In a multiphase electrical power assignment, a processor: receives instructions to connect a bi-directional power device to a multiphase premise power source; determines that the power device is to be coupled to a target phase's phase connection; confirms that the power device is not coupled to any phase connections; and couples the power device to the phase connection, where the power device's power signal is synchronized with the phase connection's power signal. When the power device is in a connected state, the processor: issues a command to place each phase connection switch in an open state; in response to confirming that the phase connection switches are in the open state, issues commands to the power device so that a power signal of the power device will be synchronized with the target phase; and closes the phase connection switch corresponding to the target phase.