*2.1.3. Fuel cell vehicle based electric drives*

**2. Configurations and components of electric drives in AFVs**

**Figure 1.** The configuration of hybrid energy storage system(HESS)-based electric vehicle

management algorithms, respectively.

The topology of hybrid energy storage system is shown in Figure 1. Ultracapacitor and DC/DC converter are in series connection, with battery parallelly connected to the DC bus [8].

Hori [9], [10] adopted a heuristic control approach based on vehicle speed by taking into account ultracapacitors' energy utilization efficiency. Wang and Deng, et al. [8] adopted an optimization method for power distribution with the objective of minimum battery energy loss as the optimization goal. Ortuzar and Moreno [11] adopted heuristic algorithm based on two main rules and optimized algorithm obtained from a neural network as the energy

*2.1.1. Electric drives for pure electric powertrain with battery, ultracapacitor, or Hybrid Energy Storage*

During the AFV running, the load profile consists of high current peaks and steep valleys due to the repetitive starting, acceleration, and braking in the urban driving cycle. Thus, the battery alone faces several challenges: 1) huge addition to the battery numbers to meet the peak power demand; 2) severe adverse effect on battery life because of frequent charge or discharge operations; 3) extra difficulty on battery thermal management in high-power-load situation [5].

The ultracapacitor has much higher power density, longer cycle life, lower temperature sensitivity, higher efficiencies, but lower energy density, which makes it an attractive pairing

**2.1. Electric drive configurations in various powertrains**

*System (HESS)*

4 New Applications of Electric Drives

for batteries [6], [7].

The fuel cell powered hybrid drive train [12], [13] mainly contains a fuel cell system, a proton power system (PPS), an electric motor and accordingly motor control unit (MCU), a vehicle control unit (VCU), and a power converter between the fuel cell stack and the proton power system. After the accelerator, the braking pedal or other operating signals provide the power or torque command, the motor output power or torque is controlled by the VCU, as well as the energy flows between the fuel cell stack, the proton power system, and the drive train.
