Current Status and Issues of Concern for the Integration of Distributed Generation Into Electricity Networks

As existing distribution networks were designed to deliver unidirectional power to consumers and require minimal control intervention, they result in largely passive infrastructures. The installation of distributed generation (DG) units with significant capacity in these passive networks can cause reverse power flows, which will result in some conflicts with the operation of the existing protection system. In this context, utilities around the world have started establishing requirements to ensure safe and reliable interconnection of generators in low- and medium-voltage networks. The technical grid code requirements and regulations vary considerably from country to country. However, any standard should address the critical need to make the DG marketable by providing uniform criteria and requirements relevant to the performance, operation, and safety. This paper presents a critical review of the requirements adopted by distribution companies in selected countries, such as the U.S., the U.K., Germany, and Australia, to facilitate the connection of DG. The main problems, such as voltage regulation, islanding operation, and dynamic interactions among DG and loads, are discussed to identify a few points where attention is still needed to improve the reliability of distribution systems.