An energy management system that includes a power generating device, bidirectional DC-DC converter, and inverter connected to an HVDC bus. A gain of a voltage change to a current change in the bidirectional DC-DC converter is equal to the gain in the inverter. When an output power of the inverter or the bidirectional DC-DC converter varies in response to a variation in an output current of the power generating device, the energy management system can control the output power of the inverter to conform to a target value by adjusting an offset of gain characteristics of the bidirectional DC-DC converter to gain characteristics of the inverter. As a result, the energy management system is capable of stabilizing the output power of the inverter.