Coordinating the Frequency-Droop Controls of Inverter-Based Resources and Diesel Generators in an Isolated Microgrid

With the increasing penetration level of renewable energy sources (RESs), microgrids (MGs) implemented with inverter-based resources (IBRs) and diesel generators (DGs) are considered to be new solutions to supply power in remote areas and islands. Despite the introduction of power and voltage balancing services for distributed energy resources (DERs) and DGs in recent standards and codes, the coordination between the services provided by DERs and DG is not thoroughly investigated. This paper assesses the frequency-droop control defined in IEEE 1547-2018 std. for a DER, investigates the coordination between the DER's and DGs' droop controls, and reveals a risk of malfunction-exaggerating frequency deviation and power waste-if their droop controls do not coordinate well. Furthermore, this paper presents a frequency-restoration function to resolve the observed malfunction. The coordination of DER's and DG's control parameters is also examined. Moreover, the power sharing between multiple DGs and DERs during significant load changes is investigated. Simulation results show that the presented frequency-restoration function, suggested control parameters, and developed power sharing method can significantly benefit the coordination of multiple DERs and DGs in an isolated MG.