Control and Coordination in a Transactive Energy Environment

JEFFREY D. TAFT, PHDCHIEF ARCHITECT FOR ELECTRIC GRID TRANSFORMATION

JAKOB STOUSTRUP, PHD

CHIEF SCIENTIST / ADVANCED CONTROLS PROGRAM MANAGER

PACIFIC NORTHWEST NATIONAL LABORATORY28 MARCH 2014

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Our Grids Are Changing

• Generation is dispatchable• No significant energy storage in the grid• Power must be kept in balance• Generation follows load• Distribution “floats” on transmission

• Designed/operated for reliability, not economy

We are in the process of

violating these principles!

Now we want to operate pervasively for joint economic/control optimization in this newer highly complex environment with potentially millions of interactive endpoints.

Emerging Trends for US UtilitiesIntegration of renewable sources at T and D levelsReduction of grid rotational inertiaInteractive loads/prosumers/expanded marketsTime scale shift (to faster grid behaviors)T&D level power electronics penetrationDG/DR penetration and local energy networks (microgrids)

30%

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New(er) Grid Functions• VER integration (wind, solar, etc.)• Wide area measurement, protection, and closed loop control• DER/DG integration (distribution level)• Energy storage integration• Responsive loads (command, price, and /or system frequency)• Integrated Volt/VAr control (LTC/cap)• Advanced distribution fault isolation/service restoration• Third party energy services integration• Grid stabilization (H reduction)

• Electric Vehicle (EV) charge management• Inverter control for fast VAr regulation• Local energy network and microgrid power balance, load sharing and flow control• Multi-tier virtual power plants• Energy/power market interactions for prosumers; Transactive Energy• Electronic grid stabilization (FACTS for transmission; DSTATCOM for distribution)• Load modulation of buildings, electric

vehicle chargers, and data centers for local balancing

No single use case predominates; the control approach must support ensembles of new functions; utilities are being driven to select their unique function sets.

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Issue: Grid Coupling/Feedback• Electrical physics rules the grid – shaped by grid

connectivity

• Business models and software cannot change this

• Must be taken into account in control design to avoid unintended consequences

IVVR/DR*

• Becomes important as new rollouts of smart devices scale to full deployment

• Implications for architecture, design, and control

*Jose Medina, Nelson Muller, and Ilya Roytelman, Demand Response and Distribution Grid Operations: Opportunities and Challenges, IEEE Trans. On Smart Grid, vol. 1, pp. 193-198, Sept. 2010.

CVR/PV Market/responsive loads

Issue: The Coordination Problem

Power grids do not have a strong multi-tier coordination frameworko Power grids are inherently tiered nowo QSE’s-> Bulk System-> DSO’s->End Userso Distribution “floats” on transmissionDER as a “threat” and an opportunityA proper coordination mechanism is key to enabling new business modelsInterop standards alone do not solve this issue

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Systemic Issues/RequirementsThe most obvious: o Reliability/scalabilityo Stabilityo Security

Less obvious:o Federation/constraint fusiono Disaggregationo Boundary deferenceo Local “selfish” optimization (organizational autonomy)o Communications compatibility scalar control

In fact, there are about 80 “-ity” type characteristics that everyone quotes*

*John Doyle and John G Brown, Caltech, Universal Laws and Architecture. Available online as 1_DoyleSageLec1_May7_2012.pdf

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Wide Area Scalar Control Approaches

Solve the communications and disaggregation issues simultaneously and scalably (maybe!)Send scalar signals to endpointso Global common signal broadcasto Location-dependent values

Various Approacheso Distribution-Locational Marginal Pricingo Transactive Energyo “Prices to Devices”

Embedded Markets and Prices to Devices

Embedded market and prices-to-devices models

Scalar signal disaggregation models

Scalability

Instability

Directionally good but still lackingcoordination capability, so needs a better foundation/framework

Roozbehani, M., et al, Volatility of Power Grids under Real-Time Pricing, MIT, 2011, available online

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Transactive Energy

Definition from GridWise Architecture Council“The term “transactive energy” is used here to refer to techniques for managing the generation, consumption or flow of electric power within an electric power system through the use of economic or market based constructs while considering grid reliability constraints. The term “transactive” comes from considering that decisions are made based on a value. These decisions may be analogous to or literally economic transactions.”

