Novel Single-Core Phase-Shifting Transformer: Configuration, Analysis and Application in Loop Closing

Yong Xu (), Fangchen Huang, Yu Diao, Chongze Bi, Xiaokuan Jin and Jianhua Wang
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Yong Xu: State Grid Yangzhou Power Supply Company, Yangzhou 225009, China
Fangchen Huang: State Grid Yizheng Power Supply Branch Company, Yangzhou 211400, China
Yu Diao: State Grid Yizheng Power Supply Branch Company, Yangzhou 211400, China
Chongze Bi: School of Electrical Engineering, Southeast University, Nanjing 210096, China
Xiaokuan Jin: School of Electrical Engineering, Southeast University, Nanjing 210096, China
Jianhua Wang: School of Electrical Engineering, Southeast University, Nanjing 210096, China

Energies, 2025, vol. 18, issue 17, 1-15

Abstract: Phase-shifting transformers (PST) are widely used to control power flows. However, conventional designs can vary only the phase angle, leaving the voltage magnitude unaffected or requiring structurally complex devices. This study proposes a compact PST topology that realizes simultaneous, decoupled control of both voltage magnitude and phase angle through two coordinated sets of windings. Closed-form equations are derived to link the phase-shifting and voltage regulation windings turn ratios to any target magnitude ratio and phase-shift angle, providing a unified design framework that guarantees the full practical operating range. Steady-state tests verify that the device can change the phase or adjust the magnitude independently without cross-coupling. Dynamic tests demonstrate that, when a tap command is issued, the line currents and active power converge to new set-points within a few fundamental periods and with minimal oscillation. Furthermore, the PST’s application to loop closing operations in 220 kV networks is investigated, where simulation results show it can suppress loop closing currents by over 90% under adverse voltage mismatch conditions. These results confirm that the proposed PST offers a fast, economical alternative to Flexible AC Transmission Systems (FACTS) equipment for real-time power flow balancing, renewable integration and inter-area exchange in modern transmission networks.

Keywords: phase-shifting transformer; power flow; flexible alternating current transmission systems; phase-angle control; loop closing (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2025
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