Keywords: harmonics, load estimation, ZIP model, varying voltage, reactive power, power quality, nonlinear loads, distributed generation, power generation, power electronics, waveforms, combined loads
Characteristics of modern nonlinear loads and their influence on systems with distributed generation
Nonlinear electronic loads may demonstrate unexpected reactions to variations in power system voltage. This effect of the electrical load may be very significant in distributed generation power systems containing relatively small generators. This paper reviews modern nonlinear electronic load current consumption mechanisms and provides typical current waveforms. Based on extensive measurements and field surveys, modified ZIP models have been developed to produce descriptive behaviour for a large class of nonlinear loads that account for cutoff voltages. Finally, an independent PC program was developed to analyse individual load equipment under varying voltage conditions based on the active and reactive powers at the rated voltage. The program also enables the study of combined loads (such as in a single residential or commercial building).