Simulation Optimizes Performance” Before the Power is Ever Turned On
By Bill Murch, Bruce Campbell and Jim Dankowski, Eaton
Major natural disasters, as well as cyberthreats, in the last few years have made it more difficult than ever for utilities to keep power flowing reliably. Traditional standby generators designed to support hours of power interruption are no longer adequate. As encountered in 2012 with Hurricane Sandy and recently in 2017 with Hurricanes Harvey, Irma and Maria, power outages impacted large numbers of customers for weeks and even months. A few areas powered by microgrids, however, kept the lights on.
Microgrids provide a platform to keep power on and critical assets operating over prolonged periods of time while isolated from a damaged or failed grid. The U.S. Department of Energy microgrid exchange group defines a microgrid as “a group of interconnected loads and distributed energy resources (DER) within clearly defined electrical boundaries that act as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid, enabling it to operate in both grid-connected or islanded mode.”
Microgrids can generally better manage distributed power generation by providing optimal control and dynamic stability, and by balancing demand and generation on a small but critical scale.
Grid resiliency and grid reliability are often used interchangeably, but the two terms are different. Power resiliency is the ability to sustain power during an adverse event and recover quickly if an outage does occur. Power reliability is the ability to consistently deliver electricity in the quantity and with the quality expected by customers. Both are critical to a host of industries and businesses. Power reliability is one of utilities’ primary missions and they are typically cautious to ensure that technologies are proven and tested before they’re implemented to ensure customer power is not adversely impacted. Power resiliency also is important to government facilities, research centers, financial institutions, industrial processes, data centers and a host of other organizations that can face dramatic costs due to even short-term power outages.
If the typical goal for microgrid projects is providing power resiliency, then customers must be assured that the system can perform as intended. Yet, there is typically not a one-size-fits-all solution. For each installation, many factors must be explored; including the existing electrical infrastructure, load profile and growth, utility rates, existing generation assets, generator control capabilities and more.
To ensure that a microgrid will perform as intended before implementation, the critical assets, such as police stations, hospitals, schools, emergency management facilities and others must be defined. In addition, because the electrical distribution system that provides resiliency via a microgrid will have its own unique application scenarios, it’s a good idea to fully develop and simulate a virtual microgrid for a specific application. This is a proven way to confirm that the system will perform as required, before making a significant investment. A virtual system, or digital twin, can also be valuable to simulate changes prior to implementation.
Microgrid Projects Advance
The drivers for microgrid systems have evolved and many industries already use the technology for several different applications. Installing a microgrid is no longer limited to research demonstration purposes or forward operating military bases. Microgrids can be easily applied to areas that already have access to solar, storage and other on-site generation sources.
Further, with increased capacity of solar, wind, energy storage, combined heat and power (CHP) and other DER, there is an opportunity to optimize energy to support resiliency to critical or essential areas and organizations. In addition, as technology and material costs for solar PV and energy storage have improved, it is now possible to generate reliable energy to improve system resiliency at competitive pricing levels.
Over the last decade, microgrids have become an increasingly compelling means to not only keep the power on, but to manage DER and system costs. In the U.S., microgrids are ideal solutions for several common installation scenarios:
“- Community microgrids that serve as refuge during a hurricane or other weather-related issues in disaster prone areas
“- High-resiliency areas for military and mission-critical areas
“- Rural and remote areas that currently operate on a weak grid
“- Areas where electricity is prohibitively expensive, like Hawaii
“- Upgrading the utility transmission and distribution system, where microgrids are relied on to provide the functionality of the grid that enables the deferment of more involved transmission and distribution system asset upgrades
In addition, with the increased penetration of DER, utilities increasingly want to keep renewable assets online and able to ride through events that may impact the grid.
