Modeling and Simulation of Hybrid Electric Vehicles--混合动

Modeling and Simulation of Hybrid Electric

Vehicles

By

Yuliang Leon Zhou

B. Eng., University of Science & Tech. Beijing, 2005

A Thesis Submitted in Partial fulfillment of the Requirements for the Degree of

MASTER OF APPLIED SCIENCE

in the Department of Mechanical Engineering

? Yuliang Leon Zhou, 2007

University of Victoria

All rights reserved. This thesis may not be reproduced in Whole or in part, by photocopy or other means, without the permission of the author.

ii SUPERVISORY INFORMATION

Modeling and Simulation of Hybrid Electric Vehicles

By

Yuliang Leon Zhou

B.Eng., University of Science and Technology Beijing, 2005

Supervisory Committee

Supervisor

Dr. Zuomin Dong (Department of Mechanical Engineering) Department Member

Dr.

Suleman (Department of Mechanical Engineering) Afzal

Department Member

Rowe (Department of Mechanical Engineering)

Dr.

Andrew

External Examiner

Dr. Subhasis Nandi (Department of Electrical Engineering)

iii

Supervisory Committee

Zuomin

Engineering

Dong, Mechanical

Dr.

Supervisor:

Department Member: Dr. Afzal Suleman, Mechanical Engineering Department Member: Dr. Andrew Rowe, Mechanical Engineering

External Examiner: Dr. Subhasis Nandi, Electrical Engineering

Abstract

With increasing oil price and mounting environment concerns, cleaner and sustainable energy solutions have been demanded. At present transportation constitutes a large portion of the energy consumed and pollution created. In this work, two hybrid vehicle powertrain technologies were studied, a fuel cell - battery hybrid and two internal combustion engine - battery/ultracapacitor hybrids. Powertrain performance models were built to simulate the performance of these new designs, and to assess the feasibility of a fuel cell hybrid power backup system for a special type of vehicles, elevators in high-rise buildings, using the ADvanced VehIcle SimulatOR (ADVISOR) first. The model was then applied to evaluate the two-mode hybrid powertrain for more common vehicles - commercial trucks, showing potential fuel consumption reduction. To improve modeling accuracy, a new and more flexible tool for modeling multi-physics systems, Modelica/Dymola, was used to carry out the modeling and analysis of next generation hybrid electric vehicles, exploring the potentials of new hybrid powertrain architectures and energy storage system designs. The study forms the foundation for further research and developments.

iv

Table of Contents

Modeling and Simulation of Hybrid Electric Vehicles (i)

Supervisory Committee ............................................................................................... i i

iii Abstract .......................................................................................................... Table of Contents ........................................................................................................ i v

List of Figures (viii)

List of Tables (xiii)

List of Abbreviations .................................................................................................. x v Acknowledgements ................................................................................................... x vi CHAPTER 1 Introduction .. (1)

1.1. The Need of Hybrid Electric Vehicles (1)

1.1.1. Environmental Concerns (1)

1.1.2. Energy Consumption (2)

1.1.3. Current Global HEV Market (3)

1.2. HEV Classifications by Power Source (3)

1.2.1. Internal Combustion Engine Based HEV (4)

1.2.2. Fuel cell Based HEV (4)

1.3. HEV Classifications by Drivetrain Architectures (5)

1.3.1. Series Hybrid (5)

1.3.2. Parallel Hybrid (6)

1.3.3. Series-Parallel Configurations (9)

1.4. Thesis Outline (10)

CHAPTER 2 Review on Hybrid Electric Vehicles Energy Storage System (12)

2.1. Research Issues in Hybrid Electric Vehicles Design (12)

2.2. Energy Storage System (12)

2.2.1. Sizing Considerations of Energy Storage System (12)

2.2.2. ESS Power and Capacity Rating (13)

2.2.3. ESS for a Electric Vehicle (15)

v

2.2.4. ESS for a Hybrid Electric Vehicle (17)

2.2.5. ESS for a Plug-in Hybrid Electric Vehicle (18)

2.3. Advance of Energy Storage Technologies and Hydrogen Fuel Cells (19)

2.3.1. Sealed Lead Acid Battery (SLA) (20)

2.3.2. Nickel Metal Hydride Battery (Ni-MH) (20)

2.3.3. Lithium Ion Battery (Li-ion) (21)

2.3.4. Ultracapacitors (22)

2.3.5. Hydrogen Fuel Cells (22)

CHAPTER 3 Review on Vehicle Simulation Tools (24)

3.1. Vehicle Simulation Tools (24)

3.2. ADvanced VehIcle SimulatOR (ADVISOR) (24)

3.2.1. ADVISOR Background (24)

3.2.2. ADVISOR Modeling Approaches (25)

3.2.3. ADVISOR Interface (26)

3.2.4. Models in ADVISOR (30)

3.3. Modelica and Dymola (31)

3.3.1. Modelica (31)

3.3.2. Dymola (31)

3.3.3. Vehicle Modeling and Simulation Libraries (32)

CHAPTER 4 Modeling of a Fuel Cells Hybrid Power System for Elevator Power Backup Using ADVISOR (34)

