Microgrids, microgrids, microgrids: A holistic overview

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Juan Matson, senior sales manager, Gas Power Systems North America at Rolls Royce, explores how microgrid controllers can maximize the benefits of DERs.

microgrid controllers

Juan Matson, senior sales manager, Rolls Royce Gas Power Systems North America

A key value proposition for microgrids is that they put into context the old and the new. Microgrids are a new way of looking at the old energy and power problems from quality, reliability, availability, stability, adequacy and efficiency standpoints. Microgrids bring power sources closer to the consumer, therefore intrinsically increasing the reliability, efficiency and availability of the power provided.

As outlined in FERC Order No. 2222, microgrids also offer new enabling streams such as the ability to participate in grid services and support, as well as other models like arbitrage, mid-merit, spinning reserve, peak shaving, inertia, voltage and frequency regulation, efficiency and performance agreements, and operating reserves and deferrals.

Finally, microgrids present an opportunity to repower existing plants with more reliable and efficient technologies.

Much has been written about microgrids and it’s such a complex topic, so you might wonder if you can actually benefit from a microgrid. There is no doubt that the answer is yes, so long as the foundation of its individual components is strong.

Foundational elements: Electric codes and standards

Knowing how your microgrid will be used will define the course of its design. It’s also key to understand which distributed energy resources (DERs) will be at play. A microgrid puts all the DER elements and electrical distribution components into a common strategy to provide one customer end goal — that they get their power with the flip of a switch.

Based on the end use and the distributed energy resources, we use electrical codes and standards to better design microgrid systems. For example, the design should consider certain codes and standards set forth by the National Fire Protection Association (NFPA). Some applicable codes could include the National Electric Code (“NEC” or NFPA 70), NFPA 99 (for healthcare facilities), or NFPA 855 (for energy storage systems). Other codes relevant to renewables, emergency backup power, critical operation power systems and DC microgrids may also apply, as might the Institute of Electrical and Electronic Engineer’s Standard P1547 for grid-interaction and interconnection. Local or regional grid codes are also a key factor in a microgrid’s design.

Foundational elements: Microgrid controllers

As noted above, microgrids bring a variety of energy sources (DERs) together into something that serves the intended purpose of a given customer or end user. The microgrid controller is a key component from this DER management point of view because it provides the necessary interface for real time control of different energy sources that are managed by different rationale scenarios. For example, the microgrid controller must account for best levelized cost of electricity (LCOE) and it must manage power switching and protective devices, as well as the loads and the grid feeders that are tying into the system.

The controller is also charged with the task of defining, based on the grid’s suitability, whether the microgrid’s mode or sequence of operation is on-grid or off-grid. Thus, the controller is actively synchronizing and re-synchronizing the different assets, sharing active and reactive powers, and providing the necessary protective functions to run them safely.

A microgrid controller could be tasked with the following from the DER management perspective:

  • To minimize and optimize the use of genset running hours while maximizing their load factor to rationalize the time before overhaul expectation.
  • To avoid the curtailment of renewable energy, maximizing its contribution and improving its integration into the system, while maintaining power production and stability.
  • To maximize the usable capacity of an energy storage system (ESS) by means of optimizing its state of charge while securing its intended purpose (managing frequency or voltage imbalances, trading, arbitrage, or peak-shaving, among others) and its cycling expectations until its end of life.

Controlling the above can be done under scheduled or fixed operation principles signaled by DER availability and LCOE. The controller can define the load best add/shed strategies to maintain stability while securing maximum availability, as well as provide a comprehensive and intuitive user experience through human machine interface and cloud interfacing for data acquisition, visualization, reporting and analyzing.

These controls can also be layered for primary, secondary and tertiary functionality. This provides better coordination in multi-microgrid systems and enables voltage and frequency stability to be maintained, power to be shared and circulating currents within the microgrids to be mitigated. It also allows for voltage and frequency restoration within systems and optimization of the overall energy management and operation.

One control system can satisfy the requirements of these layers depending on the size and number of assets/systems involved.

Building on a strong foundation

All the aforementioned enable microgrids to be the foundation for new energy transition schemes such as Power-to-X. Power-to-X brings more flexibility to the complexity of variable renewable energy dispatchability such as hydrogen or synthetic fuels (liquid or gaseous).

As I consider the benefits of microgrids, I think about four questions: What do I want to accomplish? How will I accomplish it? Which components/technologies should I use? And what can I do to better rationalize and compartmentalize my existing demand to optimize the solution and even make it more bankable and profitable?

All-in-all the microgrid solution is an important shining star in the energy transition’s bright future.

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