In a world where energy costs are increasing, power interruptions from extreme weather events are more frequent and the need to decarbonize is more and more important, microgrids provide an essential function. Microgrids deliver capabilities to help manage energy costs, enable more resilient operations and advance sustainability goals.
Most microgrids are connected to and operate in parallel with the utility grid so it’s important to understand what’s involved in grid interconnection. It’s critical to understand the impact these distributed energy resources (DERs) will have on both your energy system and the local grid. Getting ready to interconnect your microgrid with the local utility involves a lot of preparation to help avoid project delays.
Assessing impact — on your infrastructure and the grid
The interconnection process assesses the impact of your microgrid on the electrical safety, performance and stability of the local grid. The point of interconnection (POI) is also referred to as the point of common coupling (PCC). While the two terms can sometimes diverge in meaning, they are often used interchangeably. The details of this terminology can be found in the “IEEE 1547 Standard for Interconnection and Interoperability of Distributed Energy Resources with Associated Electric Power Systems Interfaces.”
It’s essential to prioritize safety, especially when working on projects that involve distributed energy resources operating in parallel with the larger grid. A brief primer on the National Electrical Code® 705 is a great place to start. This code addresses how to connect additional power production sources to the existing premises’ wiring system and operate in parallel with a primary source of electricity.
Because the electric grid is local, the interconnection process is largely localized as well, varying by state and utility. While there is no national standardization of the interconnection process, IEEE 1547 is the basis for many utilities’ interconnection requirements and provides general guidelines on what to expect.
While the specific grid interconnection requirements vary from utility to utility, the process for grid interconnection follows a similar path. Typically, an interconnection study is performed at the outset of the project to help determine the control, protection and capacity parameters required for compliant operation before a microgrid (or a large DER or load) is connected to the local utility.
The interconnection study will likely require a deep understanding of specific technologies such as inverter-based photovoltaics or synchronous generation. It also often includes steady-state and/or dynamic load flow, short circuit and coordination study, grounding review, dynamic simulation (e.g., transient stability study), electromagnetic transient simulation, and harmonics and flicker analysis.
To determine changes required behind-the-meter (to the building or campus), a microgrid feasibility study should also be conducted. During this process, you’ll determine if legacy automation and protection schemes need to be updated, replaced or augmented to accommodate the microgrid system.
Armed with data and insights from the grid interconnection and the microgrid feasibility studies, you and your utility can better understand possible equipment upgrades, grid impact, related costs and time required.
Planning through smart grid tools
Some states and utilities are making the interconnection process faster and simpler by requiring (or making publicly available) tools that help developers and energy consumers identify where and if new generation and load can be located. For example, the California Public Utilities Commission requires sharing granular data on DERs, such as electric vehicles, and grid load.
Essential tools such as Integration Capacity Analysis (ICA) or hosting capacity help automate aspects of the grid impact study and can significantly reduce the time and cost of integrating microgrids (and solar and storage) onto the grid. When available, ICA insights can dramatically improve the grid interconnection process.
Joe Williams is the distributed energy resources product manager at Eaton.
