Bonneville Power Administration
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Transactive control signal at the heart of the project
Transactive control is the centerpiece of the demonstration project. Its success, combined with the testing of utility-level smart grid assets, will help make a business case for smart grid. That will allow utilities in the region to make wise smart grid investments and create a more robust power system for years to come. If successful, it also can serve as a model for national implementation.
The transactive control signals contain information about what power is available (and at what price) and what power is needed by end users. Two-way communication of this information - all the way from the source of electricity, such as dams or wind projects, to your home - allows intelligent devices and consumers to make smart energy use decisions thus bringing benefit to the region, to utilities and to consumers. These benefits include helping improve efficiency of the regions' power system, cost effectiveness, enhanced reliability and a smaller carbon footprint.
How does the transactive control signal work?
So what is the transactive control signal, exactly? The transactive control signal represents the monetary value of power in terms of dollars-per-megawatt-hour, at a given point in time and specific location, in an electronic form. The signal moves through the system (see graphic below), incentivizing the use and movement of power. It's a forward-looking signal, meaning that it forecasts days ahead and is updated every five minutes.
Data for the signal originates with the power generators. From there it propagates downstream through the network, following the flow of power, and corresponding to physical locations in the electrical system called nodes. These nodes can be anything (from appliances to a customer meter or a substation) that can receive information and transmit it, either up or downstream, so that other assets on the system can respond appropriately.
At each node, a decision is made to increase the incentive signal value if less electric load is needed below that point, or decrease the incentive signal value if more load is needed. Flowing in the other direction, starting with end-use points such as homes, information is accumulated and forwarded about expected energy use over the next day. In this way the transactive control system is a closed loop.
Generators see what the expected load will be and plan accordingly - end uses of electricity see what the expected price and availability will be and likewise plan their use. Over time, the incentive signal and the load signal converge, with planned supply of electricity matching planned use. In the figure on page 2, the incentive signal is shown as "operational objectives" and the load signal as "status and opportunities."
What are the benefits of the transactive control signal?
This two-way communication maximizes opportunities for the region to optimize the use of resources, such as renewable energy, and helps the system meet operational objectives, such as reliability. For example, if the wind is blowing and producing a lot of power in a particular locality or region, the transactive control system would make using that power locally a priority through pricing incentives.
Conversely, if a particular area were experiencing congestion on their transmission system, a feedback signal from the nodes would help move power to other parts of the system to help prevent a blackout.
Utilities can use the signal to optimize their own resources, including reducing peak load, reducing phase imbalance on a transformer or preventing overloads on a transmission line. Eventually the incentive signal will let consumers make educated choices about how and when to use electricity, and even at what price. Forty-one of the test cases in the demonstration project involve the transactive control signals.
Although the demonstration project will use simulated price incentives instead of actual changes in wholesale power prices, the structure of the project is intended to provide for a realistic scenario at a scale that can be applied regionally, and even to other parts of the nation. The transactive control system is slated to be up and running by September 2012.
The technical partners
Battelle's Pacific Northwest Division located in Richland, Wash., is leading the project. This non-profit organization is responsible for providing technical leadership, data management and overall project management. Battelle is responsible for the project's allocation and expenditures, schedule and quality control. They also are putting together the cyber security plan, in collaboration with the other partners.
The Bonneville Power Administration a federal agency in the U.S. Department of Energy, represents the project-level transmission, generation and renewable energy objectives of the region and will link the project together from the power system point of view. BPA has primary roles in business case development, outreach and external communications, system data input and design input.
Alstom Grid will define and calculate the simulated wholesale power price that will serve as the foundation for the transactive control signal. To that end, they will provide operations software, and provide services that will enable real-time dynamic pricing and renewable energy management in the project.
IBM is building the infrastructure to disseminate the signal and interlace it with the responsive assets. They are contributing servers and software that will allow for effective streaming of data.
Netezza's data storage appliance will provide processing speed and power to analyze and understand the project's data.
Quality Logic will develop tools to test the transactive control system's conformance to specifications and interoperability, and they will perform testing to confirm that the signals are correctly communicated along the nodal hierarchy. QualityLogic co-leads the investigation and adoption of national smart grid standards into the control signal. Testing and standards influencing efforts undertaken by QualityLogic and other project participants will help establish the nodal transactive control technology as a national standard.
3TIER will serve as the weatherman of the project, forecasting wind and solar resource availability at hourly intervals, days ahead and at five-minute intervals within the hour. These forecasts will affect the region's incentive signals to encourage variable renewable energy consumption when and where the resources are available.
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