A frequency dependent circuit model of a wind turbine tower using transient response calculeted by FDTD

A method synthesizing a frequency-dependent equivalent model of a wind turbine tower for a circuit analysis is proposed in this paper. The model is derived from a transient response calculated by the Finite-Difference Time-Domain (FDTD) method. The FDTD method, which is one of electromagnetic field analysis methods, gives an accurate voltage and current responses including configurations of the tower and grounding electrode. The transient response is approximated in a time domain, and the result is converted to parameters of the Semlyen line model of the Electro-Magnetic Transients Program (EMTP). Pade method in z-domain is employed to automate the approximation. Once the transient response is represented by the equivalent circuit, transient analysis of the tower can be carried out without the time-consuming field analysis method.