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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
Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Date
Patent 10,148,092
Patent
10,148,092
Real time voltage regulation through gather and broadcast techniques
An example device includes a processor configured to receive a plurality of voltage measurements corresponding to nodes in a distribution network, and determine, for each respective node: a value of a first coefficient, based on a previous value of the first coefficient, a minimum voltage value for the node, and a voltage measurement that corresponds to the node, and a value of a second coefficient based on a previous value of the second coefficient, a maximum voltage value for the node, and the voltage measurement. The processor of the example device is also configured to cause an inverter-interfaced energy resource connected to the distribution network to modify its output power based on the value of the first coefficient for each node and the value of the second coefficient for each node.
12/04/2018
Issued
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>