Gokhan Sen

Bio: Gokhan Sen is an academic researcher from Technical University of Denmark. The author has contributed to research in topics: Boost converter & Inductor. The author has an hindex of 7, co-authored 14 publications receiving 213 citations. Previous affiliations of Gokhan Sen include University of Copenhagen & University of Akron.

Analysis and Design of Fully Integrated Planar Magnetics for Primary–Parallel Isolated Boost Converter

Abstract: A highly efficient planar integrated magnetic (PIM) design approach for primary-parallel isolated boost converters is presented. All magnetic components in the converter, including two input inductors and two transformers with primary-parallel and secondary-series windings, are integrated into an E-I-E-core geometry, reducing the total ferrite volume and core loss. The transformer windings are symmetrically distributed into the outer legs of E-cores, and the inductor windings are wound on the center legs of E-cores with air gaps. Therefore, the inductor and the transformer can be operated independently. Due to the low-reluctance path provided by the shared I-core, the two input inductors can be integrated independently, and also, the two transformers can be partially coupled to each other. Detailed characteristics of the integrated structure have been studied in this paper. AC losses in the windings and the leakage inductance of the transformer are kept low by interleaving the primary and secondary turns of the transformers substantially. Because of the combination of inductors and transformers, the maximum output power capability of the fully integrated module needs to be investigated. Winding loss, core loss, and switching loss of MOSFETs are analyzed in-depth in this work as well. To verify the validity of the design approach, a 2-kW prototype converter with two primary power stages is implemented for fuel-cell-fed traction applications with 20-50-V input and 400-V output. An efficiency of 95.9% can be achieved during 1.5-kW nominal operating conditions. Experimental comparisons between the PIM module and three separated cases have illustrated that the PIM module has advantages of lower footprint and higher efficiencies.

Voltage and Current-Programmed Modes in Control of the Z-Source Converter

Abstract: The Z-source converter (ZSC) is an alternative power conversion topology that can both buck and boost the input voltage using passive components with improved reliability. Dynamic modeling of the ZSC from different perspectives has been studied. So far, based on these models, the dc-link voltage is controlled using direct measurement, or through measurement of the capacitor voltage. In this paper, two methods of dc-link voltage control of ZSC are analyzed and compared. Both methods are based on measuring the input voltage and state variables of the ZSC and designing a compensator based on the converter state space averaged model. Voltage mode (VM) and current-programmed mode (CPM) controls are derived based on the ideal small-signal model of the Z-source network with inductive loading. Nonminimum phase characteristics caused by the right half-plane zero in the control-to-capacitor-voltage transfer function are minimized by designing proper compensators in both VM and CPM controls. In CPM, since the order of the system reduces by one, it is possible to achieve similar dynamic performance with a simpler compensator. Performance of both control methods of the compensated ZSC are verified by simulation and experimental results for input and load disturbances.

Voltage and Current Programmed Modes in Control of the Z-Source Converter

Abstract: The Z-source converter (ZSC) is an alternative power conversion topology that can both buck and boost the input voltage with improved reliability. Dynamic modeling of the ZSC from different perspectives has been studied. Based on these models, the dc-link voltage is controlled using direct measurement or measurement of the capacitor voltage. In this paper, two methods of dc-link voltage control of ZSC are analyzed and compared. Both methods are based on measuring the input voltage and the capacitor voltage to estimate the peak of the dc link voltage. Compensator for both voltage mode (VM) and current programmed mode (CPM) controls were designed based on the state space averaged signal model of the ZSC with inductive loading. In CPM, since the order of the system is reduced by one, it is possible to achieve similar dynamic performance with a simpler compensator. Performance of both control methods of the compensated ZSC are verified by simulation and experimental results for input and load disturbances.

Fully integrated planar magnetics for primary-parallel isolated boost converter

Abstract: A high efficient planar integrated magnetics (PIM) design approach for primary parallel isolated boost converters is presented. All magnetic components in the converter including two input inductors and two transformers with primary-parallel and secondary-series windings are integrated into an E-I-E core geometry. Due to a low reluctance path provided by the shared I-core, the two transformers as well as the two input inductors can be integrated independently, reducing the total ferrite volume and core loss. AC losses in the windings and the leakage inductance of the transformer are kept low by interleaving the primary and secondary turns of the transformers. To verify the validity of the design approach, a 1-kW prototype converter with two primary power stages is implemented for a fuel cell fed battery charger application with 20–40 V input and 170–230 V output. An efficiency of 96% can be achieved during nominal operating conditions. Also experimental comparisons between the PIM module and two separate cases have been done in order to illustrate the advantages of the proposed method.

