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What Is Transactive Control? – How Distributed Transactive Control Works

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In the last installment, we discussed the state of the grid today and drivers that are making its current control architecture a dead end. Now we’ll discuss what’s happening now and what’s on the horizon.

How Does the “Distributed” Part of Transactive Control Work?

Just as in the Internet router architecture, the PNW-SGDP Transactive Control architecture distributes decision making throughout the network. Rather than having a single (or a few) central operations centers (like the online-service era characterized by companies like AOL, Compuserve, etc.), the Transactive Control architecture comprises nodes that could be deployed to make generation, transmission, distribution and load management decisions at hundreds, thousands and even millions of nodes (wherever generation, routing and power usage occur).

Each node in the Transactive Control architecture makes decisions based on local conditions and forecasts, its owner’s preferences, and conditions reported from “near neighbors” in the network – i.e., those nodes that either provide power to a node or consume power supplied by the node, or both. Inputs to these decisions include:

  • Local base power generation forecasts (including generation resources from traditional plants such as oil, hydro, etc.)
  • Local variable generation and storage forecasts (which may be variable and turned on/off easily based on variable forecasts and pricing information). Examples include Solar, Wind, local battery.
  • Local load and manageable (responsive) asset information and forecasts
  • Local energy cost forecasts
  • Multiple neighbor’s load, generation, and pricing information

All of the inputs above are collected and used to determine electric generation and usage decisions at each node. These decisions are then shared periodically in the form of both a load forecast and an economic forecasts of the value of electricity at the node over defined, short-term time intervals (in the case of PNW-SGDP, starting at five minute intervals, and forecasting as far out as three days).

Although the communication protocol definitions between nodes is standardized in this architecture, the decision making process for each node in this system is tailored to reflect the unique characteristics of the load and generation resources at that node. The decision making process can reflect pricing and regulatory policies, resource constraints, geographic considerations (pricing as delivered to that location), as well as specific manual interventions or automatic/algorithmic application of policies.

Transactive Control in Action

The Pacific Northwest Smart Grid Demonstration Project (a collaboration of 11 utilities, the Bonneville Power Administration, two universities and five technology partners) has implemented and is currently testing this architecture across five states and 60,000 metered customers as shown below. The project is funded by the American Recovery and Reconstruction Act and will conclude in 2014.

Figure 5 illustrates the top level nodes of the PNW-SGDP’s implementation of Transactive Control, covering the five-state geographic region involved in the project.

Figure 5. Top Level TC Nodes of the PNW-SGDP

Benefits of Transactive Control

The Transactive Control system provides a better representation of status and forecast within the regional grid than is achievable with traditional “centralized” or “top down” control models. As a result, the system as a whole will benefit because:

  • Generation and load (especially intermittent load) can be balanced more effectively, even down to a local level – helping preserve grid reliability.
  • Critical decision making can be accomplished in a highly parallel and redundant manner, reducing single points of failure as the managed grid continues to grow.
  • Consumers of power can access actual, real-time grid information and power values and optimize their power use and generation to accommodate their own preferences.
  • Pricing and load management decisions can be made based on an accurate forecast of the value of electricity as delivered to a specific location, accurately reflecting both grid-wide status and local conditions
  • Local decisions can be made quickly, in seconds (in the future) where necessary.
  • Policies and operational rules can be tailored to specific nodes.
  • New distributed generation resources and managed loads can be brought online and integrated into the grid more easily, with the impacts managed locally.

QualityLogic’s Role in Transactive Control

QualityLogic is the leader in Smart Grid software technology testing services, test tools, and software standards development. As a key partner in the PNW-SGDP, QualityLogic’s responsibilities include:

  • Performing functional, conformance and interoperability testing of the PNW’s transactive control system.
  • Providing interoperability guidelines to utilities to assist in purchasing and operating interoperable smart grid equipment.
  • Developing training programs to educate the participants in development of interoperable smart grid assets.
  • Contributing to the development of smart grid related standards in support of the PNW’s Transactive Control system.

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