SIGNAL ANALYSIS IN POLLUTED POWER NETWORKS.

In the last decades, commercial electric customers have become increasingly interested in the relative quality of the power they purchase as their businesses rely more heavily on modern high-tech processes. The utilization of power electronic control elements causes unwanted grid perturbations, and therefore a reduction of the power supply quality. Spreading of harmonics is one of the main concerns, caused by switching actions of the power electronic control elements, and by voltage variations in the electrical grid. The mentioned grid perturbations lead to a functional impairment of the connected power electronic as well as electrical devices. In many applications, even small loads reduce power quality and lead to thermal overload of the whole appliance and a reduction of life time of single components, e.g. filter capacitors in converters. Power disturbances found on typical electric utility distribution systems degrade product quality, increase process downtime, and dissatisfy commercial customers. For this reason, monitoring the quality of the supply networks has become an issue of international interest. This paper describes the main power quality issues in electrical networks, aiming to investigate harmonic and interharmonic pollution from a modern approach. The beginning shows a theoretical description of the distortions occurring in power networks. The paper continues with a virtual instrument that detects harmonics, interharmonics and the fundamental frequency of the processed signal. The virtual instrument is based on signal processing techniques like Fourier and Hartley transforms and a fundamental frequency approximation algorithm. In the end, the test made with simulated perturbations will be described and the results will be discussed. [ABSTRACT FROM AUTHOR]