Design of a power-electronic-assisted OLTC for grid voltage regulation

GR Chandra Mouli, P Bauer, T Wijekoon, A Panosyan, EM Bärthlein

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    High penetration of distributed generation (DG) has led to frequent voltage fluctuations in the distribution network. This paper describes the design of a partially rated, power-electronic-assisted onload tap-changing (OLTC) autotransformer. Positive and negative compensation of the grid voltage can be achieved on feeders that have high distributed generation and/or loading. A novel design of taps comprised of several no-load switches and a single semiconductor-mechanical hybrid switch have been proposed, that requires reduced voltage rating and a number of switches. In steady state, the mechanical switch in the hybrid switch conducts the load current resulting in low steady-state losses. During the tap change process, the OLTC uses semiconductor switches, namely insulated-gate bipolar transistor /metal-oxide semiconductor field-effect transistor, thus achieving arc-free tap change and long lifetime of switches. The OLTC system has been customized for both low-voltage and medium-voltage three-phase distribution networks. An open-delta configuration for the medium-voltage application has been proposed that requires only two OLTC units to control all three line voltages. Simulations are carried out to verify the steady-state and transient operation of the proposed OLTC.
    Original languageEnglish
    Pages (from-to)1086-1095
    Number of pages10
    JournalIEEE Transactions on Power Delivery
    Issue number3
    Publication statusPublished - 2015

    Bibliographical note

    Accepted Author Manuscript


    • Distributed power generation
    • four-step commutation
    • hybrid switch
    • onload tap changer (OLTC)
    • series compensation
    • transformer
    • voltage fluctuations


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