Power Quality Assessment in Small Scale Renewable Energy Sources Supplying Distribution Systems

Nicolae Golovanov,Dario Zaninelli,George Lazaroiu,Mariacristina Roscia

doi:10.3390/en6020634

Abstract

The impact of wind turbines and photovoltaic systems on network operation and power quality (harmonics, and voltage fluctuations) is very important. The capability of the power system to absorb this perturbation is dependent on the fault level at the point of common coupling. The paper deals with power quality case studies conducted on existing renewable resources-based systems. Voltage fluctuations determined by a 0.65 MVA wind turbine are analyzed. The impact of photovoltaic systems on steady state voltage variations and current harmonics is investigated. The correlation between the generated power and the main power quality indices is highlighted.

Highlights

Renewable energy sources (RESs), with powers varying from 100 kW to a few MW, are increasingly present in electrical networks
K f ψ sc S r where N120 is the number of possible commutations in a 120 min interval, kf(ψsc) is the flicker factor defined for angle ψsc = arctan(Xsc/Rsc), Xsc is the reactance of short-circuit network impedance, Rsc is the resistance of short-circuit network impedance Sr is the rated power of the installation, and Ssc is the fault level at point of common coupling (PCC)
The voltage flicker study becomes necessary as the wind power penetration level increases quickly

Summary

Introduction

Renewable energy sources (RESs), with powers varying from 100 kW to a few MW, are increasingly present in electrical networks. The RES systems are “environmentally friendly” and appropriate for a large series of applications, such as stand-alone systems for isolated buildings or large interconnected networks The modularity of these systems make possible their expansion in the case of a subsequent load growth. The increasing penetration rate of RES in the power systems is raising technical problems, as voltage regulation, network protection coordination, loss of mains detection, and RES operation following disturbances on the distribution network [2]. These problems must be quickly solved in order to fully exploit the opportunities and benefits offered by the RES technologies.

Power Quality in Distributed Generation Systems

Steady State Voltage Variations

Current Harmonic Perturbations

Conclusions