A new method for start-up of isolated boost converters using magnetic- and winding-integration

Abstract: A new solution to the start-up and low output voltage operation of isolated boost family converters is presented. By the use of integrated magnetics and winding integration, the transformer secondary winding is re-used during start-up as a flyback winding coupled to the boost inductor. The traditional added flyback winding coupled to the boost inductor is thus eliminated from the circuit, bringing substantial cost savings, increased efficiency and simplified design. Each subinterval of the converter operation is described through electrical and magnetic circuit diagrams, and the concept is extended to other isolated boost family topologies. The principle of operation is demonstrated with a 800W isolated boost prototype, and a 1600W primary parallel series secondary isolated boost converter. Efficiency measurements of both prototypes are presented, including measurements during both start-up and normal boost operation.

Impedance-Source Networks for Electric Power Conversion Part I: A Topological Review

Abstract: Impedance networks cover the entire of electric power conversion from dc (converter, rectifier), ac (inverter), to phase and frequency conversion (ac-ac) in a wide range of applications. Various converter topologies have been reported in the literature to overcome the limitations and problems of the traditional voltage source, current source as well as various classical buck-boost, unidirectional, and bidirectional converter topologies. Proper implementation of the impedance-source network with appropriate switching configurations and topologies reduces the number of power conversion stages in the system power chain, which may improve the reliability and performance of the power system. The first part of this paper provides a comprehensive review of the various impedance-source-networks-based power converters and discusses the main topologies from an application point of view. This review paper is the first of its kind with the aim of providing a “one-stop” information source and a selection guide on impedance-source networks for power conversion for researchers, designers, and application engineers. A comprehensive review of various modeling, control, and modulation techniques for the impedance-source converters/inverters will be presented in Part II.

Impedance-Source Networks for Electric Power Conversion Part II: Review of Control and Modulation Techniques

Abstract: Impedance-source networks cover the entire spectrum of electric power conversion applications (dc-dc, dc-ac, ac-dc, ac-ac) controlled and modulated by different modulation strategies to generate the desired dc or ac voltage and current at the output. A comprehensive review of various impedance-source-network-based power converters has been covered in a previous paper and main topologies were discussed from an application point of view. Now Part II provides a comprehensive review of the most popular control and modulation strategies for impedance-source network-based power converters/inverters. These methods are compared in terms of theoretical complexity and performance, when applied to the respective switching topologies. Further, this paper provides as a guide and quick reference for researchers and practicing engineers in deciding which control and modulation method to consider for an application in a given topology at a certain power level, switching frequency and demanded dynamic response.

Γ-Z-Source Inverters

Abstract: Voltage-type Γ-Z-source inverters are proposed in this letter. They use a unique Γ-shaped impedance network for boosting their output voltage in addition to their usual voltage-buck behavior. Comparing them with other topologies, the proposed inverters use lesser components and a coupled transformer for producing the high-gain and modulation ratio simultaneously. The obtained gain can be tuned by varying the turns ratio $\gamma _{\Gamma Z} $ of the transformer within the narrow range of $1 . This leads to lesser winding turns at high gain, as compared to other related topologies. Experimental testing has already proven the validity of the proposed inverters.

Overview of Planar Magnetic Technology—Fundamental Properties

Abstract: The momentum toward high efficiency, high frequency, and high power density in power supplies limits wide use of conventional wire-wound magnetic components This paper gives an overview of planar magnetic technologies with respect to the development of modern power electronics The major advantages and disadvantages in the use of planar magnetics for high-frequency power converters are covered, and publications on planar magnetics are reviewed A detailed survey of winding conduction loss, leakage inductance, and winding capacitance for planar magnetics is presented so power electronics engineers and researchers can have a clear understanding of the intrinsic properties of planar magnetics

Generalized multi-cell switched-inductor and switched-capacitor Z-source inverters

Abstract: High performance voltage and current-source inverters (VSI and CSI) are widely required in various industrial applications such as servo-motor drives, special power supplies, distributed power systems and hybrid electric vehicles. However, the traditional VSI and CSI have been seriously restricted due to their narrow obtainable output voltage range, short-through problems caused by misgating and some other theoretical difficulties due to their bridge-type structures. The Z-source inverter was proposed to overcome the problems associated with the traditional inverters, in which the functions of the traditional dc-dc boost converter and the bridge-type inverter have been successfully combined. To further widen the operational range or gain of the Z-source inverter in both the voltage and current type configurations, the generalized switched-inductor and switched-capacitor impedance networks are proposed hereon. Both simulation and experimental testing have been conducted for validating the extra boosting introduced with some representative results captured and presented near the end of the paper.