Michael Pepper

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.

A Zero-Voltage Switching Three-Port Isolated Full-Bridge Converter

This paper proposes an integrated single-stage three-port DC-DC converter. The proposed converter interfaces two bidirectional source/storage ports, and a galvanically isolated loading port. The power topology is based on the integration of a bi-phase boost pre-regulator stage into a phase-shift controlled full-bridge converter. The four bridge switches play the combined role of realizing synchronous boost conversion, and driving the transformer. The proposed topology is conditionally able to achieve zero-voltage switching of all bridge switches. Compared to the cascaded converter approach, this topology alleviates the cost overhead associated with introducing a switching leg for boost operation, and saves the switching loss it would exhibit. A constant-frequency switching scheme is adopted that presents two degrees of freedom necessary for proper control. The duty-cycle of the two phase-legs of the bridge is varied to control energy flow in the boost section, while the relative phase-shift between the legs is utilized to regulate the power pushed to the loading port. The operation of the topology is verified using an experimental 1 kW prototype, designed to handle a photovoltaic source, a storage battery bank, and a regulated DC load

Analysis and design for paralleled three-port DC/DC converters with democratic current sharing control

This paper presents a current sharing (CS) control structure for three-port DC/DC converters. Unlike regular two-port converters, three-port converters necessitate that two of three ports to have CS control simultaneously so that the third port achieves CS by default. The parallel operation of three-port converters for space applications requires a reliable CS structure to provide uniform current distribution among the modules. Both output port CS and battery port CS are achieved by paralleling CS loop and voltage regulation loop together according to the democratically elected maximum current reference. Stability is the main challenge for three-port paralleled systems as the added CS loops should not interact with abundance of control loops. Decoupled network and bandwidth limitation assumption are applied to ensure minimum loop interactions. Small signal analysis is applied to assess CS performance and judge system stability. The proposed CS structure is tested and verified by an experimental prototype.

An efficient solar charging algorithm for different battery chemistries

This paper proposes a new, effective, robust and reliable solar battery charging algorithm for the widely used batteries; NiCd, NiMH, Lead-Acid and Lithium-Ion. The algorithm has the ability to charge the battery in the outdoor conditions, when the power is variable, and terminate charging when the battery is fully charged. The algorithm has two modes of operation; current mode and voltage mode. It can deal with the unexpected outdoor conditions, which may cause drops in the current, without falsely detecting the battery state of charge. A programmable power supply was programmed and the four battery types were charged to test the algorithm.

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.

Interconnecting Microfluidic Package and Hybrid Interface for Chip-Based Sensor

In realizing a portable chemical analysis system, adequate partitioning of a reusable component and a disposable is required. For successful implementation of micromachined sensors in an instrument, reliable methods for interconnection and interface are in great demand between these two major parts. In this work we investigated interconnection methods of micromachined chip devices and hybrid fluidic interface system. The interconnection method based on micromachining and injection molding techniques was developed and an interconnecting microfluidic package was designed, fabricated and tested. For the hybrid interface, sequencing of the chemical analysis was examined and accordingly, syringe containers, a peristaltic pump and pinch valves were assembled to compose a reliable meso-scale fluidic control unit. The system using the interconnecting package and the hybrid interface was tested for a chip-based sensor.Copyright