System for charging an energy store, and method for operating the charging system

An energy supply network, comprising:

• a controllable first energy reservoir which serves to control and supply electrical energy to an n-phase electrical machine, where n≧1, the first energy reservoir having n parallel energy supply branches which (i) each have at least two energy reservoir modules connected in series, each energy reservoir module encompassing at least one electrical energy reservoir cell having an associated controllable coupling unit, (ii) are connectable on the one hand to a reference bus, and (iii) are connectable on the other hand to a respective phase of the electrical machine, wherein, as a function of control signals, the coupling units one of bypass the respectively associated energy reservoir cells or switch the respectively associated energy reservoir cells into the respective energy supply branch;
• a second energy reservoir from which electrical loads are supplied with DC voltage;
• and
• a charging device for the second energy reservoir, wherein the charging device is connectable (a) on an input side to the energy supply branches of the first energy reservoir and to the phases of the electrical machine, and (b) on an output side to the second energy reservoir,
• wherein the charging device includes:
• an n-phase rectifier unit having n parallel rectifier branches which are each connected to an energy supply branch and to the associated phase of the electrical machine;
• a link circuit capacitor downstream from the rectifier unit and fed from the rectifier unit;
• and
• a first DC voltage converter which is downstream from the link circuit capacitor and adapts a first voltage level of the link circuit capacitor to a second voltage level of the second energy reservoir,
• wherein the first DC voltage converter is provided without galvanic isolation, and wherein the second energy reservoir is configured as a high-voltage energy reservoir,
• a second DC voltage converter which is downstream from the second energy reservoir;
• and
• a third energy reservoir downstream from the second DC voltage converter;
• wherein the second DC voltage converter adapts the second voltage level of the second energy reservoir to a third voltage level of the third energy reservoir downstream from the second DC voltage converter, and
• wherein electrical loads are supplied with a DC voltage at the third voltage level from the third energy reservoir.