Three winding transformer s-domain model for modal analysis of electrical networks

This paper describes an s-domain sequence model for three winding transformers to be used in modal analysis of ac networks. The model takes into account off-nominal tap positions and the phase shifts among the windings. The main contribution of this proposed model is to complete the set of s-domain models of electrical system components already developed (loads, transmission lines, generators, harmonic filters, shunt elements) suitable for modal analysis of complex electrical networks. Modal analysis provides an important set of system information that is hard to be obtained using the conventional time simulation and frequency response methods. This information may be effectively used to improve the harmonic performance of electrical networks, to build linear equivalents for harmonic and electromagnetic transient studies and to perform linear dynamic performance analysis.