Introduction

Dispersed generation (DG) is attracting more attention from electric power producers and consumers as an alternative for electric capacity and energy supply. Deregulation, increasing energy demand, and economic, environmental, and political barriers to developing new bulk generation and delivery infrastructure are all contributing to this emphasis on DG. Wind generation has already emerged as an option for utility-scale generation, as evidenced by the growing number of commercial projects worldwide and increasingly favorable and competitive economics. Although wind is considered primarily as a bulk generation resource, a growing number of installations are being deployed on distribution systems at or near smaller load centers.

Because most distribution systems in the U. S. have been designed to operate as radial systems, the installation of DG in significant amounts can result in some conflicts with distribution operations. These possible conflicts, coupled with the recent renewed interested in distributed generation sources, has prompted a great deal of interest in DG interconnection practices within the industry. IEEE 1547 is the DG interconnection standard developed through the combined efforts and support of the U.S. Department of Energy, NREL, electric utilities, DG hardware technology manufacturers, and consultants.

This standard establishes criteria and requirements for interconnection of DG to the electric grid. The guidelines in this standard apply to all distributed generation sources, including distributed wind generation. Wind power as a DG resource receives more scrutiny than more conventional distributed generation technologies because of its intermittent nature. In addition to the typical DG interconnection issues, wind generation results in an increased potential for power quality-related problems such as voltage flicker and voltage regulation issues. Deeper understanding of these possible interconnection issues is vital to wind generation being considered as a viable DG solution.

Distributed generation and, more specifically, distributed generation with wind turbines, falls outside the body of conventional power system engineering practice. "Rules of thumb" that have stood the test of time for power system planning, design, and operation, along with the analytical tools and techniques upon which they are based, may no longer be valid or applicable to distribution feeders which interconnect with these unique generating resources. Without adequate precaution and design, DG has the potential to degrade system reliability, functionality of protection systems, and safety. Many states and organizations are developing requirements and guidelines for connection of DG to electric distribution systems. While such guidance will certainly be helpful to utility engineers, each prospective DG installation must still be evaluated in the planning and design stages to determine specific impacts on distribution operations and to understand the expected benefits. These evaluations will require new tools that combine consideration of the unique characteristics of wind generation with power system analysis techniques.

Because many of the high wind resource areas are primarily rural, most existing and planned distributed wind turbines are connected to smaller utility distribution networks. These utilities often have fewer resources to analyze the potential impacts of wind generation on their systems. Their distribution engineers often perform many different functions and have limited time to investigate, interpret and apply relevant industry and regulatory guidelines. These engineers need associated evaluation tools that are easy to use, require minimal input data manipulation, and integrate with existing data formats to the extent possible.