The invention relates to a virtual synchronous control method and a rotor-side frequency converter controller. The method comprises the steps of determining a virtual inert mass response state constraint factor of a doubly-fed wind turbine generator according to a system frequency change of the doubly-fed wind turbine generator; correcting a rotation speed of a virtual synchronous machine of the doubly-fed wind turbine generator by use of a correction equation for the rotation speed of the virtual synchronous machine of the doubly-fed wind turbine generator; and performing virtual synchronouscontrol on the doubly-fed wind turbine generator according to the corrected rotation speed of the virtual synchronous machine, wherein the correction equation for the rotation speed of the virtual synchronous machine of the doubly-fed wind turbine generator is determined according to the virtual inert mass response state constraint factor of the doubly-fed wind turbine generator. According to themethod provided by the invention, for the problem of reduction of inertia of a grid-connected system caused by grid connection of the large-scale doubly-fed wind turbine generators, the anti-interference capability and stability of the doubly-fed wind turbine grid-connected system can be improved.