Comparison of PV inverter controller configurations for CERTS microgrid applications

Microgrids are highly compatible with photovoltaic (PV) sources because of their ability to internally aggregate and balance multiple PV sources without imposing restrictions on the penetration of such intermittent power sources. There are two major types of inverter control configurations that are used in photovoltaic inverters to provide an interface to a CERTS microgrid. These control configurations exhibit important duality characteristics, and both are capable of tracking maximum input power while abiding by the CERTS droop algorithms. This paper investigates and demonstrates the comparative performance characteristics of these two major controller types: 1) a grid-forming droop-style controller similar to those used for controlling distributed generators; and 2) a current-regulated grid-follower controller. It is shown that only the grid-forming controller allows a PV source to operate alone in an islanded CERTS microgrid, but the grid-follower controller enjoys some inherent advantages with regard to faster dynamic response.