Affiliations: [a] State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing, China | [b] Global Energy Interconnection Research Institute, Beijing, China
Correspondence:
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Corresponding author: Shuaibing Wang, State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China. Tel.: +86 15810237653; E-mail:shuaibingw@ncepu.edu.cn
Abstract: The operation conditions of series transformer in Unified
Power Flow Controller (UPFC) system are analyzed, and a shell-type
structural scheme is proposed in this paper. Taking into account the
nonlinear characteristic and the eddy current effect of the ferromagnetic
materials, the effective complex permeability is adopted to calculate the
nonlinear reluctance of the core, and an electromagnetic transient model of
the series transformer is presented based on the duality theory of electric
circuit and magnetic circuit, which is one key part of the comprehensive
simulation model of UPFC. Besides, the improved magnetic circuit method is
coupled with the electric circuit to analyze the special three-phase
asymmetrical DC bias phenomenon of series transformer. Some experiments
about no-load switching and asymmetrical DC bias on a low-voltage series
transformer prototype have been done to verify the transient model and the
improved magnetic circuit method, respectively. Finally, the reactive power
of the no-load series transformer prototype under asymmetrical DC bias is
calculated, the results indicate that the variation of the reactive power of
series transformer under asymmetrical DC bias becomes more complicated,
which increases the difficulty of voltage regulation in UPFC system.
Keywords: Series transformer, duality theory, complex permeability, asymmetrical DC bias, reactive power
