Case Studies on Cascade Voltage Control of Islanded Microgrids Based on the Internal Model Control

Erratic variations of the load and step changes of the voltage reference value usually impose voltage transients to the microgrid. These transients prevent effective utilization of the electric power delivery infrastructure and cause violation of the limits. Furthermore, some industrial loads are very susceptible to these unpredictable variations of the voltage. This paper proposes an innovative approach to improve the transient behavior of the three-phase voltage of a distributed generation (DG) unit in an islanded microgrid. The proposed approach has a cascade control structure, which consists of an inner current control feedback loop and an outer voltage control feedback loop. Both control loops are developed based on the internal model control (IMC) approach. Several simulation case studies confirm that the proposed IMC-based approach has superior transient performance compared with the conventional PI-based voltage control approach.