An electric power conversion device for charging and discharging energy storage devices having at least one bidirectional voltage converter which can be connected to a power supply network and to at least one electrochemical energy converter for an energy storage device that is configured as a flow battery and has a circulation arrangement for electrolytes. The electric power conversion device has a controller connected to the voltage converter and is designed to control the voltage converter with regard to the power flow direction thereof. The controller is designed to control one or more energy storage peripheral devices associated with the electrolytes depending on the power flow direction of the voltage converter specified by the controller. The controller has at least one control port for connection of at least one of these energy storage peripheral devices.