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Publications (7)0 Total impact

  • Article: Multilevel modular capacitor clamped DC-DC converter
    Faisal Habib Khan, L. M. Tolbert
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    ABSTRACT: A novel topology of multilevel modular capacitor clamped dc-dc converter (MMCCC) will be presented in this paper. In contrast to the conventional flying capacitor multilevel dc-dc converter (FCMDC), this new topology is completely modular and requires a simpler gate drive circuit. Moreover, the new topology has many advantageous features such as high frequency operation capability, low input/output current ripple, lower on-state voltage drop, and bi-directional power flow management. This paper discusses the construction and operation of the new converter along with a comparison with a conventional converter. Finally, the simulation and experimental results validate the concept of this new topology.
  • Article: Start-up and dynamic modeling of the multilevel modular capacitor-clamped converter
    Faisal Habib Khan, William E. Webb
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    ABSTRACT: This paper will present the analytical proof of concept of the multilevelmodular capacitor-clamped converter (MMCCC). The quantitative analysis of the charge transfer mechanism among the capacitors of the MMCCC explains the start-up and steadystate voltage balancing. Once these capacitor voltages are found for different time intervals, the start-up and steady-state voltages at various nodes of the MMCCC can be obtained. This analysis provides the necessary proof that explains the stable operation of the converter when a load is connected to the low-voltage side of the circuit. In addition, the analysis also shows how the LV side of the converter is (1/N)th of theHVside excitationwhen the conversion ratio of the circuit is N. In addition to the analytical and simulation results, experimental results are included to support the analytical proof of concept.
  • Article: Universal multilevel DC-DC converter with variable conversion ratio, high compactness factor and limited isolation feature
    Faisal Habib Khan, Leon M. Tolbert
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    ABSTRACT: A multilevel dc-dc converter with programmable conversion ratio (CR) is presented in this paper. This converter is a modified version of the MMCCC converter. A universal version of the MMCCC is developed in this paper, and the CR can be easily changed within a wide range. The MMCCC converter is based on capacitor-clamped topology, and the conversion ratio of the circuit depends on the number of active modules. However, like any other capacitor-clamped circuit, the MMCCC circuit requires a large number of transistors and capacitors to attain a high conversion ratio (CR). In this paper, a new circuit module will be introduced that can be connected in a cascade pattern to form the new converter. By using the new modular cell, it is possible to attain very high conversion ratio using a limited number of components, and thus more compactness compared to the predecessor MMCCC circuit can be achieved.
  • Article: Hybrid electric vehicle power management solutions based on isolated and nonisolated configurations of multilevel modular capacitor-clamped converter
    Faisal Habib Khan, William E. Webb
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    ABSTRACT: Abstract—This paper presents the various configurations of a multilevel modular capacitor-clamped converter (MMCCC), and it reveals many useful and new formations of the original MMCCC for transferring power in either an isolated or nonisolated manner. The various features of the original MMCCC circuit are best suited for a multibus system in future plug-in hybrid or fuel-cell-powered vehicles’ drive train. The original MMCCC is capable of bidirectional power transfer using multilevel modular structure with capacitor-clamped topology. It has a nonisolated structure, and it offers very high efficiency even at partial loads. This circuit was modified to integrate single or multiple high-frequency transformers by using the intermediate voltage nodes of the converter. On the other hand, a special formation of the MMCCC can exhibit dc outputs offering limited isolation without using any isolation transformer. This modified version can produce a high conversion ratio from a limited number of components and has several useful applications in providing power to multiple low-voltage loads in a hybrid or electric automobile. This paper will investigate the origin of generating ac outputs from the MMCCC and shows how the transformer-free version can be modified to create limited isolation from the circuit. In addition, this paper will compare various modified forms of the MMCCC topology with existing dc–dc converter circuits from compactness and component utilization perspectives.
  • Article: A 5 kW Bi-directional multilevel modular DC-DC converter (MMCCC) featuring built in power management for fuel cell and hybrid electric automobiles
    Faisal Habib Khan, Leon M. Tolbert
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    ABSTRACT: Abstract- A new capacitor clamped modular dc-dc converter with bi-directional power handling capability will be presented in this paper. This inductor-free design is modular, and it is possible to integrate multiple loads and sources simultaneously in the converter. Moreover, this 5 kW dc-dc converter can produce multiple ac outputs to feed power to ac loads get further control over the conversion ratio of the circuit. This high efficiency modular converter has flexible conversion ratio, and it could be successfully used in a multi-bus power system by virtue of its inherent power management properties.
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    Article: Multiple-load-source integration in a multilevel modular capacitor-clamped DC-DC converter featuring fault tolerant capability
    Faisal Habib Khan, L. M. Tolbert
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    ABSTRACT: A multilevel modular capacitor-clamped dc–dc converter (MMCCC) will be presented in this paper with some of its advantageous features. By virtue of the modular nature of the converter, it is possible to integrate multiple loads and sources with the converter at the same time. The modular construction of the MMCCC topology provides autotransformer-like taps in the circuit, and depending on the conversion ratio of the converter, it becomes possible to connect several dc sources and loads at these taps. The modularity of the new converter is not limited to only this dc transformer (auto) like operation, but also provides redundancy and fault bypass capability in the circuit. Using the modularity feature, some redundant modules can be operated in bypass state, and during some faults, these redundant modules can be used to replace a faulty module to maintain an uninterrupted operation. Moreover, by obtainin a flexible conversion ratio, the MMCCC converter can transfer power in both directions. Thus, this MMCCC topology could be a solution to establish a power management system among multiple sources and loads having different operating voltages.
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    Article: Generating isolated outputs in a multilevel modular capacitor clamped DC-DC converter (MMCCC) for hybrid electric and fuel cell vehicles
    Faisal Habib Khan, Leon M. Tolbert
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    ABSTRACT: This paper presents a new technique to obtain isolated dc voltage outputs from a capacitor clamped dc-dc converter. The multilevel modular capacitor clamped converter (MMCCC) has several key features that make it possible to generate ac outputs (10 kHz) from a dc-dc converter circuit. Using those high frequency ac outputs, the MMCCC circuit can incorporate single or multiple high frequency transformers to generate isolated ac outputs. These isolated outputs can be rectified and filtered to obtain unidirectional or bi-directional dc outputs. Using another MMCCC converter stage or an active full bridge block, the ac port can be made bi-directional to transfer power in both directions. By adopting the MMCCC topology to achieve isolated outputs, it is possible to simultaneously integrate multiple dc sources in an isolated and non-isolated manner. This paper will investigate the origin of the ac outputs in the MMCCC circuit, and present an analytical approach to estimating the isolated dc output voltage. Finally, experimental results will be presented for further verification of the concept.