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Today’s electric power system is designed to deliver high-quality and highly reliable electricity to customers. A century of development has lead to massively interconnected system that brings power from central-station generators via transmission and distribution to end-use customers. Although this system has been providing relatively inexpensive power, issues remain such as increasing and volatile fuel costs, greenhouse gas emissions, meeting the mandated renewable portfolio standards, and increasing customer needs for higher reliability power. One potential solution to these issues is the use of strategically installed distributed and renewable energy sources integrated at the distribution level.
Distributed energy resources (DER) are sources of electric power that are not commonly connected to a bulk power transmission system, instead are interconnected near the load in the electric power distribution system. Typically, the individual DER unit ratings are less than 10MVA and include both fossil-fuel and renewable generation as well as energy storage technologies. Because DER are sited at customer load locations, they can be more efficient than central station generators because lower transmission and distribution system losses. Targeted deployment of DER can also relieve loads on a utility’s transmission, sub-transmission, and distribution systems, and effectively increase available T&D capacity and relieve undesirable congestions.
The wide variety of DER, however, also causes complexity when installed, applied and operated in electrical distribution systems. Traditional radial distribution systems are not designed for two-way power flow. Adding additional sources into distribution systems can affect system performance such as operations, protection, and system costs. Currently, no industry standard exists to determine the amount of DER that can be installed on a feeder without causing adverse effects.
In this paper, a novel methodology is developed that ranks utility feeders for implementation of DER systems. This is determined by calculating an index based on peak load reduction, increased system capacity, load-generation correlation, and feeder load growth. This value is also based in part on a statistical measure that quantifies the relationship between loads and the stochastic nature of renewable resources. This would allow the utility to gain insight into improved benefits from non-dispatchable renewable resources such as solar and wind technologies as well as dispatchable DER technologies.
Once the feeder that benefits the most from DER is identified, a second method is used to optimize the placement of the DER.Based on the screening methodology, it was found that feeders with a high peak load compared with the average load are good candidates for DER. For nondispatchable DER, it is important to have good correlation between the load and the DER output. The full methodology quantifies the factors that influence the performance and costs of the electrical distribution system and the characteristics of the DER. This work will be specifically useful to electric power utilities and end-use customers wanting to site DER systems.
|Selection of Distribution Feeders for Implementing Distributed and Renewable Energy Applications|