A control strategy for islanded operation of a Distributed Resource (DR) unit

This paper proposes a mathematical model and a voltage/frequency regulation strategy for an islanded, electronically-coupled, distributed resource (DR) unit. The DR unit can either represent a distributed storage (DS) unit or a dispatchable distributed generation (DG) unit. The proposed control strategy benefits from the power circuit configuration, dq-frame current-control scheme, and the phase-locked loop (PLL) mechanism that exist and are optimized in modern grid-connected DR units. Therefore, the proposed control strategy requires minimal software modifications to enable the operation of the DR unit in the islanded mode, with black-start capability, for example, for a remote microgrid application. In addition, the proposed control strategy employs feed-forward techniques to mitigate the impacts of (i) load dynamics on the system stability and performance, and (ii) inherent inter-couplings and nonlinearities of the control system. This, in turn, remarkably facilitates the controller design procedure. The principles supporting the proposed control strategy are discussed and analyzed, and the effectiveness of the control is demonstrated through digital time-domain simulations conducted on a detailed switched model of a 5. 0 MVA DR unit.