Distribution Integration
The goal of NREL's distribution integration research is to tackle the challenges facing the widespread integration of distributed energy resources while maintaining the safe, efficient, and costeffective operation of the distribution system.
NREL's research on the integration of distributed energy resources, such as PV, began more than a decade ago and has included numerous highimpact projects. These projects have spanned the research spectrum from comprehensive projects in which we partnered with utilities to develop best practices for solar integration, to developing technical screening methods to “fast track” the interconnection of distributed energy resources, to evaluating the value of energy storage systems in the distribution system.
Capabilities

Modeling of advanced distribution systems, including quasistatic timeseries models, planningtype models, distribution dynamic models, and advanced distribution system equipment models

Modeling of microgrid systems

Development of advanced distributed energy resources interconnection technical screens

Modeling of aggregated distributed energy resource impact on the bulk system and verification with distributionlevel phasor measurement unit data

Evaluation of new distributionlevel grid technologies

Detailed analysis of distributed energy resource system costs, capabilities, and implemented use
Projects
This project addresses the use of high penetrations of PV in islanded microgrids to increase overall system efficiency, decrease fuel costs, and maintain resiliency of the overall system. A real microgrid scenario with a high penetration of PV is being tested in NREL's Energy Systems Integration Facility. Multiple control cases for firming PV using storage tested.
In this project, NREL is providing research and testing support to San Diego Gas & Electric, including:
 Energy storage sizing and placement
 Integrated Test Facility development
 Realtime digital simulator modeling and simulation
 Visualization and virtual connection to NREL's Energy Systems Integration Facility
 Microgrid simulation and testing areas.
This project developed utilityrelevant insights for the interconnection of high penetrations of distributionconnected PV systems. Efforts focused on:
 Developing distribution system modeling methods to determine the impact of high penetrations of distributionconnected PV on the local distribution system
 Making advances in how the variability of PV is modeled in quasistatic timeseries simulations
 Performing field measurementbased validation of PV impacts on actual test circuits
 Laboratory testing of advanced PV inverter functionality
 Performing a field demonstration of advanced inverters' ability to mitigate PVrelated impacts in highpenetration scenarios.
The capstone of the project was the development of an effective quickstart guide and reference for utility engineers working on distributed PV interconnection.
The Microgrid Cost Study is focused on identifying the costs of components, integration, and installation of existing U.S. microgrids and project cost improvements and technical accelerators over the next five years and beyond. This information can be used to develop research and development agendas for nextgeneration microgrids that provide costeffective, reliable, and clean energy solutions. This project will provide insight, transparency, and standardization in the reporting of microgrid costs and identify market segment differences for future cost reductions across microgrid applications
Quasistatic timeseries (QSTS) analysis of the distribution system is valuable when studying the anticipated impacts of interconnecting new PV systems. As the number of PV systems on distribution systems increases, the application of relatively simple, conservative assumptions or proxies for anticipated PV impacts becomes ever more unrealistic and potentially limits the amount of PV allowed to interconnect. However, the data and time required to complete QSTS analysis are formidable barriers to its everyday use in utilityrelevant PV interconnection studies. This project seeks to eliminate these barriers by decreasing the time required to complete a yearlong 1secondresolution QSTS study from 50 hours to 5 minutes and developing load and PV models that are easy to use with existing lowerresolution utility and environmental data.
NREL's PREconfiguring and Controlling Inverter SEtpoints (PRECISE™) tool is a standalone system that enables autonomous operation of distributed energy resources by leveraging advanced inverters modes. Developed in partnership with Sacramento Municipal Utility District, PRECISE helps utilities in the United States and beyond by identifying optimal inverter modes and settings to maximize the costeffective use of installed solar systems. The PRECISE platform has a quasistatic time series capability, combined with mathematical optimization, and three modules that operate in a specific order to identify optimal advanced inverter modes. The distribution powerflow module provides distribution operators an interface to view the network topology, geographical location of the requested PV system, and other existing PV systems.
Publications
On the Path to SunShot: Emerging Issues and Challenges in Integrating Solar with the Distribution SystemPDF, NREL Technical Report (2016)
HighPenetration PV Integration Handbook for Distribution EngineersPDF, NREL Technical Report (2015)
In Divergence There is Strength: Measuring and Mitigating Solar PV Impacts in Southern California Using Power Factors Other Than One, IEEE Power and Energy Magazine (2015)
Field Demonstration of Using Advanced PV Inverter Functionality To Mitigate the Impacts of HighPenetration PV Grid Integration on the Distribution System, IEEE Photovoltaic Specialist Conference (2015)