The increasing share of renewable energy sources causes a reduction of inertia provided by conventional synchronous generators to the grid. To enable a stable operation in converter dominated grids a replacement of the inertial response of synchronous generators is required. This paper introduces a new energy storage system for high power, which provides synthetic inertia by charging or discharging a flywheel connected to a doubly fed induction generator. The authors discuss why the Modular Multilevel Matrix Converter (M3C) is an attractive topology to drive the flywheel. Experimental results of a downscaled 10 kVA test bench with a M3C containing 108 submodules verify the function of the new energy storage system. on a downscaled 10 kVA test bench with a 108 submodule M3C.