to the power module in parallel. Because the inverter has high dI/dt, the proximity effect fixes the distribution and flow of the commutating transient current during switching. Thus, it is difficult to reduce the inductance of the inverter even if the width and thickness of those wirings are changed. The proposed configurations overcome the influence of the proximity effect by utilizing parallel connection of the branched DC terminals or DC wiring plates. To estimate the low-inductance performances of these proposed configurations, the inductance equations were derived and their performances were evaluated. To validate the low-inductance performance, the prototype of the proposed inverter with configuration 2 was simulated and tested. These validation results indicate that the proposed inverter reduced the inductance to less than 15nH (from that of the conventional inverter 20nH) and achieved high efficiency in conjunction with high cooling performance.

Electrochemical energy storage systems function through the cooperative operation of batteries, power converters, and other components. Therefore, methodologies that coordinate electrochemical knowledge with power-system engineering are required to advance the system design and control of such systems. In this paper, a novel physics-based circuit simulation model of a lithium-ion battery is developed as a multi-domain analysis tool. In this model, ion conduction resistance, charge transfer resistance, and open-circuit potential are time-varying elements obtained by coupling a mathematical model to a transmission-line model of a porous electrode to enhance the physical principles in the equivalent circuit model. The model is implemented in a circuit simulator, and the actual measured constant-current charge/discharge curves at rates up to 10C are calculated with high accuracy. We use the circuit simulator to analyze the energy storage system model with a battery pack expanded from this model, a two-quadrant chopper, and a smoothing circuit. On the basis of electrochemical theory, we clarify the effect of the switching operation of the power converter in the system side on the current distribution inside the porous electrode.

This paper proposes a loss reduction method based on the single-pulse mode with a freewheeling period in V/f control for switched reluctance motors (SRMs), specifically targeting the high-speed region beyond the base speed. The proposed method is implemented using the pulse-width modulation (PWM) module of a general-purpose microcontroller, enabling an operation that closely mimics traditional single-pulse behavior while minimizing switching events. This method results in steeper rising and falling edges of the current waveform, contributing to reduced losses. Compared to conventional V/f control based on sinusoidal voltage drive, the proposed method shortens the conduction period in the negative torque region, thereby decreasing copper loss. Additionally, by introducing an appropriate freewheeling period, the voltage-time integral (i.e., flux) is reduced, leading to a reduction in iron loss. The proposed method consists of three main components: (A) a parameter determination strategy to enable single-pulse mode within the V/f control, (B) an efficient control technique tailored for freewheeling operation, (C) a method for suppressing beat phenomena caused by conduction angle errors in discrete-time control systems. Experimental results demonstrate that the proposed approach reduces copper loss by 21.4% and iron loss by 5.7% under base-speed and rated-torque condition, confirming its effectiveness.