Harmonic Modeling of the Motor Side of an Inverter Locomotive

An AC-voltage source feeding an electric network results ina periodic excitation of the network. In steady state, allcurrents and voltages will be periodic with cycle time corresponding to thefrequency of the voltage source. If the network is linear, all signalsare sinusoidal and the network is solved using traditional methods.If the network contains components with nonlinear or switchingdynamics, iterative methods based on harmonic balance are oftenrequired to obtain the periodic steady state solution.By linearization of the system around the periodic solution, a lineartime periodic model is obtained. This can be used as a localdescription of the system in the neighborhood of the periodicsolution. If only periodic signals are considered, a linearizedmodel can be represented by a matrix, called the Harmonic Transfer Matrix(HTM).The method is applied to the motor side of a modern inverter train.Via the HTM, the steady state response to constant or periodicdisturbances or changes in reference values can be obtained