A Transformer Three-Phase Modeling Method for Power Grid Asymmetrical Power Flow Calculation

Abstract

The invention discloses a three-phase transformer modeling method for asymmetrical load flow calculation of a power grid. A circuit model with an ideal three-phase transformer in serial connection with an impedor is adopted, a two-port definition is generalized to establish mathematic models of a Y-parameter matrix, block elements of the Y-parameter matrix can be calculated by a method resolving primary-side and secondary-side current by means of sequential zero setting of primary-side and secondary-side voltage, the mathematic models for different o'clock times in a same group are unified via a relative o'clock-time transformational matrix, addition items are added via a phase line transformational matrix to correct a matric including Y-parameters of a D-type winding transformer so as to avoid singularity, and finally nine groups of block element calculation formulae covering fifty-four Y-parameter matrixes of a three-phase transformer are obtained. The three-phase transformer modeling method has the advantages that the established circuit model is capable of directly reflecting a transformation process and influences of leakage flux and a zero-sequence excitation impedance; repeated modeling of the transformer for different o'clock times is needless by the aid of the relative o'clock-time transformational matrix; by the aid of a method for solving the problem of singularity of the Y-parameter matrixes by adding the addition items through the phase line transformational matrix, special processing is no longer needed during load flow calculation.

Description

technical field [0001] The invention belongs to the technical field of power system analysis. Background technique [0002] For a long time, the power system has been analyzed and calculated based on the three-phase approximately symmetrical condition using a single-phase model. However, in recent years, the transmission network and distribution network have made great progress, and the scene of asymmetric operation of the power grid will become more and more common. In the high-voltage transmission network, even under the condition that the loads are three-phase symmetrical, the incomplete transposition of the three-phase lines will still lead to system asymmetry. In the medium and low voltage distribution network, with the maturity of technologies such as micro-grid, active distribution network and new energy power generation, the large-scale access of distributed power will be greatly promoted. The impact of single-phase high-power new energy generation / power consumption...

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