John Elmes

Maximum Energy Harvesting Control for Oscillating Energy Harvesting Systems

This paper presents an optimal method of designing and controlling an oscillating energy harvesting system. Many new and emerging energy harvesting systems, such as the energy harvesting backpack and ocean wave energy harvesting, capture energy normally expelled through mechanical interactions. Often the nature of the system indicates slow system time constants and unsteady AC voltages. This paper reveals a method for achieving maximum energy harvesting from such sources with fast determination of the optimal operating condition. An energy harvesting backpack, which captures energy from the interaction between the user and the spring decoupled load, is presented in this paper. The new control strategy, maximum energy harvesting control (MEHC), is developed and applied to the energy harvesting backpack system to evaluate the improvement of the MEHC over the basic maximum power point tracking algorithm.

System architecture of a modular direct-DC PV charging station for plug-in electric vehicles

Plug-in hybrid electric vehicles (PHEVs) are an emerging technology in the market and are helping to offset the negative effects of existing transportation methods that primarily rely on fossil fuel sources. As PHEVs are being introduced into the market, renewable energy sources such as solar power are taking a larger part in the energy sector. A need for high efficiency battery charging is required to decrease the amount of time it takes to charge these cars in order for them to become a viable means of transportation. A novel solar carport architecture is proposed that will provide a three port interface to PHEVs, solar panels and the utility grid to create a seamless power flow between the three ports. Current battery chargers rely heavily on AC/DC conversion from the grid to the car battery, however a direct DC/DC interface is made in this solar carport thus increasing the overall efficiency. This paper1 will prove this concept and show the improved performance over available battery charging schemes.

Investigation on inherently safe gate drive techniques for normally-on wide bandgap power semiconductor switching devices

Normally-on wide bandgap power semiconductor devices such as SiC JFET or GaN HFET demonstrate great promise for future power electronics applications, but suffer from power bus shoot-through concerns. This paper investigates new gate drive techniques to make the normally-on WBG devices inherently safe against potential power bus shoot-through failures. A fast-acting startup lockup protection circuit is proposed to derive power directly from the DC bus and generate a negative voltage to hold the WBG device in OFF mode. Simulation and experiment results show that the startup lockup source could generate −12V voltage within a few μs.

Bi-directional DCM DC to DC converter for hybrid electric vehicles

This paper presents a bi-directional DC to DC converter with a unique concept in control. The converter was designed for hybrid electric vehicles, so size becomes a pressing design parameter. For that reason a buck converter in DCM was used to realize the DC to DC converter. The DCM operation was used in order to shrink the magnetic components, as described in the paper. However, DCM converters are not inherently bi-directional. The unique controller developed here allows for the DCM converter to seamlessly direct power from low voltage side to high voltage side and from high voltage side back to low voltage side. A power management technique was also developed to handle a wide array of conditions present in hybrid electric vehicle applications. The technology developed here offers the designer the option to utilize the benefits of a buck converter in DCM while still maintaining a bi-directional power flow.

Modular bidirectional DC-DC converter for hybrid/electric vehicles with variable-frequency interleaved soft-switching

This paper presents a modular soft-switching bidirectional DC/DC converter for hybrid/electric vehicles. The converter operates in a variable-frequency quasi-square-wave (QSW) mode, which enables high efficiency, high switching frequency, and high power-density. The converter presented utilizes a new variable frequency interleaving approach which allows for each module to operate in an interleaved position while allowing for tolerance in inductance and snubber capacitor values. The variable frequency interleaved operation paired with high-efficiency soft-switching, a high-density inductor design, and optimal packaging results in a very high power-density converter. The 25 kW per module prototype converter exhibited power density greater than 8 kW/L, and peak efficiency over 97%, while operating with 100°C coolant.

A unity power factor, maximum power point tracking battery charger for low power wind turbines

This paper proposes a unique implementation of power factor correction (PFC) and maximum power point tracking (MPPT) for low power wind turbines. For a given wind condition, there is a unique electrical load which will harvest the maximum power from a wind turbine, the proposed control algorithm actively tracks this electrical loading condition for maximum power. An active 3-phase rectifier (VIENNA) converter is used to rectify the 3-phase AC voltage with near unity power factor which is critical in this application where the series resistance of the turbine is very high. An experimental 300W prototype was designed and tested to verify the design. Experimental results showed a significant increase in power extracted from the low power wind turbine when PFC and MPPT were implemented.

Low voltage flyback DC-DC converter for power supply applications

In this paper, we design a low voltage DC-DC converter with a flyback transformer. The converter will be used as a biased power supply to drive IGBTs. The flyback transformer using planar EI-core is designed and simulated using ANSYS PExprt software. Besides, anLT3574 IC chip from Linear Technology has been chosen for converter control. Finally, the converter modeling and simulation are presented and PCB layout is designed.

Reliability Characterization of Au–In Transient Liquid Phase Bonding Through Electrical Resistivity Measurement

Transient liquid phase (TLP) die-attach bonding is an attractive technique for high-temperature semiconductor device packaging. In this paper, the material reliability of gold-indium (Au-In) TLP bonding is investigated utilizing electrical resistivity measurement as an indicator of material diffusion. Samples were fabricated featuring a TLP reaction, representative of TLP die-attach, by depositing TLP materials on glass substrates with various Au-In compositions, but with identical barrier layers, and were then used for reliability investigation. The samples were annealed at 200 °C and then stressed with thermal cycling. Samples containing high indium content in the TLP bond are shown to have poor reliability due to material diffusion through barrier layers, whereas the samples containing sufficient gold content proved reliable through electrical resistivity measurement, energy-dispersive X-ray spectroscopy, focused ion beam, and scanning electron microscope characterization.