A reliable electricity grid is needed to support our daily needs. With the increased frequency of adverse weather in recent years, ensuring the resilience of the power distribution system (PDS) has become crucial. This is particularly important for critical services such as telecommunications, traffic control, and operations as well as for essential organizations such as hospitals during emergencies. However, our bulk electricity system is suffering from a lack of utility investment in an aging infrastructure and distributed resources in many areas. Microgrids with various types of distributed energy resources (DERs) have capabilities to enhance the PDS’s resiliency. Resiliency is defined as the ability of the system to keep supplying critical loads even during and after extreme contingencies.
The microgrid has been identified as a key component of the smart grid for improving power reliability and quality, increasing system energy efficiency, and providing the possibility of grid-independence to individual end-user sites. The U.S. Department of Energy (DOE) defines a microgrid as “a group of interconnected loads and distributed energy resources within clearly defined electrical boundaries that acts as a single controllable entity with respect to the grid. A microgrid can connect and disconnect from the grid to enable it to operate in both grid-connected and island-mode.”
According to this definition, a microgrid:
- Has distinct electrical boundaries.
- Can operate in grid-connected or island mode.
- Forms an independent, controllable entity.
- Comprises distributed generators and loads.
In 2018, California adopted a similar definition through its Public Utilities Code, (2018) Division 4.1, ch 4.5 s 8370 a (d). The definition states that a:
“Microgrid is an interconnected system of loads and energy resources, including distributed energy resources, energy storage, demand response tools, or other management, forecasting, and analytical tools that are appropriately sized to meet customer needs within a clearly defined electrical boundary that can act as a single, controllable entity, and can connect to, disconnect from, or run in parallel with, larger portions of the electrical grid, or can be managed and isolated to withstand larger disturbances and maintain electrical supply to connected critical infrastructure.”
DERs are increasingly integrated with the distribution network due to their ability to mitigate high marginal network losses, relieve network congestion, defer impending upgrades, enhance reliability, and improve resiliency. Therefore, DERs facilitate the formation of microgrids, which can operate in an islanded mode to support internal customers during outages, thereby improving the resiliency of the distribution grid as a whole. A microgrid is a self-sufficient energy system that serves the power needs of discrete establishments such as college/university campuses, data centers, hospital complexes, business centers, or neighborhoods. Within microgrids, various DERs such as solar panels, wind turbines, combined heat and power, generators, and battery energy storage systems (BESS), are used to generate power. A microgrid provides a unique set of capabilities, including the ability to serve critical loads that may shift in time, space, and size as well as the ability to meet loads for longer durations without a corresponding increase in fuel storage.
The microgrid represents a new paradigm for organizing the power system, enabling local integration of large amounts of renewable energy. One of the main advantages of microgrids is their ability to support and participate in electricity markets to reduce costs and provide strategies that generate revenue. Generally, microgrid controls are expected to meet these functional requirements:
- Present the microgrid to the utility grid as a single self-controlled entity to enable it to provide frequency control like a synchronous generator.
- Keep power flow within line ratings.
- Regulate voltage and frequency within acceptable limits during islanding.
- Maintain energy balance by dispatching resources.
- Seamlessly island and safely reconnect and resynchronize with the main grid.
Microgrid development and deployment are driven by three broad categories within the existing electrical grid infrastructure: Energy Security, Economic Benefits, and Clean Energy Integration. The ability of microgrids to improve the resilience and reliability of critical facilities, such as transportation, communications, drinking water and waste treatment, healthcare, food, and emergency response infrastructure has been the main driving force behind their development in the United States. In view of an aging infrastructure and frequent severe weather events, states have been exploring the feasibility of extending microgrids beyond critical facilities. Demonstration projects are being funded in this regard.
The rapidly declining prices of PV-Solar generation and BESS are making them increasingly competitive with traditional electric generation sources. The mass adoption of DERs and microgrids is poised to manage this transition by balancing supply and demand locally while ensuring reliability and resilience against natural and man-made disturbances. Whether microgrids remain a niche application or become abundant will depend on the degree of regulatory and policy support, the value they deliver in terms of power quality and reliability to property owners and communities, and the availability of control solutions that can maximize the benefits and return on investment (ROI) of microgrid projects.
The configuration and scale of microgrid services require monitoring, controlling, or load segmentation and will be based on the availability of energy from DERs. Depending on the configuration of grid-forming (GFM) or grid-following (GFL) inverters used at the site, custom programming expertise for plant-level power plant controllers (PPCs) is crucial and will drive the extent of benefits that can be reaped from the project. It is critical for optimal synchronization of the output of GFL IBRs to meet the POI requirements per the PPA to hit the desired ROI for the project. Similarly, more advanced custom PPC programming would be required for ensuring optimal, safe, and stable operation for GFM IBRs in a standalone microgrid arrangement or as part of a larger project.
With over 12 years of experience in control and network integration for renewable energy, including BESS, Nor-Cal Controls possesses the expertise to meet the custom control schemes required for different inverter-based resources (IBRs). We offer custom-built, non-proprietary on-site SCADA systems, including Historian, PPC, EMS/MPC, and MET station solutions for PV-Solar, PV-Solar + BESS, and BESS-only sites. Get in touch with us to discuss your existing or upcoming projects.
