6 Electric and Hybrid Vehicles Transmission Wheels Coupling Devices Internal Combustion Engine Electric Generator MPTP Electric Machine and Drive Wheels Coupling Devices Energy Storage EPTP FIGURE 1.4 An HEV powertrain. the EPTP, or the combination of the two. The MPTP is associated with an IC engine and transmis- sion, whereas the EPTP consists of the energy storage system, a generator, a propulsion motor and transmission. The combination of electric machines and IC engine and the arrangements of the power transmission paths give rise to a variety of architectures for HEVs.
The energy sources and the power conversion devices can be arranged in series, parallel or a series–parallel combination giving rise to these various hybrid architectures. The hybrid vehicle architectures are discussed in Chapter 3. The arrangement of the electrical components of the generic hybrid vehicle is shown in Figure 1.5. The electric generator shown in the hybrid configuration of Figure 1.5 is coupled to the engine and can be operated either as a generator or as a motor. During generation, the power through the gen- erator can be used to charge the energy storage using a bidirectional inverter, or to deliver energy directly to the propulsion motor through the DC bus.
The generator can also be operated as a motor during engine starting and torque boosting to meet driver peak acceleration demands. The energy storage system will absorb or deliver power depending on the system state of charge and driving conditions. Another bidirectional inverter conditions the power flow for the propulsion motor, which delivers torque to the wheels. The propulsion motor can also capture regenerative energy during vehicle braking. The energy storage devices used in hybrid vehicles are presented in Chapters 5 and 6. The starter-generator and propulsion motor in the EPTP use high-power electric machines.
These electric machines need to have motoring and generating capability, high power density, high efficiency and high starting torque over a wide speed range to meet the performance specifications. The different types of electric machines are discussed in Chapter 7, while the machine control- ler methods and the electric drives are presented in Chapters 8 and 10, respectively. The power FIGURE 1.5 Electrical components of an HEV. Electric Propulsion Generator Motor Bi-directional Bi-directional Inverter Inverter Power Power DC B Power Energy Storage