Modeling of linear components for harmonic studies

This paper reviews the common practice and analytical models for the representation of aggregate linear load in harmonic propagation and distortion studies. The term linear load describes a class of loads, which, if supplied by a sinusoidal source at fundamental frequency, produce only fundamental sinusoidal current. The majority of residential and commercial loads, induction motors, and synchronous motors are examples of linear load. On the other hand, electronic loads, adjustable speed drives, and arc furnaces are non-linear loads, as they generate harmonics. Linear loads are a significant component of the system harmonic impedance. They constitute the main element of damping and they may affect the resonance conditions, particularly at higher frequencies. The harmonic modeling of linear load is sensitive to load size and composition. It is difficult to establish a model based on theoretical analysis. The necessity of practical measurements on distribution points together with detailed information of the network is vital for the derivation of a realistic model.