Autonomous power electronic interfaces between microgrids

The use of back-to-back (BTB) voltage source converters (VSCs) to interface large scale asynchronous ac power systems is well established. BTB VSCs also provide a convenient means to interface small scale microgrids and the utility power grid. The relatively small size of such interfaces and broad scale of their application would mandate autonomous fast operation based on the health of the microgrids, although their preferred operating points (set-points) may be dispatched from relatively slow supervisory systems. This paper presents a method to control such interfaces so as to preserve microgrid-like operation of each ac system and to autonomously transfer power across the interfaces. The paper describes the control architecture, analytical model, and design method that ensure robust operation. We demonstrate the design of a 2-microgrid interface using a dynamic phasor model, which we show to be more accurate than the reduced order VSC model commonly used in microgrid analyses. The interface can also alter the steady state power flow between microgrids to suit energy management strategies in a smart grid. Finally, we present simulation and experimental test results of the interface operation.