CIRED Workshop - Lisbon 29-30 May 2012 Paper 0020 Paper No 020 Page 1 / 4 An Overview of the Present Grid Codes for Integration of Distributed Generation Traian-Nicolae PREDA Kjetil UHLEN Dag Eirik NORDGÅRD NTNU – Norway NTNU – Norway SINTEF Energi AS - Norway Traian.Preda@elkraft.ntnu.no Kjetil.Uhlen@ntnu.no Dag.Eirik.Nordgaard@sintef.no ABSTRACT Power systems are passing through profound changes, mainly due to the liberalization of electricity markets, the depletion of primary energy resources and the concern about climate change. The aforementioned premises have created a favorable frame for development of distributed energy resources. As a result, the level of integration of distributed generation (DG) technologies, especially in distribution networks has increased. In order to counteract the impact of DG on the stability and reliability of power systems, the transmission and distribution systems operators have started to reconsider and update their national grid codes. This paper provides an overview of the most recent and comprehensive grid codes regarding the DG integration at distribution level. 1. INTRODUCTION Grid codes are not new topics in the power systems literature. They started to appear more than 15 years ago, for transmission systems, as a set of technical guidelines and operation specifications which large conventional power plants needed to comply with. The grid codes differed from country to country due to the different regulations laws and different characteristics of their national power systems. At distribution power system (DPS) level, grid codes were mainly used to specify and design the guidelines which the distribution network operators (DNOs) will apply in the planning and development of DPSs, with the compliance of end users (loads). In today’s context, when generation had moved, also to lowest levels of the power systems (medium and low voltage levels), the loads have transformed from passive components into active ones and power systems into entities with a bidirectional energy and informational flow. When this change occurred in the DPS, the DNOs assessed normally the DG integration by conducting simple integration studies (load flow, basic power quality studies) because the amount of DG integration was small and the stipulated technical guidelines were simple or even absent [1]. Currently, when the worldwide share of DG is increasing, awareness grows in the concerns of network operators for the need to revise and upgrade the DG connection guidelines, in order to achieve a stable and proper operation of the overall power systems. In the last years, a harmonization work of grid codes related to DG has been carried out at international level and the results are being shaped into a set of standards and recommendations. Most of them have become part of the national policies regarding DG or reference points for developing new ones (e.g.: IEEE-1547, IEC-62109, IEC- 62477, ENTSO-E draft grid code). This paper will give an overview of the grid codes elaborated at DPS level regarding: frequency and voltage operation areas, active and reactive power control, voltage grid support during balanced disturbances and reactive current injection or absorption. The surveyed grid codes are from countries which faces large amount of DG integration, like Canada (Hydro-Québec, Manitoba Hydro), Denmark, Germany, Ireland, Norway, Spain and United Kingdom. Also the draft grid code of the ENTSO-E and IEEE Standard 1547 will be investigated. 2. COMMON REQUIREMENTS FOR GRID CODES RELATED TO DG In this paper the following set of common technical connection requirements will be surveyed, based on the operation states in which a DPS can be found: a) Steady state operation: - Frequency and voltage ranges - Active power output control - Reactive power output control b) Dynamic operation during grid disturbances: - Grid voltage support during disturbances - Reactive current injection or absorption for fast acting voltage control - Synthetic inertial capability or inertia emulation - Oscillations damping in DPS The grid codes reviewed are listed in the Table I. Table I. Grid codes related to DG reviewed in paper Country Grid Codes related to DG Canada Hydro- Québec (February 2009)  Requirements for the Interconnection o istrited eneration to the ydro- ec edim-oltage istrition ystem  2] Manitoba Hydro (January 2003)  Interconnection Guideline or onnecting istrited esorces to the anitoa ydro istrition ystem  3] Denmark (October 2008)  Technical Regulation for Thermal Power tation nits larger than   and smaller than .  4] Germany (June 2008)  Guideline for generating plants’ connection to and parallel operation with the medim- voltage networ  5] Ireland (March 2011)  irrid rid ode  6] Norway (October 2006)  Tekniske retningslinjer for tilknytning av produksjons-enheter, med maksimum activ effektproduksjon mindre enn 10 MW, til distribusjonsnettet  [7] Spain (October 2008)  Technical requirements for wind power and photovoltaic installations and any generating facilities whose technology does not consist on a synchronous generator directly connected to the grid  8] United Kingdom (June 2009)  he rid ode  9]  he istrition ode  10]