Yu Zhang

Huazhong University of Science and Technology, Wu-han-shih, Hubei, China

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Publications (5)1.71 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this article a novel controllable reactor based on regulating the transformer's primary equivalent impedance by controlling its secondary voltage source inverter load is proposed. When the secondary current of a transformer is forced to be proportional to and in inverse phase with its primary current, the primary side of the transformer exhibits a linear adjustable reactance with respect to the proportion coefficient. The voltage source pulse width modulation (PWM) inverter connected to the secondary side of the transformer provides the required secondary current. In order to realise a large-capacity reactor, a transformer with multiple secondary windings is used to reduce the capacity requirement of each PWM inverter. A large-capacity (800 kVA) prototype is fabricated. The experimental results verify the characteristics of the novel controllable reactor – linear reactance tuning, few harmonics and fast response.
    International Journal of Electronics 01/2011; 98(1):25-40. · 0.51 Impact Factor
  • Yu Zhang, Qiaofu Chen, Jun Tian
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    ABSTRACT: With the primary and a secondary winding ports leading out, a multi-winding transformer with air-gapped core can be regarded as a linear two-port network. Adjust the current relationships between the ports, the input impedance of the primary winding can be a variable reactance; change the short-circuit conditions of other secondary windings, the reactance of primary winding will move in deferent intervals. With proper designing, these intervals can be jointed, so the reactance can be regulated continuously in a wide area. The controllable reactor based on this principle, whose power rating is determined by short-circuit capacity mainly, can adopt the low-rating pulse-width-modulation (PWM) inverters to accomplish the port adjusting.
    Electrical Machines and Systems, 2008. ICEMS 2008. International Conference on; 11/2008
  • Yu Zhang, Qiaofu Chen, Lu Cheng
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    ABSTRACT: In this paper, a novel high-power controllable reactor based on magnetic flux compensation (CRMFC) is described. A structure of multiple-winding transformer is adopted to realize high-power application in power utilities. Meanwhile, a series of middle-level PWM-inverter units are employed to generate compensating current. The principle of the multiple-windings compensation is revealed and a practical control strategy is proposed. A rated 6 kV, 800 kVA prototype is fabricated and the experimental results verify the feasibility of the whole scheme, as well as the excellent characteristics of the proposed controllable reactor.
    Electrical Machines and Systems, 2007. ICEMS. International Conference on; 11/2007
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    ABSTRACT: A conceptual design of a 3000 kVA high-temperature superconducting (HTS) transformer with split types of windings for locomotives is developed in this paper. The primary winding of it has four coils which are arranged on two core limbs respectively and connected in parallel, so the branch currents are probably not equal to each other. In this paper, on the basis of the 3-D magnetic field analysis by finite element method (FEM), an inductance matrix (IM) for multi-branch of the primary winding and one of the secondary split windings is first calculated, and then the circulating current among the primary branches is determined by circuit theory. Finally, the short-circuit impedance between the primary winding and one of the secondary split windings is obtained.
    01/2007;
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    ABSTRACT: In a high-temperature superconducting (HTS) transformer, the leakage magnetic field decreases the critical current and increases the ac loss in the tapes. Moreover, because of nearly zero resistance of HTS tapes, a slight unbalance of the branch inductances of the windings might result in heavy circulating current. So, the numerical analysis of the leakage magnetic field and circulating current is especially necessary for an HTS transformer design. In this paper, the influence of the winding configurations on the stray field and circulating current is studied. That is, the magnetic field distribution is analyzed by finite-element method and then, based on the inductance matrix obtained after a magnetic field analysis, the circulating current is calculated by circuit analysis. Some measures for improving the leakage field and circulating current distribution are also proposed to make HTS transformers more efficient.
    IEEE Transactions on Applied Superconductivity 10/2005; · 1.20 Impact Factor

Publication Stats

6 Citations
1.71 Total Impact Points

Institutions

  • 2007–2011
    • Huazhong University of Science and Technology
      • Department of Electrical Machinery and Control
      Wu-han-shih, Hubei, China