The Department of Energy defines a (grid-tied) microgrid as “a group of interconnected customer loads and distributed energy resources (DER) within clearly defined electrical boundaries that acts as a single controllable entity that can connect and disconnect from the grid (known as “islanding”). Sustainable Power Systems designs microgrid consisting of wind and/or solar photovoltaic generation, load controls, energy storage, and dispatchable generators.
For additional information on why distributed microgrids are an important part of our energy future, have a look at this article published on GreenBiz.com: 10 Reasons Microgrids Matter to Corporate Sustainability