A system for charging at least one energy reservoir cell in a controllable energy reservoir which serves to control and supply electrical energy to an n-phase electrical machine where n≧1. The controllable energy reservoir has n parallel energy supply branches that each have at least two energy reservoir modules, connected in series, that each encompass at least one electrical energy reservoir cell having an associated controllable coupling unit, and are connected to a reference bus and to a respective phase of the electrical machine. As a function of control signals, the coupling units interrupt the respective energy supply branch, bypass the respectively associated energy reservoir cells, or switch the respectively associated energy reservoir cells into the respective energy supply branch.