Discussion on Instability of Current-controlled Inverter with df/dt-type Virtual Inertia Control and a Design of the Stabilization Filter

This paper focuses on the stability of a current-controlled 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 phase and the rotor phase in synchronous generators. Then, this second-order delay is implemented into the df/dt-type virtual inertia control block as a second-order low pass filter (LPF). The influence of the LPF is investigated by EMT simulation. The simulation results demonstrate that the second-order LPF can improve the stability of df/dt-type virtual inertia control by setting proper parameters corresponding to synchronous generators.