A system includes a generator configured to be electrically coupled to a grid, a transmission configured to mechanically couple the generator to a prime mover, a converter circuit configured to be electrically coupled between the grid and an energy storage device, and a controller configured to control the converter circuit and the transmission. The controller may operate the converter circuit to source or sink power in response to a change on the grid meeting a criterion. The controller may be further configured to adjust a transmission ratio of the transmission based on a demand on the generator. The controller may also be configured to cause the transmission to mechanically decouple the generator from the prime mover while maintaining an electrical coupling of the generator to the grid so that the mechanically decoupled generator can contribute current to a fault on the grid.