INTEGRATION OF PHOTOVOLTAIC POWER SYSTEMS IN HIGH-PENETRATION CLUSTERS FOR DISTRIBUTION NETWORKS AND MINI-GRIDS

 ABSTRACT 

This paper presents the results to date on international experience and measurement campaigns on power quality analyses and the examination of grid stability of electric networks with high penetration of photovoltaic (PV) generation. Field data from participating International Energy Agency (IEA) member countries that are part of R&D collaboration within the IEA Photovoltaic Power Systems (PVPS) implementing agreement are reviewed. Inherent characteristics and network configurations employed worldwide in several grid-connected PV clusters and autonomous PV mini-grids developments are discussed and major observations on power quality impacts are summarized. The focus of the paper is to summarize information on the current knowledge and previous experiments with these systems to identify areas for further investigation and technology enhancement that enable development of high penetration PV networks. In addition, the results from voltage analysis case studies are presented. The studies consider effects of design practices and location selection on rate of change of the voltage caused by load and generation variations in the PV cluster. This supports the work plan of the new IEA PVPS Task group 11 on PV-hybrid systems within mini-grids. 

SOMMAIRE 

Cet article présente les résultats obtenus à ce jour dans le cadre d’expériences internationales portant sur des analyses de la qualité d’onde et de la stabilité des réseaux électriques dans un contexte de haute pénétration de systèmes photovoltaïques sur le réseau de distribution. En particulier, nous avons fait une revue de données recueillies par les membres participant au programme sur les systèmes photovoltaïque (PVPS) de l'Agence international de l’énergie (AIE). Les caractéristiques et configurations des réseaux typiquement utilisés dans de nombreux systèmes PV regroupés ou en mini-réseau autonome sont rapportées et mises en contexte. Le but de cette revue est de faire un sommaire des résultats obtenus à ce jour et d’identifier de nouvelles pistes qui méritent d’être étudiées davantage. De plus, on y présente les résultats d’études de cas sur l’analyse de la tension. Ces études considèrent les effets des pratiques de conception et du choix de l’emplacement sur le taux de changement de la tension causé pas les variations de charge et de génération à l’intérieur d’un secteur comportant une haute concentration de systèmes PV. Cette étude fait partie intégrante du nouveau plan du groupe de travail 11 de l’AIE PVPS qui étudie les systèmes hybrides photovoltaïques dans les mini-réseaux. 

1. INTRODUCTION 

The installed capacity of photovoltaic (PV) generation sources in grid-connected applications in countries participating in the International Energy Agency (IEA) implementation agreement on Photovoltaic Power Systems (PVPS) exceeded 2000 MW in 2005 [1]. Rooftop mounted PV installation on residential houses and building-integrated PV installation for commercial customers are supported by incentives in many countries. 

The experience gained integrating PV into the distribution grid can provide useful guidelines for the integration of other distributed energy resource (DER) technologies in the future. 

The IEA PVPS is one of the collaborative research and development (R&D) implementing agreements within the IEA. It is mainly focused on conducting joint projects in the application of photovoltaic energy conversion systems and investigation of technical/non-technical operating issues of PV systems. The PVPS program has been a pioneer in studying the impact of high penetration levels of PV on the distribution network. Some of the previous projects and collaborative studies that considered high penetration of PV systems are: impact study of increase in power penetration for grid-connected PV systems on voltage profile of the networks [2], probability assessment of islanding occurrence in the grid-connected low voltage networks [3], and analysis of the risk involved in islanding of low voltage networks [4]. 

The recently established IEA PVPS Task 11 working group aims to undertake research and studies on the issues involved in design, control, and implementation of PV hybrid systems within mini-grids, [5]. The mini-grids may operate autonomously (e.g. rural electrification applications), or may interconnect with the utility grid, but have the ability to isolate and operate autonomously. Since PV penetration in mini-grids may be quite high, particularly a significant portion of the load is assumed to be supplied by PV when operating autonomously, Task 11 is interested in the power quality effects of high penetration and the planning and design requirements to mitigate these effects. Table 1 shows the proposed scope of the IEA PVPS Task 11, [5]. Neither the PV cluster nor the remote community mini-grid completely represents the mini-grid of the future, which will operate in both autonomous and utility interconnected modes to supply multiple users. However, experimental knowledge and field demonstration cases for mini-grid systems that operate in both autonomous and utility interconnected mode are very limited. Hence, the study and identification of common operating problems for PV clusters and existing remote mini-grids can build the knowledge-base for the PV mini-grids of the future. 

 Farid Katiraei¹, Konrad Mauch², Lisa Dignard-Bailey¹ 

1. CANMET Energy Technology Center-Varennes 

1615 Lionel-Boulet Blvd., P.O. Box 4800, 

Varennes, QC, Canada, J3X 1S6 

*E-mail: farid.katiraei@nrcan.gc.ca 2. KM Technical Services  Vancouver, BC,  Canada  E-mail: konrad.mauch@ieee.org

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