Sharif Digital Repository

This article presents a comprehensive small signal model for a virtual synchronous generator (VSG) integrated into a microgrid. In the developed state-space, active and reactive power control loops of the VSG as well as resistances, and reactances of the lines are considered. Based on this model, the robust D-stable region in terms of different values of inertia constant $(M)$, and damping coefficient $(D)$ values of the VSG is obtained. To enhance both transient performance as well as guarantee the robust D-stable operation of VSG, an optimization problem is also proposed. Moreover, a new control method is suggested to damp frequency oscillations of the microgrid. The proposed controller is... 

This paper presents a robust decentralized proportional-integral (PI) control design as a solution of the load frequency control (LFC) in a multi-area power system. In the proposed methodology, the system robustness margin and transient performance are optimized simultaneously to achieve the optimum PI controller parameters. The Kharitonov's theorem is used to determine the robustness margin, i.e., the maximal uncertainty bounds under which the stable performance of the power system is guaranteed. The integral time square error (ITSE) is applied to quantify the transient performance of the LFC system. In order to tune the PI gains, the control objective function is optimized using the... 

This paper first discusses dynamic characteristics of wind turbines with doubly fed induction generator (DFIG). Rotor back electromotive force (EMF) voltages in DFIG reflect the effects of stator dynamics on rotor current dynamics, and have an important role on rotor inrush current during the generator voltage dip. Compensation of these voltages can improve DFIG ride-through capability and limit the rotor current transients. It is found that the electrical dynamics of the DFIG are in nonminimum phase for certain operating conditions. Also, it is shown that the dynamics of DFIG, under compensation of rotor back EMF and grid voltages, behave as a partially linearizable system containing... 

In this paper, the aeroelastic analysis of a large scale wind turbine rotor is performed with the aim of studying transient performance of turbine in extreme wind conditions, such as wind gusts and rapid yaw changes. The effect of the presence and/or lack of blade pitch control system on output power, rotor thrust, and blade deformation in sudden change of wind speed are investigated. The NREL 5 MW offshore wind turbine is used as the baseline case. In this regard, the modal approach is implemented for modeling the flexible blade structure with tension, bending and torsion degrees of freedom. The unsteady vortex lattice method is employed to obtain the aerodynamic loads. Moreover, the...