This study proposes a capacitor voltage synchronising control-based virtual synchronous generator (CVS-VSG) scheme for the inertial and primary frequency responses of type-4 wind turbine generators (WTGs) in wind power-dominated power systems. The CVS-VSG scheme is realised on type-4 WTGs based on the equations of motion of capacitor voltages. The type-4 WTGs are controlled as VSGs to emulate the inertial and primary frequency responses of conventional SGs. Active load sharing between Type-4 WTGs is achieved by a governor with capacitor voltage droop characteristics. Modal analysis was carried out on a test system with 73.58% wind power penetration. Simulation studies were undertaken to evaluate the performance of the CVS-VSG scheme on the test system subject to large disturbances.