Battery ultracapacitor based DC motor drive for electric vehicles

One of the main considerations for the EV drive train is to improve the efficiency of the motor drive. Each components of the power train should be properly designed so as to achieve the maximum efficiency and the desired driving performances. Since the battery's energy density is low, an ultracapacitor (UC) has been proposed to be used along with the battery to assist it during transient states and thereby increasing battery's capacity and lifespan. The voltage level and dynamic characteristic of the energy storage components are normally different from each other and therefore, a DC-DC converter has been incorporated into the vehicle drive train. The sizing of electrical storage components and controlling energy flow determines the overall efficiency and also its cycle life. Hence the frequency splitting based energy management algorithm has been used for the control of power flow across battery, ultracapacitor and the DC-link.