Week 2 Session 7

Compare the different architectures of HEV. Discuss the pros and cons.

Depending on DOH(degree of hybridization),

[DOH=motor power/motor power +ice power]

HEV can be classified as mild, micro, and full HEV.

Types of vehicle	Engine start/stop	Regenerative braking	Motor assist	Electric drive
Micro-hybrid	Yes	Slight	Slight	No
Mild-hybrid	Yes	Yes	Yes	No
Full-hybrid	Yes	Yes	Yes	Yes

Based on architecture, HEV can be classified as :

Series HEV:

In this system, the only element connected to the transmission system is the motor, there is no direct connection between ICE and the transmission. The role of ICE is to produce power through a generator, and the output of the generator is given to either batteries or motors.

Advantages: no multi-ratio gearbox required

Disadvantages: Two-time energy conversion is required which reduces efficiency.

Parallel HEV:

Both motor, as well as ICE, is connected to the transmission system. It can work in both Engine mode as well as battery mode or partially by ICE and partially by battery. During regenerative braking, the mode motor works as a generator and charge the batteries

Example: It is very popular Hev, most commercial vehicles and passenger cars use this architecture

Series -Parallel architecture(Power Split):

In this architecture, there are two paths

The series path from the engine to the vehicle: The engine is going to produce power from fuel in the tank and propel the transmission system

The parallel path from Battery to the wheels through the power split: The motor is going to provide the propulsion power by using power from the battery through the power converter unit.

This architecture decides which mode should be selected depending on Fuel or SOC of the battery

Example: Toyota Altis

advantages: High efficiency.