Toward Market-based Microgrid Control Systems: Inside Brunswick Landing

Kay Aikin of Introspective Systems describes the value of market-based microgrid control systems, as applied to an innovative project under development in Maine.

The largest machine on earth is often said to be our electrical grid. By the end of 2016 there were some 7,600 power plants greater than 1 MW and many smaller resources, as well as a myriad of control systems.

The grid is truly complex, made up of systems collected into ever larger systems. In the controls world this is called a systems of systems — the ultimate in complexity revealed in large systems like the electric grid and ecological systems.

Microgrids may help us tame the grid’s complexity by limiting the number of possible interactions that occur. Smaller more predictable systems are less prone to the kind of unintended consequences that led to the Northeast Blackout of 2003.

However, even microgrids will face greater complexity over time with the emergence of energy management systems and smart devices. This complexity can be used to build better systems. As ecologist Eric Berlow says, the more you “embrace complexity the better chance you have finding simple answers.” A great TED Talk illustrating this concept can be seen here.

It has been shown that market-based systems can be amazingly stable in complex environments because of the many naturally balancing feedback loops that emerge. This complexity can be used to lead to simplicity.

In the electrical engineering field, the GridWise Alliance has called this idea of market-based systems ‘transactive energy.’ Much of the research in this area has been done by the Pacific Northwest National Laboratory, including a successful trial known as the Olympia Peninsula Project (OPP), which demonstrated price signal-based control of distributed energy resources. The field project showed that market-based control was able to manage distribution constraints and reduce peak loads. This was followed by a Pacific Northwest Demonstration Project (PNDP) ending in 2015.

Three main methods exist for implementing transactive energy control systems applicable to microgrids:

  • Centralized (top down)
  • Centralized (auction-based)
  • Distributed (edge-based)

The difference between the Olympia Peninsula and Pacific Northwest Project was that OPP was
a double auction very similar to the current ISO systems. Meanwhile PNDP was a top down model
where demand response assets and distributed energy resources were optimally dispatched by
individual transactive nodes using two-way communications. Both were generally more
centralized paradigms.

The third transactive approach is a fully distributed edge control method that relies on pricing
signals reflecting the prediction of future conditions — which creates different prices at many different scales. Lower-level devices (or entire systems) respond to the pricing signals from higher levels. This method is currently being researched at Maine’s Brunswick Landing Microgrid Project for the Department of Energy.

The first two transactive energy approaches have shown promise in that they have been able to balance energy demand, lowering peak demand and managing grid congestion. But they rely on large two-way communication networks that are particularly vulnerable to cyber assaults.

This cyber vulnerability should be a concern to the microgrid community. As infrastructure experts have pointed out, if microgrids are to achieve widespread deployment, this communication vulnerability must be addressed.

The edge-based system being researched at Brunswick Landing uses an approach that minimizes this vulnerability. The system has pricing signals (potential of 10 or more different grid scales) that are continuously re-calculated. They only travel in a downward direction and are acted upon only by edge devices that have promise, using the “power of complexity to lead to simplicity.”

Since the scope of influence of a single node is typically only one or two degrees of separation (as described by Eric Berlow) this limits the computing power required to calculate the system state and provides for enhanced capabilities using advanced artificial intelligence techniques. Security risks are reduced with limited communications routes.

microgrid control

Midcoast Regional Redevelopment Authority (MRRA) systems map

Brunswick’s control system demonstrates, then, an effective transactive edge-based energy system that can provide increased resilience, versatility, reliability and flexibility. This approach can be used not only in microgrids but also for the greater electrical grid.

Kay Aikin is CEO of Introspective Systems, a complex systems architecture and engineering company in Portland, Maine. The project lead for the Brunswick Landing Microgrid Project, Introspective Systems is researching edge-based transactive energy networks.

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