The present invention relates to an energy storage converter grid-connected/off-grid mode operation controller, and a control method and device of the controller. According to the controller, an alphabeta/dq coordinate converter, a power calculation unit and a power outer loop control unit are sequentially connected with one another; the power outer loop control unit and an synchronization control unit are both connected with a voltage inner loop control unit through a first adder and a second adder; and the voltage inner loop control unit, a dq/alphabeta degree converter and an SVPWM module are sequentially connected with one another. The present invention aims to avoid the unreliable switching of the grid-connected/off-grid mode operation mode of an energy storage converter caused by control architecture change which is further caused by the switching of the grid-connected/off-grid mode operation mode of the energy storage converter.