Harmonic assessment using electromagnetic transient simulation and frequency-dependent network equivalents

Electromagnetic transient simulation can be used to model complex nonlinearities that are very difficult to represent adequately in the frequency domain. After reaching the steady state the voltage and current waveforms, represented by sets of discrete values at equally spaced intervals (corresponding with the integration steps), are subjected to fast Fourier transform processing to derive the harmonic spectra. However, the accuracy of the EMTP approach is limited by the restricted frequency dependence representation of the AC system components. It is shown that this problem is greatly reduced with the use of frequency-dependent network equivalents for the linear part of the system.