Analiza kvaliteta električne energije na satnom nivou kod priključenja elektrana na obnovljive izvore energije

Abstract

Analyses necessary for the new power plant connection contain the following power quality analyses carriedout using the simulation model: Estimation of the emission level of the voltage waveform asymmetry at the point of connection, estimation of the high harmonic components at the connection point and estimation of the emission level of long-term and shortterm flicker. Limits for the previously mentioned parameters have been defined in the National Grid Code (at the national level) or in the international standards. According to the international standards, the limit is considered violated if the duration of the parameter value violation exceeds 5% of the monitored period. Conventional approach of power quality analysis through software tool assumes only analysis for the most critical regime: when the short-circuit power at the point of connection is the lowest and the new power plant produces maximum active power. Based on this approach mitigation measures for improving power quality supply are sometimes suggested to the plant investor. In should be noted that Renewable Energy Sources (RES) do not have maximum output power during the whole year, and consequently, power quality deterioration is much less than in the critical regime observed in the simulations. For power quality simulation purposes, technical sheets of the equipment contain high harmonic levels for the full operation range are used from which usually the worst (highest) harmonic injections are considered for modelling RES as a harmonic source. In this paper, the results of power quality analyses for the RES connection using hourly resolution data for the one-year period based on DPL (DIgSILENT Programming Language) in DIgSILENT PowerFactory software package will be presented. This approach gives the duration of the limit violation, and consequently, more reliable results in comparison with the results of the conventional approach.