Taehyung Kim

This work is focused on a solar photovoltaics (PV)-based onboard charger using reconfigured motor windings. In the proposed scheme, the motor windings and traction converter switches form a three-phase interleaved buck converter (IBC). The IBC is interfaced with the solar PV and acts as the maximum power point tracking converter. The IBC reduces the current ripple at the battery side and improves the battery cycle life. Through IBC, a large amount of current at the battery side is paralleled in three inductors of the IBC, which reduces the on-state losses in the switches and copper loss in the inductors. Therefore, it is possible to increase the power level of the onboard charging system as high as that of the propulsion system with enhanced compactness of the system while reducing the cost. Moreover, the applied control strategy reduces the current sensor requirements in IBC and eliminates the proportional–integral controller, which is another major advantage of the proposed system compared to conventional control of the IBC. Furthermore, the switches are subjected to zero current switching. Finally, the real-time experiment of the proposed system was accomplished using the OPAL-RT platform for 6 kW of charging power.

This article presents a versatile power converter and a hybrid energy source propulsion system for reliable, lightweight, and extended flight endurance unmanned aerial vehicles (UAVs). The proposed converter is designed to operate in various configurations to meet different flight mission requirements. It efficiently harvests power from solar panels, fuel cells, and a battery without requiring an additional converter in multiple working conditions. Furthermore, when the aircraft is in rest mode, the converter can act in power factor correction (PFC) converter mode. The proposed converter can minimize the number of components by integrating step-up and step-down operation capabilities as required for the objective. A BLDC (brushless DC) motor is used as the propulsion motor in the system because of its distinct benefits and unique features. Moreover, this work also discusses a unique technique to emulate the avionic load subsystem. The system is initially simulated using MATLAB/Simulink, and then it is verified on a real-time test bench.

This paper describes the unique full-scale bollard pull and self-propulsion tests of a large amphibious tracked military vehicle with two waterjet propulsors. To provide a reference for the self-propulsion and cavitation performance, a series of sea trials and bollard pull tests were performed in a military sea bay and in a large test basin, respectively. Good overall agreement between the sea trial and the computation was observed in the speed–power relationship. The cavitation-induced breakdown phenomenon was further explored via numerical simulations. The results indicated that the uncertainties in the numerical results were dominated by the scales of vapor bubbles. The analysis showed that the selection of the vapor bubble scale factors of 1.0 for growth and 0.05 for collapse were in good agreement with the experimental results. Rapid performance breakdown occurred when sufficient suction side-attached cavities were extended into the blade mid-chord and tip-board regions.

This work proposes an efficient configuration for light plug-in electric vehicles (PEVs) with a cost-effective and compact charging system. In this work, an integrated isolated DC-DC converter is investigated for a light PEV that employs a brushless DC (BLDC) machine as a traction motor to lower the component cost of the motor drive. The designed converter has the ability to function competently in all operating situations. The proposed converter has a minimum element because of the multi-functional operation of the converter. The designed converter can function as both maximum power point tracking (MPPT) and power factor correction (PFC) converters in solar and grid charging. In propulsion and regenerative braking operations, the proposed converter has buck/boost conversion capability to adjust the DC bus voltage according to vehicle speed to lower the inverter switching power losses and the traction motor's current ripple. As an outcome, the developed charging scheme becomes condensed and effective, making it a viable alternative for industry applications of light plug-in vehicles.

In this article, the design and control of an efficient solar-powered, reduced-stage water supply system with both grid and battery backup for enhanced reliability are presented. The water pumps with permanent magnet and induction motors have demagnetization and reliability issues under harsh environments. Therefore, a reduced-component four-phase switched reluctance motor drive is utilized to improve the cost-effectiveness and reliability of the system. The back-up battery together with the grid supply will contribute to the uninterruptable power supply of the standalone solar water pump. The provision to feed the solar power back into the grid can offer an additional benefit to the consumers: to earn revenue. A single-phase voltage source converter is employed to preserve the desired power quality at the grid side. In the proposed structure, an intermediate maximum power point tracking dc–dc converter for the solar panel is removed to make the system more compact and efficient. Based on the converter's absence, a new control scheme is developed and presented. MATLAB/Simulink-based simulation is carried out first to validate the developed system and control strategy. The simulation results are further validated through experimental results obtained via a developed prototype.

This article presents the development of an efficient and robust power management scheme for a grid-supported photovoltaic/battery configuration for a water pumping system employing a switched reluctance motor drive. The developed system structure and a modified notch filter (MNF) based control technique are combined and implemented through the H-bridge converter to maintain the power quality at the grid side and to improve the dynamic response of the overall system. The internal signals of the MNF are combined linearly to generate the control signal, resulting in a simpler control structure. Moreover, the proposed design can simplify the battery energy storage (BES) control to manage the BESs charging and discharging operations. The behavior of the developed system is examined through both simulation and experimental results and found adequate under all operational modes.

Although brushless excitation systems in synchronous machines have reduced the maintenance requirements and brush-related failures, they have increased the operating stresses on the excitation system components. Since the rotating excitation system is not accessible, it is difficult to detect excitation system failures such as open circuit diodes or open armature windings to prevent degradation in machine performance and reliability. Detection of such failures currently relies on monitoring the magnitude and harmonic content of the exciter field current. However, it is desirable to improve the reliability of fault detection with multiple test methods, considering the high cost of brushless exciter testing and repair due to the requirement of machine outage/disassembly. In this work, alternative off-line testing and on-line monitoring options are proposed for detection of excitation system failures. An off-line test based on ac excitation of the exciter field and on-line monitoring based on stator current and airgap flux analysis, are investigated, and fault indicators sensitive to excitation system failures are proposed for reliable fault monitoring. An experimental study on 3.8, 5.5, and 30 kW synchronous machines is given to validate the claims on the sensitivity and reliability of the proposed test methods.