Practical Aspects of Pre-engineering Design of Clustered Microgrids

Although microgrids are a popular research topic, design objectives of a real-life project are probably the largest uncertainty faced by planning engineers. Most real microgrid systems, i.e., those not built exclusively as a demonstration project, have as a primary goal increasing the reliability to be afforded to customers within the microgrid boundary, as well as resilience to ensure the microgrid can maintain its supply even for very long duration outages caused by high-impact-low-probability events. A secondary goal is oftentimes increasing the share of renewable energy produced and consumed by the microgrid loads, both under blue sky and black sky operation. As a result, the load serving capability of the microgrid operating under different fractions of renewable energy is another aspect of interest. Whether operating in blue sky or black sky mode, each microgrid operation must result in a stable state and the microgrid must maintain safe and reliable operation. These objectives apply to single microgrids as well as to networked (clustered) microgrids, where more than one microgrid form a cluster that can have each microgrid operating individually or a microgrid cluster operating as a networked system. Design aspects go beyond the planning phase, and consider designing the operation modes, the clustering approach, and impacts therein. Several aspects of power quality must be analysed to ensure design parameters are addressed. Only with this foundation, a clustered microgrid is expected to engage seamless transition and continue operating in both grid-tied as well as in off-grid condition uneventfully. Oftentimes this creates a focal point on protection and control. It is expected the microgrid can either have a single scheme that enables the dual operation mode, including transition, or to have practical means to quickly switch settings groups if the philosophy calls for more than one. This chapter provides an overview of several engineering aspects of two networked island microgrids.