An energy management system comprises a first electricity transformer with one or more first leg circuit(s), a second electricity transformer with one or more second leg circuit(s), and a control device. One or more first leg circuit(s) is (are) coupled to an energy-type supply, and one or more second leg circuit(s) is (are) coupled to a power-type supply. The control device will control the first and second electricity transformers operating under at least one of two conditions when a traction device is under driving mode.