SIMULATIONS REFINe/OPTIMIZE SYSTEMS, EVEN BEFORE GROUNDBREAKING
Because it seems like a microgrid should work, doesn’t mean it will work. Microgrid systems are typically complex and involve many interworking components, generating assets that might change over time and the electrical grid. As utilities and other organizations explore the use of microgrids for resiliency, demonstrating the system will work before ground is broken is crucial to ensure the basic functionality and purpose are achieved.
Developing a microgrid requires power system automation and control knowledge well beyond the specific energy resources and equipment involved. Seeing the big picture and understanding how to optimize the overall system are critical to microgrid success.
A simulation of individual microgrid components is insufficient and does not provide fundamental assurance of system performance or data beyond a small part of a complex system. It is, therefore, useful to leverage simulation software and experience. In utility applications, distribution system modeling has provided industry-tested critical modeling capabilities to better show the interdependency among system components, while providing more precise simulation of distribution systems and distributed energy generation resources.
A virtual microgrid provides insights on the feasibility, design and application in a virtual environment. Virtual microgrids, or hardware-in-the-loop simulations of complex microgrid systems, enable owners and project designers to understand the system as if the assets and devices were already connected. This demonstration informs how the system is configured and optimized during the design phase. The ability to play with the microgrid system before it is in place helps drive a better understanding of the system dynamics and feasibility—all based on data from the simulation. The virtual microgrid also gives owners confidence that the system will perform as expected, as well as data-driven insights to modify the design to optimize performance.
Often, the specific use cases and application requirements for a microgrid are fluid and depend on a multitude of factors, including grid conditions, user energy demand, renewable generation and more. Virtual microgrid simulation enables specific use cases to be demonstrated and allows data to be gathered from the results.
In addition, customer data can be imported into the virtual microgrid to help develop the system’s load profile and utility rate structures. From there, data can be exported from the virtual environment for further evaluation and measurement of performance metrics agreed upon in advance of the project breaking ground.
Accurate simulation results lead to more precise planning and management of the microgrid system, including distributed generation and DER. This allows projects to move quicker and more successfully, with confidence they are optimized from the beginning.
Insights from a virtual microgrid can be configured to specific requirements and application considerations. Insights also can enable pre-engineering and system configuration and optimization to save time (and money). The microgrid controller can be pre-configured and mapped based on the feasibility study and virtual microgrid simulation to help avoid project delays and save time during the installation and commissioning phase.
The controller is the next critical part of the system to examine. Its design can impact the microgrid and support evolving system requirements.
Supporting Smarter, More Resilient Power
As the electric grid becomes more complex, it is increasingly important that gird owners and operators make improvements allowing for smarter, more reliable bi- and multi-directional electricity flow that is responsive to the fluctuating consumption habits of utilities, businesses, residents and communities. This smarter grid will enable improved power resiliency.
If microgrid projects continue to meet analyst estimates, sellers and users of electricity will rely more on stored and renewable energy. As projects are planned, it is critical to understand how and if the system will work as intended.
Microgrid system simulation is a critical step in determining if the microgrid will work as intended.
Simulations are part of broader feasibility studies that attempt to answer whether a microgrid makes sense in a specific circumstance. If the answer is “yes,” feasibility studies and simulations can help ensure the overall system is optimally designed for a given scenario’s specific power needs.
Bill Murch is Eaton’s director of services, microgrid energy systems. Bruce Campbell is an engineering manager at Eaton. Jim Dankowski is Eaton’s government segment marketing manager.
Three Basic Operating Modes Typical for Microgrids:
1. Normal grid-connected operation: During normal operation, the microgrid is connected to the grid and the loads are powered by a mix of grid and distributed energy resource (DER) power. Local DER assets may be running behind the meter on the customer site.
2. Islanded operation: During islanded operation, the microgrid system is not connected to the grid and the load is powered by the DER independently.
3. Outage or black-start mode: Severe grid disruptions or loss of grid voltage with insufficient DER connected may result in a blackout condition. The microgrid must restart in an islanded mode via proper sequencing of DER and loads.