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Optimal Power Flow Pursuit

National Renewable Energy Laboratory

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Technology Marketing Summary

The desire to improve grid resiliency and enable a sustainable capacity expansion has led to the growth of distributed energy resources (DERs) and the utilization of renewable energy sources. DER allows for smaller amounts of aggregate energy to meet the regular demand of the commercial, industrial, and domestic consumers. When combined with renewable energy sources, the distribution network supplying power is transformed into a smarter and more sustainable grid.

One major challenge in a distribution network is to optimally integrate DERs and renewable energy sources in large scale while congruently regulating voltages and ensuring that power-quality requirements are met. Feeders with high integration of photovoltaic systems give a prime example, given the increased likelihood of overvoltage conditions during solar peak hours. In this context, autonomous techniques currently tested for the distribution networks are Volts/VAR and Volts/Watt and may result in suboptimal system operation, with the former requiring the inverters to be oversized. On the other hand, centralized optimization approaches may not offer sufficiently fast decision-making capabilities. This is because in the time required to collect data from all of the nodes in the network, the underlying load, ambient, and network conditions may have changed.

Description

NREL researchers have developed distributed feedback controllers that continuously drive the power set points of inverter-interfaced devices to solutions of AC optimal power flow (OPF) problems. Accordingly, network-level performance metrics are achieved in real time while voltages are regulated within given limits. This is accomplished by leveraging online optimization techniques for the synthesis of the controllers. The controllers rely on instantaneous voltage measurements and do not require knowledge about the loads present in all feeder locations. These controllers can be implemented in microcontrollers that accompany interfaces of gateways and inverters. As a result, this controller that can pursue fast-changing OPF targets is beneficial and advantageous to those deploying traditional OPF and autonomous schemes because it is extremely adaptable and can result in better reliability and increased power quality. As an application, NREL researchers showed that the developed controllers enable an integration of photovoltaic systems well beyond current limits.

Benefits
  • Implementable onto micro-controllers and existing devices
  • High integration of DERs with reliability guarantees
  • Seek system-level performance objectives in real time
  • Real-time optimization
  • Enable inverter-based voltage regulation
  • Increased operational efficiency
  • Resilient to communication latency
Applications and Industries
  • Photovoltaic Systems
  • Grid Efficiency
  • Utility Industry
  • Micro-grid optimization
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
ROI 16-35DevelopmentAvailable06/14/201606/14/2016

Contact NREL About This Technology

To: Erin Beaumont<erin.beaumont@nrel.gov>