Small Distributed Renewable Energy Generation for Low Voltage Distribution Networks

Driven by the existing energy policies, the use of renewable energy has increased considerably all over the world in order to respond to the increasing energy consumption and to reduce the environmental impact of the electricity generation. Although most policy makers and companies are focusing on large applications, the use of cheap small generation units, based on local renewable resources, has become increasingly attractive for the general public, small farms and remote communities. The paper presents several results of a research project aiming to identify the power quality issues and the impact of RES based distributed generation (DG) or other non-linear loads on low voltage (LV) distribution networks in Romania; the final goal is to develop a Universal Power Quality Conditioner (UPQC) able to diminish the existing disturbances. Basically, the work analyses the existing DG technologies and identifies possible solutions for their integration in Romania; taking into account the existent state of the art, the attention was paid on small systems, using wind and solar energy, and on possibility to integrate them into suburban and rural LV distribution networks. The presence of DG units at distribution voltage level means the transition from traditional passive to active distribution networks. In general, the relatively low penetration levels of DG does not produce problems; however, the nowadays massive increase of local power generation have led to new integration challenges in order to ensure the reliability and quality of the power supply. Power quality issues are identified and their assessment is the key element in the design of measures aiming to diminish all existing disturbances

Analysis of the Steinmetz compensation circuit with distorted waveforms through symmetrical component-based indicators

This paper deals with the use of a set of indicators defined within a symmetrical component-based framework to study the characteristics of the Steinmetz compensation circuit in the presence of waveform distortion. The Steinmetz circuit is applied to obtain balanced currents in a three-phase system supplying a single-phase load. The circuit is analyzed without and with harmonic distortion of the supply voltages. The compensation effect is represented by the classical unbalance factor and by the Total Phase Unbalance (TPU) indicator defined in the symmetrical component-based framework. Comparing the two indicators, it is shown that the classical unbalance factor is insufficient to represent the effect of voltage distortion and fails to detect the lack of total unbalance compensation occurring with distorted waveforms. Correct information is provided by calculating the TPU indicator. © 2009 IEEE

Software Tool for Real-Time Power Quality Analysis

A software tool dedicated for the analysis of power signals containing harmonic and interharmonic components, unbalance, voltage dips and voltage swells is presented. The software tool is a virtual instrument, which uses innovative algorithms based on time and frequency domains analysis to process power signals. In order to detect the temporary disturbances, edge detection is proposed, whereas for the harmonic analysis Gaussian filter banks are implemented. Considering that a signal recovery algorithm is applied, the harmonic analysis can be made even if voltage dips or swells appear. The virtual instrument input data can be recorded or online signals; the last ones being get through a data acquisition board. The virtual instrument was tested using both virtually created and real signals from measurements performed in distribution networks. The paper contains a numeric example made on a synthetic digital signal and an analysis made in real-time