Discussion on Instability of Current-controlled Inverter with df/dt-type Virtual Inertia Control

This paper focuses on the stability of a currentcontrolled inverter (GFL type) with df/dt-type virtual inertia control. The authors analyze the dynamic characteristics compared to those of synchronous generators and demonstrate the existence of a second-order delay between the electrical frequency and the rotor’s rotational frequency in synchronous generators. Then, this second-order delay is implemented into the df/dt-type virtual inertia control as a second-order low-pass filter (LPF), and the influence of the LPF is investigated by EMT simulation.