Abstract
A three-phase five-limb transformer is a potential application form of the Sen Transformer (ST), especially for the scenarios with significantly unbalanced load conditions. This paper proposes a quasi-steady-state model of three-phase five-limb ST (TPFLST) based on duality. Firstly, an equivalent circuit model that takes into account the eddy current effect and the coupling effect involving the magnetic circuit can be derived according to the equivalent magnetic circuit of the TPFLST. The iron-core of the TPFLST may be represented by the parallel combination of the resistances reflecting the power loss of the iron-core and the saturable inductances considering the ferromagnetic hysteresis in virtue of the principle of duality. Subsequently, an electric circuit model of the voltage and current of each winding for the TPFLST is able to be accomplished on the basis of the electrical connection between the TPFLST and the external systems in accordance with Kirchhoff’s voltage and current law. Consequently, a quasi-steady-state model of the TPFLST which considers the coupling relationship involving the magnetic and electric circuits can be formed by combining the equivalent circuit model and the electric circuit model. With the help of MATLAB, the effectiveness of the proposed model may be verified by comparing the results about power flow control including power, voltage, and current with the ones from the existing literature. Furthermore, the TPFLST is found to be better-suited for the unbalanced load condition according to a comparison among the unbalanced degrees of output currents for the STs with different core structures under unbalanced load conditions.
Highlights
The demand for electricity of the power system makes the transition into renewable energy sources an inevitable choice due to the rising prices of energy, fossil fuel depletion, and the increasing concerns about the environment [1,2,3]
This paper proposes a quasi-steady-state model for the three-phase five-limb ST (TPFLST) using the principle of duality, which takes into consideration of the eddy current effect and the coupling effect involving the magnetic circuit
There is a good agreement about the series-compensating voltage and the secondary-side current between the results from the proposed model and the ones obtained in the existing literature
Summary
The demand for electricity of the power system makes the transition into renewable energy sources an inevitable choice due to the rising prices of energy, fossil fuel depletion, and the increasing concerns about the environment [1,2,3]. From the perspective of the modeling method for transformer, there are mainly two types of methods, i.e., the principle of duality-based method and the unified magnetic equivalent circuit (UMEC) based method. A detailed transformer model using duality was established in [22], which considered the topological structures of iron-core, air gap, and tank. In accordance with the principle of duality, the equivalent circuit model of TPFLST may be a complex combination of ideal transformers, resistances, and inductances. The contributions of this paper are (1) A quasi-steady-state model of the ST with three-phase five-limb iron-core structure is proposed.
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