Abstract: A method for charging and/or discharging energy storage devices is performed in a multilevel converter including at least one phase module branch having a series circuit of submodules each with at least one power semiconductor circuit for connection or disconnection of an energy storage device in a circuit parallel to the power semiconductor circuit and a submodule sensor for detection of an energy storage actual value. An energy change state is obtained and a determination is made as to whether connected energy storage devices in a phase module branch can be charged or discharged. The next energy storage device to be switched in each phase module branch is selected by predetermined logic dependent on an energy change state, through which energy stored in energy storage devices is kept approximately at the same level. A high clock rate is simultaneously avoided for connection and disconnection of the selected energy storage device.

Abstract: A device for inverting an electric current has at least one phase module which has an alternating current connection and at least one direct current connection. Semiconductor valves having semiconductor modules are connected in series and are provided for switching the electric current between the alternating current connection and each direct current connection. At least one power storage device is provided for storing electrical power. In order to provide such a device, with which the adverse effects of a bridging short circuit are reliably and effectively reduced, it is proposed that each semiconductor module has semiconductor groups connected in parallel to each other, wherein each semiconductor group of the semiconductor module is connected via its own separate semiconductor current path to at least one of the power storage devices.

Abstract: A converter has at least one phase module, an AC voltage terminal and a DC voltage terminal. A phase module branch is formed between each DC voltage terminal and each AC voltage terminal. Each phase module branch has a series circuit containing submodules which each have a capacitor, a power semiconductor, and submodule sensors for detecting energy stored in the capacitor and with a regulation device for regulating the apparatus in dependence on energy values and predetermined desired values. Therefore unbalanced loading of the energy storage units is avoided. The regulation device has a summation unit for summing the energy values while obtaining branch energy actual values and a device for calculating circuit current desired values in dependence on the branch energy actual values. The regulation device compensates for imbalances in the branch energy actual values in dependence on the circuit current desired values.