I. Introduction
Virtual synchronous generator (VSG) gets increasingly interest from researchers since it can supplement the lack of inertia in a power-electronics microgrid, while it reaches the goal of primary frequency control (PFC) [1]. In the previous research, the parameter design of VSG is subject to the output impedance of inverter, line impedance, the voltage at output terminal and the point of common coupling, even the initial power angle. It should be noticed that many of these parameters are time-variant and too hard to access, thus brings much inconvenience for manufacturers to set parameters [2]–[4], [6]. The main reason is that active power is not the primary regulating target, but the rotor frequency, also it doesn’t be discriminated. Although an integrator is applied to realize SFC [5], it doesn’t explore the parameter design method. So, the parameter design method still needs to be discussed and simplified while VSG is under SFC mode.