Key elements:• Decisions (and control) based on value • Reliability constraints

Network Utility Maximization: Layering for Optimization Decomposition

Combine ideas from Control Engineering and Networking Multi-tier control coordination Benefits from layered architectural paradigm

Mung Chiang, Steven Low, et. al., Layering as Optimization Decomposition: A Mathematical Theory of Network Architectures, Proceedings of the IEEE, Vol. 95, No. 1, January 2007.

LAMINAR COORDINATION

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Coordination: Essential Structure Matches the “clean” layered model for the grid hierarchyProvides scalable coordination while respecting organizational and system boundariesConsistent with solid architectural principlesLaminar coordinators* can incorporate TE nodeso Replaces ad hoc TE node

approach with uniform control architecture for joint economic-control optimization

*J. Taft and P. De Martini, Scalability, Resilience, and Complexity Management in Laminar Control of Ultra-Large Scale Systems, available online.

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Transactive Energy and Laminar FrameworkBy adding the Laminar Coordination concept to TE, can we address the issues listed earlier?Decomposition allows mapping to real systemsFormulations provide constraint fusion and local goals

ISO

Gen TO

DSO DSO DSO

StorageController Substation Substation

PV Panel

Customer Device

Cap BankController

Master Problem

Sub-problemSub-problem

Secondaryproblem

SecondaryProblem

Secondaryproblem

Sub-problemTertiaryProblem

Tertiary Problem

Sub-problem

Sub-problem

Sub-problem

Sub-problem

Local Area Grid Local Area Grid

Physical Power System Layered Optimization Mapping

IVVC

EVCharging

PV DG

B2G/DR

ISO

Bulk Storage SubstationSubstation

Generation

DSO DSO DSO

TO

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Make It a Platform and They Will Innovate

We cannot predict all the new business models and applications that may emerge:o Local energy balance via B2Go Third party ancillary serviceso Feeder stabilization/regulation services via smart inverterso Utility-owned, customer-sited DERo Customer-owned, utility-managed DERo Multi-microgrid managemento DSO as DER coordinator

But, we can position the grid as platform and the DSO as an energy business hub if the control architecture is done properly

thank you

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Jeffrey D. Taft

jeffrey.taft@pnnl.gov

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resource slides

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Issues with Prices to Devices

• Hidden feedback, flash crashes, lack of tools to ensure stability leads to price and grid instability

• Multiple prices for the same kW-hr to a single end used from separate parties/processes; price-overwriting at the endpoint

• Differing prices to different endpoints for what is an apparently

equivalent kW-hr• Time scale mismatch between necessary control actions and

market functions• Presumed over-disaggregation (cannot really have individual

components of a system, say in a factory, responding differently to prices, so cannot disaggregate to individual devices)

Embedded Markets/Prices to DevicesEmbedded market approaches may act as a control elements in a feedback control loops, whether intended or not.

Hidden feedback, flash crashes, lack of tools to ensure stability -> price and grid instabilityMultiple prices for the same kW-hr to a single end used from separate parties/processes; price-overwriting at the endpointDiffering prices to different endpoints for what is apparently equivalent kW-hr (due to D-LMP or non-system, i.e. very local, markets)Time scale mismatch between necessary control actions and market functionsPresumed over-disaggregation (cannot really have individual components of a system, say in a factory, responding differently to prices, so cannot disaggregate to this level)

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Value Representation in TE

Value might be represented in a traditional currency form (dollars and cents)o Advantage: easily understandable

More generally, signals do not have to be currency to be economic or value-basedNot all values are necessarily converted to $o Economic signals do not have to be currency – behavior and math are

determining factors o Dual decomposition uses abstract price signals for coordination, for

example*

Want to enable value unlocking in general, regardless of business model or market structure

* Alternative Distributed Algorithms for Network Utility Maximization: Framework and Applications , Daniel P. Palomar and Mung Chiang, IEEE Trans. Automatic Control, Vol. 52, No. 12, December 2007.

Issue: Emerging Lines of Grid Control

EmergingArchitectural

Chaos!