Microgrid Protection and Control

Microgrid performance categories outlines different performance categories of Distributed Energy Resources (DER), mainly focusing on their response to voltage variations and their capacity to withstand disturbances, also known as ride-through capabilities. The categories are split between normal performance (Category A and B) and abnormal performance (Category I, II, III).

Microgrid DER transformer configuration in Distributed Energy Resources (DER) significantly impacts microgrid operation. The typical YGND–Δ configuration can negatively affect protection schemes and cause overvoltages during faults, leading many U.S. utilities to prohibit it. A solution is to use a YGND–Y configuration, which maintains consistent fault currents regardless of DER size.

Other considerations of a Microgrid DER transformer requires a grounded electrostatic shield to control inverter noise, a sufficient K-factor for managing harmonics within temperature limits, and an appropriate MVA rating to accommodate inverter-based DERs and bidirectional power flow. Oversizing these transformers, as in a PV farm and a Battery Energy Storage System (BESS), helps prolong their lifespan.