Microgrids can operate in grid-tied mode and islanded mode with different load conditions. During the transition from one operating mode to another or varying load conditions, small disturbances may occur in the system, which can create transient oscillations due to the insufficient inertia of the distributed generating units (DG) of the microgrid. The droop control is mainly adapted to govern the working of the microgrid and maintain stability and power supply to the load. This paper presents an optimization-based control approach for the smooth operation of microgrids during the transition from one operating mode to another. The eigenvalue analysis and participation factors are used to find the control parameters for improving the power-sharing and stability of the microgrid. The modified PSO (MPSO) with adaptive weighted delayed velocity function (PSO-AWDV) is utilized to optimize the integral time square error (ITSE) of real and reactive power of the DGs in the microgrid. The eigenvalues analysis and time-domain simulation are presented to show the performance of the proposed approach for resistive and resistive-inductive load scenarios. The outcomes unveil that the optimized droop parameters improve the performance of DGs in microgrid by reducing overshoots in the range of 0.5% to 6% in real power, reactive power, output voltage, and currents of DGs as compared to parameters selected based on conventional approach. Moreover, the settling time for all the variables is reduced to 0.2 s with the proposed controller that enhances the steady state response of the system.
Key words: Microgrid; Droop controller; Stability; Modified particle swarm optimization; Power sharing; Eigenvalue analysis.
|
