Accuracy problems in on-line one-phase distribution/load system identification task

The paper deals with accuracy problems of single-phase power distribution systems and load identification for harmonic frequencies under the assumption of user access to common load/distribution system terminals. The load is assumed to be permanently connected to the power system. This assures fixed working points for nonlinear/switched loads, allowing identification of their equivalent linear parameters. The equivalent harmonic sources (levels, phases) and impedances for harmonic frequencies of the distribution system and the customer load are of interest. The identification is based on two observations of system/load currents and voltages as they appear on the common system/load terminals under natural and disturbed power system states. Due to the rigid system behaviour, caused by the low level of distribution system impedance and due to the presence of strong fundamental voltage/current components, there is a limited choice of useful realisable system disturbances. Two disturbing methods, passive and active, were considered