الفهرس 
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Abstract
With their extensive and growing utilization in power systems, renewable energy generators (REG) affect power system dynamics and stability. This thesis presents the impact of REG on power system dynamics especially through their effect on reducing overall system inertia. Low inertia of high REG-penetrated systems makes them more affected by power inequalities and suffer from worse frequency deviations. The effect of inertia on system frequency dynamics is analyzed using a simplified model of microgrids. In addition, the possibility of estimating system inertia through online measurements depending on the well-known swing equation is discussed and illustrated in the thesis. Inertia estimation is convenient to determine how much the system is initially stable against frequency events, before other frequency controllers operate. Virtual inertia controllers represent the main solution regarding lack of system inertia. The concept of virtual inertia is presented followed by a literature review of previous virtual inertia controllers. The thesis focuses on synchronous converter (synchronverter) because it is currently one of the most promising grid-friendly inverters that mimics synchronous generators. In addition to providing some virtual inertia for enhancing system frequency, synchronverter (SV) can also improve voltage profile of the system. But, it depends on a virtual current to achieve self-synchronization with grid voltage which produces a complicated controller that lacks plug-play capability. This thesis proposes a new generation of self-synchronized SVs with no need to a virtual current. In this thesis, an additional speed loop representing a virtual prime mover is introduced to eliminate the virtual current from the controller. This results in a simpler controller which provides plug-play capability with no need for switching between actual controller current and a virtual current. A linearized small-signal model is derived for the proposed synchronverter (PSV) to investigate its stability. The PSV is also validated through multiple simulation studies carried out in MATLAB/SIMULINK environment. The results show the capability of the PSV to achieve self-synchronization and plug-play operation without a Phase-locked loop (PLL) or a virtual current. Compared to the current self-synchronized SV, the PSV guarantees a smoother grid connection and gives more accurate reactive power sharing. Moreover, the PSV is applied to modified.