Control of Voltage-Source Converters Considering Virtual Inertia Dynamics

Controlling power-electronic converters in power systems has significantly gained more attention due to the rapid penetration of alternative energy sources. This growth in the depth of penetration also poses a threat to the frequency stability of modern power systems. Photovoltaic and wind power systems utilizing power-electronic converters without physical rotating masses, unlike traditional power generations, provide low inertia, resulting in frequency instability. Different research has developed the control aspects of power-electronic converters, offering many control strategies for different operation modes and enhancing the inertia of converter-based systems. The precise control algorithm that can improve the inertial response of converter-based systems in the power grid is called virtual inertia. This thesis employs a control methodology that mimics synchronous generators characteristics based on the swing equation of rotor dynamics to create virtual inertia. The models are also built under different cases, including grid-connected and islanded situations, using the swing equation with inner current and voltage outer loops. Analysis of the simulation results in MATLAB/Simulink demonstrates that active and reactive power are independently controlled under the grid-imposed mode, voltage and frequency are controlled under the islanded mode, and frequency stability of the system is enhanced by the virtual inertia emulation using swing equation. On this basis, it is recommended that the swing equation-based approach is incorporated with the current and voltage control loops to achieve better protection under over-current conditions. Further works are required to discover other factors that could improve the effectiveness of the models