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In Part I of this two-part paper, a power-management and a control strategy for the microgrid autonomous mode of operation were presented. The strategy consists of 1) open-loop frequency control of the system and synchronization of DER units based on a GPS signal; 2) voltage reference setpoint determination for the DER units by the central power-management system; and 3) tracking the assigned setpoints and rejecting disturbances by robust, decentralized, local controllers of DER units. This Part II paper applies the envisioned strategy to a three-DER microgrid. Offline digital time-domain simulation studies in the EMTDC/PSCAD software environment demonstrate the robustness of the local controllers to parametric, topological, and unmodelled uncertainties of the microgrid, its fast performance in tracking the setpoints with zero steady-state error, and rapid disturbance rejection. The results also show the effectiveness of the proposed power-management system in achieving prescribed load sharing of DER units. The digitized algorithms of the proposed control system of the three-DER microgrid are also implemented in NI-cRIO industrial-grade platforms and tested in an RTDS-based real-time hardware-in-the-loop (HIL) environment to demonstrate the feasibility of the strategy for hardware implementation and hardware-based performance validation.
Date of Publication: Oct. 2012