With the promise of improved efficiency and resiliency, and a reduced carbon footprint, the total capacity and spending on microgrids is projected to quintuple by 2028. From universities, hospitals, military bases, airports, and even single properties, microgrid projects range from complex retrofits of existing electrical infrastructure to modern greenfield designs. There is belief that we are in the midst of a reverse Copernican Revolution, where generation will be distributed away from the center to the grid’s edge. Microgrids will even import/export power from each other and help support the main grid. Electric utilities’ existing business models are under threat, and they have been forced to pay attention with some even seeing business opportunities.
By definition, a microgrid must be able to island itself and rely on its distributed energy resources (DERs). As the excellent feature article in June’s IEEE Power Electronics Magazine on AC microgrid control and management strategies notes, this “is not an easy task”, involving up to three levels of hierarchal control. At the “local” DER level, Primary Control is typically bundled per DER to maintain voltage and frequency stability, and reliability. Secondary Control, often associated with the microgrid controller, acts on the entire microgrid to manage deviations in voltage frequency and amplitude to ensure power quality and reliability.
HIL will be used to create cleaner vehicles and supply chains, and increase their levels of connectivity to renewable resources and infrastructure.
Tertiary Control covers power import/export to the main grid and to other microgrids. Both Secondary and Tertiary Control Levels can also be implemented using central or distributed approaches with the latter offering potential redundancy and cost benefit. While the Tertiary level is mainly used currently to optimize import/export economics based on electricity and energy markets, it can also serve to improve power quality in the higher-level system. All three control levels serve critical operational or economical functions within the microgrid and are connected relying upon digital communication. Furthermore, while AC microgrids are currently most common, full or partial DC configurations offer certain advantages and are gaining interest.