Advanced methodologies and new tool for multiphase power quality analysis & mitigation

For utility network and end-user loads harmonic simulation, a large number of power quality problems show that single phase equivalent circuit and linear model are not suitable to reveal a part of real disturbance events such as unbalance harmonic impedances, asymmetric voltage sag, negative sequence current propagation, and phase to ground harmonic resonance. This paper deals with some particulars aspects of multiphase network harmonic modelling used in ExpertEC©, a new and simple power quality analysis tool developed by Electricite de France (EDF). It makes power quality mitigation easier and it can shorten substantially the studying time of a real power quality problem, compared with a more general simulation software. As ExpertEC uses true multiphase matrix models, it can deal with all the above phenomena by means of its simple and useful industrial loads and sources models. For usual end-user loads such as squirrel cage induction motors, power transformers and lines, full multiphase matrix models are employed in order to characterize positive, negative and zero sequence impedances. These modules make it possible to simulate unbalance voltage impact to an induction machine as it draws important negative sequence currents from the power supply when its input voltage is unbalanced.