Effect of inverter-based DG penetration and control in hybrid microgrid dynamics and stability

This paper presents a study on the effect of increasing the inverter-based Distributed Generators (DGs) penetration in the dynamics and stability of a hybrid Microgrid. An analysis is also done to compare different inverter control techniques as a way to reduce voltage and frequency variations after a disturbance. The purpose of this study is to compare Microgrids with different percentage of inverter penetration and propose methods to enhance stability. Results show that increasing penetration of inverters operated in slave mode, reduces stability. This is observed as oscillations and large settling times for voltage and frequency after disturbances such as islanding with power unbalance and fault-triggered islanding. Results also show that using droops in the inverter control loop can limit oscillations and reduce recovery times even beyond that of a system with large percentage of power generated with a synchronous machine. Finally, it is shown that if the inverter is operated so that its power factor matches that of the local loads, then stability increases.