All the wind turbines in aggregate sure seems like enough rotating mass if you are using the right type of generator and properly set up the controls.,(reply>), They cannot provide inherent (no delay) inertia since they are decoupled from the grid but they could provide synthetic inertia (through power converter controls). However, synthetic inertia has a lot of issues (measuring df/dt - time delays due to filtering, limited wind turbine rotor speed deviations, non-ideal tip speed ratio - second frequency dip...),(reply>), Actually that would make things worse. Because synchronous generators are reversible, when the wind wasn't blowing quite right then the generator would act as a motor and suck power from the grid to keep turning at 50Hz, and because wind comes in gusts it'll never quite be blowing right. That's why actual wind turbines don't use synchronous generators and don't contribute to grid stability.