An Overview of Virtual Inertia and Its Control

RoCoF-Minimizing H₂ Norm Control Strategy for Multi-Wind Turbine Synthetic Inertia

“…Note that the system (5) contains the derivatives of the original state vector, so defining C = [1 0 0 0] and D = 0, the output performance signal z is the derivative of the frequency, that is, z = ∆ ḟ = RoCoF. Because of that, the transference matrix function G(•), between w and z for system (5) represents the relation between the impulse signal ∆ Ṗ and the RoCoF energy, which is the energy of the frequency RoCoF. Thus, from the H 2 control approach theory, it is possible to design a control gain K i in order to minimize the RoCoF energy while guaranteeing stability for system (5).…”

“…Because of that, the transference matrix function G(•), between w and z for system (5) represents the relation between the impulse signal ∆ Ṗ and the RoCoF energy, which is the energy of the frequency RoCoF. Thus, from the H 2 control approach theory, it is possible to design a control gain K i in order to minimize the RoCoF energy while guaranteeing stability for system (5). for a given gain matrix K i , the H 2norm for the G(•) is given by:…”

“…From the optimal control theory, a Linear Quadratic Regular (LQR) control approach can be considered [29]. The LQR control aims to compute a feedback proportional control gain K for system (5) in order to minimize the quadratic cost functional J given by:…”

Fault-Ride-Through Approach for Grid-Tied Smart Transformers without Local Energy Storage

“…In comparison with the high voltage values of the MV DC bus, the forward voltage drop in the four-diode bridge and in the electronic switch during its on-state (t on ) are much smaller, to the point of being negligible. Thus, the voltage drop in the electronic resistor can be approximated by Equation (5), where V EZ is the voltage drop in the electronic resistor, V L the voltage drop in the inductor, V MOV the voltage drop in the MOV, t on is the on-state period of the electronic switch, and t off is the off-state period of the electronic switch. t on and t off are related to the switching period T s and switching frequency f s according to Equation (6).…”

“…The expected increase of Distributed Energy Resources (DER) in distribution grids, such as Renewable Energy Sources (RES), Electric Vehicles (EV) and distributed Energy Storage Systems (ESS), is highlighting new challenges regarding operation and control of electric power systems [1][2][3][4][5]. In order to face this new paradigm, advanced concepts aimed to improve controllability and observability of distribution grids have been proposed, such as the microgrid, being regarded as the building block of the broader smart-grids concept [6][7][8][9][10][11].…”