A Distributed Secondary Control Approach for Inverter-Dominated Microgrids With Application to Avoiding Bifurcation-Triggered Instabilities

The distributed secondary control is applied in an inverter-dominated microgrid (MG) for compensating the voltage and frequency deviations caused by the operation of the primary droop-based control. Despite the flexibility and reliability of the controllers, the low-inertia nature of voltage source inverters threatens the system stability against probable disturbance. Therefore, it is necessary to analyze the stability of islanded MG by focusing on the hierarchical control structure. The effect of the distributed secondary control on the stability margin of the MG using bifurcation analysis when parameters change is investigated in this article. To this end, this article firstly derives a precise dynamic model of the MG with the secondary control level. Next, the eigenvalues of the system state matrix are analyzed to determine the dominant parameters affecting the stability. Then, the bifurcation theory is used to predict the parameter stability margin with/without secondary control. By changing the parameters, the Hopf and saddle-node bifurcations are detected in the system. Finally, the simulation and experimental results confirm the effectiveness of the distributed secondary control in preventing the occurrence of bifurcation.