A method for controlled connection of a plurality of on-board power system branches is disclosed, wherein electrical power is exchanged between first and third on-board power system branches if an uncritical supply state is present and electrical power is exchanged between second and the third on-board power system branches if a critical supply state is present in the first or third on-board power system branch. In a critical supply state, the first on-board power system branch is disconnected from the third on-board power system branch by opening a first switching device, and the second on-board power system branch is then connected to the third on-board power system branch via a second switching device. A second actuation device that actuates the second switching device receives a switch state signal from the first actuation device and closes the second switching device only if the received signal signals an open first switching device.