Least Squares Modeling of Voltage Harmonic Distortion Due to PC Cluster Operation

Regarding the possibility of harmonic generation, personal computers (PCs) are very significant within the category of non-linear low power loads. In modern distribution systems, the number of PCs simultaneously connected to distribution grid constantly increases. This PC clustering can negatively affect the quality of supply. The paper deals with mathematical modeling of the voltage total harmonic distortion (THDU) caused by operation of PC cluster. The proposed model is based on the power quality measurements carried out in a computer centre and computer simulations. It takes into account the THDU dependence on the PC cluster size and grid stiffness. Model parameters are derived in the least squares sense. The influences of cable cross-section and pre-existing THDU of the phase voltage are also discussed. The accuracy of the proposed model is confirmed by additional measurements performed in a commercial building