Flicker propagation in interconnected power systems

Voltage fluctuations leading to lamp flicker can propagate from the point of origin to various parts of the power system with some attenuation depending on the system impedances and load composition. Field measurements and theoretical studies suggest that the industrial loads containing large proportions of induction motors assist in attenuating flicker compared to residential loads consisting of passive devices. This paper describes a frequency domain approach which can be used to determine the propagation of voltage fluctuations when there are induction motor loads in the vicinity of the disturbing load. The method involves linearization of the network in d-q domain to evaluate various voltage transfer coefficients. Induction motor loads are modelled as a matrix of transfer functions developed between node voltages and currents. The proposed method has been applied to a simple meshed system and the results clearly show the influence of the induction motors on flicker attenuation and the dependency of the flicker transfer coefficient on the frequency of voltage fluctuations. Results are in close agreement with results obtained from time domain simulations.