1. 20EE603PE-ELECTRIC VEHICLES
UNIT-II
HYBRID POWER TRAIN TOPOLOGYAND DYNAMICS
CONTENT
Introduction to Basic architecture
Architecture of Hybrid Electric Vehicles
Hybrid based on Transmission Assembly
Analysis of drive trains and power flows
Drive cycle implications and fuel efficiency estimations
Sizing of components for different hybrid drive train topologies
Topologies for electric drive train
Fuel efficiency estimations and wheel to wheel fuel efficiency
analysis
Sizing of components for different electric drive train topologies
3. . Architecture of Hybrid Electric Vehicles
1. Series Hybrids
Advantages :
• Flexibility of location of engine-generator set.
• Simplicity of drivetrain.
• Suitable for short trips with stop and go traffic.
Disadvantages :
• It needs three propulsion components: IC engine, generator and motor.
• The motor must be designed for the maximum sustained power.
• All three drivetrain components need to be sized for maximum power for long-distance
sustained, high-speed driving.
4. 2. Parallel HEV powertrain
Advantages :
• It only needs two propulsion components: IC engine and motor. In parallel HEV, motor
can be used as generator and vice versa.
• A smaller engine and a smaller motor can be used to get the same performance, until
batteries are depleted.
Disadvantages:
• The control complexity increases significantly, since power flow has to
Be regulated and blended from two parallel sources.
• The power blending from the IC engine and the motor necessitates a
complex mechanical device.
6. HYBRID BASED ON TRANSMISSION ASSEMBLY
Pre-and Post –transmission Hybrids
Figure. Power-split pre-transmission hybrid configuration
Figure. Parallel post-transmission hybrid configuration
7. P0-P4 Hybrid Architectures
Figure. HEV P0 to P4 architectures: (a) P0 architecture with belt starter generator;
(b) P1 architecture ISG; (c) P2 architecture and (d) P3 or P4 architecture
8. 48V Hybrid Architectures
• The 48V architectures are a less disruptive approach of vehicle electrification for
increasing fuel economy and reducing carbon emissions with 48V powertrain
electrification.
Hybrid Based on Degree of Hybridization
• There are three ‘mission-based’ classes: mild hybrids, power hybrids and
energy hybrids.
• The ‘mild’ hybrids have the lowest degree of hybridization with a moderate
effect on fuel economy and emissions.
• The ‘power’ hybrids have a larger electric propulsion component, with an
electrical rating as high as 40 kW; these hybrids allow significant amount
of power transfer between battery and motor drive system, although the
battery storage is designed with relatively low energy capacity (3–4 kWh).
• The ‘energy’ hybrid employs a high-energy battery system capable of
propelling the vehicle for a significant range without engine operation.
• The electrical rating and battery capacity are typically in the ranges of
70–100 kW and 15–20 kWh.
9. ANALYSIS OF DRIVE TRAINS AND POWER FLOWS
Figure. Electric vehicle drive-train power flow model
10. DRIVE CYCLE IMPLICATIONS AND FUEL EFFICIENCY ESTIMATIONS
Figure. Fuel cell inputs and outputs
The electrical power and energy output are easily calculated from
𝑃𝑜𝑤𝑒𝑟 = 𝑉𝐼 𝑎𝑛𝑑 𝐸𝑛𝑒𝑟𝑔𝑦 = 𝑉𝐼𝑡
• At a simple level it is the ‘chemical energy’ of the H2, O2 and H2O.
• The ‘chemical energy’ is not simply defined and terms such as enthalpy,
Helmholtz function and Gibbs free energy are used.
• The enthalpy H, Gibbs free energy G and entropy S are connected by the
well-known equation
𝐺 = 𝐻 − 𝑇𝑆
11. .
• The energy that is released by a fuel cell is the change in Gibbs energy before
and after a reaction – so the energy released can be represented by the equation
∆𝐺 = 𝐺𝑜𝑢𝑡𝑝𝑢𝑡𝑠 −𝐺𝑜𝑖𝑛𝑝𝑢𝑡𝑠
Table. shows ∆𝐺 for the basic hydrogen fuel cell reaction
𝐻2 +
1
2
𝑂2 → = 𝐻2 𝑜
• The efficiency of a fuel cell as
𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑
𝐺𝑖𝑏𝑏𝑠 𝑓𝑟𝑒𝑒 𝑒𝑛𝑒𝑟𝑔𝑦 𝑐ℎ𝑎𝑛𝑔𝑒
• This is called the ‘calorific value’, though a more precise description is the change in
‘enthalpy of formation’. Its symbol is ∆H.
• The efficiency of the fuel cell is usually defined as
𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑎𝑙 𝑒𝑛𝑒𝑟𝑔𝑦 𝑝𝑟𝑜𝑑𝑢𝑐𝑒𝑑 𝑝𝑒𝑟 𝑚𝑜𝑙𝑒 𝑜𝑓 𝑓𝑢𝑒𝑙
−∆𝐻
12. Form of Water
product
Temperature
(℃)
∆𝑮 (KJ mol-1)
Liquid 25 -237.2
Liquid 80 -228.2
Gas 80 -226.1
Gas 100 -225.1
Gas 200 -220.4
Gas 400 -210.3
Gas 600 -199.6
Gas 800 -188.6
Gas 1000 -177.4
Table. ∆G for the reaction 𝑯𝟐 +
𝟏
𝟐
𝑶𝟐 → = 𝑯𝟐 𝒐 at various temperatures
For the ‘burning’ of hydrogen
𝐻2 +
1
2
𝑂2 → = 𝐻2 𝑜 (steam)
∆𝐻 =−241.83 kJ mol−1
13. whereas if the product water is condensed back to liquid, the reaction is
𝐻2 +
1
2
𝑂2 → = 𝐻2 𝑜 (liquid)
∆𝐻 =−285.84 kJ mol−1
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑝𝑜𝑠𝑠𝑖𝑏𝑙𝑒 =
∆𝐺
∆𝐻
× 100%
𝑀𝑎𝑥𝑖𝑚𝑢𝑚 𝑒𝑓𝑓𝑖𝑐𝑖𝑒𝑛𝑐𝑦 𝑝𝑜𝑠𝑠𝑖𝑏𝑙𝑒 =
∆𝐺
∆𝐻
× 100%
Figure. The reactions at the electrodes, and the electron movement, in a fuel
cell with an acid electrolyte
