Effects of low power electronics & computer equipment on power quality at distribution grid-measurements and forecast

The paper discusses power quality issues in case of simultaneous connection of a large number of low power nonlinear loads, like personal computers (PC), TV receivers, audio and video devices and similar electronic devices to the grid. Such consumers are at one-hand sensitive devices that require a stable and high quality of supply, but on the other hand they are sources of harmonics. Operation of a single PC, as a representative of such loads, is modeled using Matlab-Simulink software and verified by measurement performed in laboratory. The simultaneous operation of large number of PC-s is investigated by measurement on real site. The measurements are performed at several location connected to the grids with large number of PC type consumers (Computer Center) and other low power loads (highly populated residential area). The results are analyzed and compared with IEEE Standard 519 limits. In order to get the forecast of possible future situation, the developed model has been used for prediction of the "worst" case i.e. the highest possible harmonic level. It is shown that single PC is a significant source of harmonics. If a large number of PCs is connected to the grid, than they may present a serious threat to power quality, i.e. they can be a possible source of some negative effects.