PhD student T.G. Roberts with Advisor A. Domínguez-García

This research focuses on developing a suite of system level controls for the BANSHEE microgrid (Figure 26) and test them in a high-fidelity real-time controller hardware in the loop (C-HIL) setting (Figure 28).  This microgrid comprises synchronous generators on feeders 1 and 3 as well as a grid forming (GFM) inverter and grid following (GFL) inverter on feeder 2. GFM inverters are a promising technology for the replacement of rotating synchronous generators in the bulk power system as they can stabilize system voltage and frequency in microgrids with low inertia, unlike GFL inverters.  Because the BANSHEE system has heterogeneous generation, we can test both the functionality of inverter-based technologies working in tandem with synchronous generators, and the functionality of a GFM inverter operating autonomously (when feeder 2 is islanded).  The controls we have developed include secondary frequency and voltage control, tie-line power control, re-synchronization control, as well as discrete controls that facilitate mode changes.  The BANSHEE test system comprises three feeders with numerous circuit breakers on each feeder.  However, for analysis we distill the system into two feeders with a total of 4 circuit breakers (Figure 27).  This two-feeder system is the smallest test case that still comprises all controls present in the larger three feeder BANSHEE system.  With the two-feeder model we have a total of 7 modes that depend on the position of the 4 circuit breakers in the simplified model.  The modes are depicted in Figure 27, and they include grid connected mode, fully islanded mode, networked mode, partially islanded mode(s), and back fed mode(s).  Each arrow in the mode diagram represents a control action that can move the system from one mode to another by seamlessly opening/closing desired circuit breakers.  This research is funded by the U.S. Department of Energy.

Figure 26. BANSHEE distribution system. 

Figure 27. Top: Simplified tow bus system of the BANSHEE distribution feeder. This two feeder system is the smallest test case that still comprises all controls of the larger BANSHEE system. Bottom: Possible modes of the two feeder system.

 

Figure 28. Top: University of Illinois C-HIL lab, with controller hardware in the loop pictured, and BANSHEE microgrid simulation running. Bottom: Real-time simulation hardware used in the Illinois C-HIL lab.