Virtual Inertia, Virtual Damping, and Fault Ride‐through

This chapter shows that the concept of inertia has two aspects of meaning: the inertia time constant that characterizes the speed of the frequency response and the inertia constant that characterizes the amount of energy stored. It also shows that, while the energy storage aspect of the virtual inertia of a virtual synchronous machine (VSM) can be met by storage units, the inertia time constant that can be provided by a VSM may be limited because a large inertia time constant may lead to oscillatory frequency responses. A virtual damper is introduced to provide the desired damping ratio, together with the desired inertia time constant. Two approaches are presented to implement the virtual damper: one through impedance scaling with a voltage feedback controller and the other through impedance insertion with a current feedback controller. A by‐product from this is that the fault ride‐through capability of the VSM can be designed as well.