In this study, we propose a three-phase wireless power transfer system implementing unbalanced-current control with zero-phase current. The control allows uniform power transfer with maximum transfer efficiency regardless of the receiver coil position. The control is applied to the circuit configuration with an inductor in zero-phase, which can cancel the mutual inductances between the phase-coils in the transmitter. The experiments with a prototype of the three-phase wireless power transfer coil for automatic guided vehicle (AGV) confirm that the system implementing the control can perform uniform and efficient power transfer to an AGV irrespective of whether it is moving or at standstill.

A bidirectional onboard DC/DC converter that can be used to rapidly charge an electric vehicle (EV) or feed EV battery power to a DC microgrid based on application requirements is proposed. This system concept is labeled as an onboard fast battery charging EV (cEV). Interestingly, owing to the presence of the inbuilt quick EV charger, external high power chargers are not required for fast charging applications. The proposed autonomous control strategy may also aid in DC grid voltage stabilization within the permissible range of 360V to 400V when power is being transferred from a PV to DC bus by controlling the DC/DC converter for PV and the DC multi power unit (DCMPU) independently. The DCMPU can also control both the power or DC bus voltage based on system requirements. Next, a droop-based control is implemented in the DCMPU to avoid mutual interference in the controllers. Detailed simulation studies are performed in MATLAB/Simulink to demonstrate the effectiveness of the proposed system. Overall, the proposed system helps maintain DC bus voltage fluctuations within a permissible range.

A linear motor that uses a finite length Halbach array as its magnetic field causes a thrust force ripple owing to end effects. In this paper, the theoretical and numerical analysis methods of the Halbach array are investigated. The results of the electromagnetic field analysis are compared to confirm the validity of the theoretical and numerical solutions. Moreover, we focus on the magnetic pole period and coil arrangement of the finite length Halbach field type linear motor to eliminate the influence of the end effects, and report the relationship with the end effects.

Dual three-phase motors offer numerous advantages, including the elimination of 6th-order torque ripple. However, they have the drawback of generating large harmonic currents when driven because of their small inductance for specific harmonics. In this study, inductance, which depends on the winding structure and harmonics, is formulated using the winding factor in order to reduce harmonic currents through winding design. The theoretical values of the formulated inductance are in good agreement with the FEA values. In addition, the magnitude of the harmonic currents generated during drive are quantitatively evaluated using these inductance values. Conventionally, when the winding factor for the 5th and 7th spatial harmonics is small, the 5th and 7th harmonics of back EMF can be reduced. However, dual three-phase motors with small winding factor for 5th and 7th spatial harmonics have the disadvantage of having very small inductance for specific harmonics, resulting in large harmonic currents.

This paper proposes a new modulation method for modular multilevel cascade converter-based active power filters (MMC-APFs). The proposed modulation method uses the same pulse width modulation (PWM) controller as a traditional bipolar modulation method, and the generated PWM signals are interchanged among the bridge cells. This method makes it possible to shift the carrier phase angle between two switching legs in one cell, reducing the ripple current through the cell capacitor without increasing the number of PWM channels. This is important to reduce the cost of the control circuit, especially in low-voltage applications of MMCs. An experimental circuit of a 3.3kVA MMC-APF demonstrates a 20% reduction in the ripple current and a 38% reduction in the power loss in the cell capacitor.

This paper proposes four new generalized orthogonal matrices that can be used for orthogonal transformation in six-phase motors. This transformation, which is also called vector space decomposition (VSD), is essential for the control of six-phase currents contaminated by harmonics and/or high-speed mode component. Most importantly, the proposed generalized orthogonal matrices have the potential to enable new development in the current control of six-phase motors.

Our research focuses on power electronics and motor control. In this document we present our research topics.