4.1. Modeling High Speed Elevators as Electric Vehicles (34)

4.2. Power Failures of Elevators in High-rise Buildings (35)

4.3. Backup Power Solutions (36)

4.3.1. Batteries for Power Backup (37)

4.3.2. Ultracapacitors for Power Backup (37)

4.3.3. ICE Generator for Power Backup (38)

4.4. A Fuel Cells Hybrid Power Backup Solution (38)

4.4.1. A Hybrid Energy Storage System (38)

4.4.2. Operation of Battery Ultracapacitor Hybrid (40)

4.5. Modeling of High-rise Building Elevator (40)

vi

4.5.1. Elevator Model (41)

4.5.2. Powertrain Model (41)

4.5.3. Modeling of PEM Fuel Cell system (43)

4.5.4. Modeling of Motors (46)

4.5.5. Modeling of Energy Storage System (47)

4.6. Elevator Power Management (49)

4.7. Computer Simulation (51)

4.7.1. Elevator Traffic Patterns (Drive Cycles) (51)

4.7.2. Low Power Mode Simulation (52)

4.7.3. High Power Mode Simulation (55)

4.8. Optimal Battery and Ultracapacitor Units (57)

4.9. Cost Analysis (59)

4.9.1. Cost of PEM Fuel Cell System (59)

4.9.2. Costs of Batteries and Ultracapacitors (60)

4.9.3. Power Converter and Controller (60)

4.10. Discussion and Conclusions (61)

CHAPTER 5 Modeling of a ICE Hybrid Powertrain for Two-mode Hybrid Trucks Using ADVISOR (63)

5.1. Planetary Gear Based Power Transmission (63)

5.1.1. Speed, Torque and Power of the Planetary Gears (63)

5.1.2. Toyota Hybrid System (67)

5.1.3. The First Mode of a Two-mode Transmission (73)

5.1.4. The Second Mode of a Two-mode Transmission (78)

5.2. Vehicle Modeling in ADVISOR (84)

5.2.1. Modeling of Drivetrain (85)

5.2.2. Modeling of Engine (86)

5.2.3. Modeling of a Two-mode Transmission (88)

5.3. Control Strategy of a Two-mode Hybrid Vehicle (92)

5.3.1. Review on HEV Control Development (92)

5.3.2. Mode Selection (93)

5.3.3. Power Management of First Mode (94)

vii

5.3.4. Power Management of Second Mode (96)

5.4. Computer Simulation (97)

5.4.1. Drive Cycles (97)

5.4.2. Road Performance (99)

5.4.3. System Operation (102)

5.4.4. System Efficiency (104)

5.4.5. All Electric Range (108)

5.5. Conclusions (109)

CHAPTER 6 Modeling of ICE Hybrid Powertrain for a Parallel Hybrid Truck Using Modelica/Dymola and Validation (111)

6.1. Parallel Hybrid Electric Vehicle (111)

6.2. Vehicle Modeling in Dymola (112)

6.2.1. Engine Modeling (113)

6.2.2. Transmission Modeling (115)

6.2.3. Chassis and Resistance Modeling (116)

6.2.4. Driver Modeling (118)

6.3. Models Simulation and Validations (118)

6.3.1. Engine Model Validation (118)

6.3.2. Torque Converter Model Validation (119)

6.3.3. Transmission Model Validation (121)

6.3.4. Chassis and Resistance Model Validation (122)

6.4. Overview and Conclusions (123)

CHAPTER 7 Summary (124)

7.1. Research Problem (124)

7.2. Technology Review (124)

7.3. Vehicle Modeling (124)

7.4. Future Work (125)

REFERENCES (126)

viii

List of Figures

Figure 1-1 Globe Oil Consumption Perspective [4] (2)

Figure 1-2 Toyota Prius-Most Sold HEV (3)

Figure 1-3 a Series Hybrid Electric Vehicle Configuration (5)

Figure 1-4 a Fuel cell HEV Configuration (6)

Figure 1-5 a Pre-Transmission Parallel HEV Configuration (7)

Figure 1-6 a Post-Transmission Parallel HEV Configuration (7)

Figure 1-7 A All Wheel Drive Parallel HEV Configuration (8)

Figure 1-8 Toyota THS Configuration (10)

Figure 2-1 Power/Energy Ratio of Vehicle Demand and ESS Capability (15)

Figure 3-1 Flow Chart of an Backward Modeling Approach (26)

Figure 3-2 ADVISOR/Simulink Block Diagram of a Two-mode Truck (26)

Figure 3-3 ADVISOR Vehicle Input Interface (28)

Figure 3-4 Simulation Setup Interface (28)

Figure 3-5 Simulation Result Window (29)

Figure 4-2 a Fuel cells Super Hybrid Power System (39)

Figure 4-3 Physical Model of an Elevator (41)

Figure 4-4 Modeling a Fuel Cell Hybrid Vehicle/Elevator in ADVISOR (42)

Figure 4-5 A PEM Fuel Cells Stack (44)

Figure 4-6 a Fuel cell system Model in ADVISOR (45)

ix Figure 4-8 Motor Model Power Flow (46)

Figure 4-9 Motor Model in ADVISOR (46)

Figure 4-10 AC30 Motor Power Efficiency (47)

Figure 4-11 Energy Storage System Model (47)

Figure 4-12 Energy Storage System Model in ADVISOR (48)

Figure 4-13 Power Management System of a Fuel Cells Hybrid Powertrain (49)

Figure 4-14 Fuel cell system Power Management Flow Chart (50)

Figure 4-15 Simulation of Low Power Cycle (52)

Figure 4-16 System Power Demand-Low Power Cycle (53)

Figure 4-17 Fuel cells Power Demand-Low Power Cycle (53)

Figure 4-18 Battery SOC-Low Power Cycle (54)

Figure 4-19 Ultracapacitor SOC-Low Power Cycle (54)

Figure 4-20 Performance Simulation of High Power Cycle (55)

Figure 4-21 System Power Demand-High Power Cycle (55)

Figure 4-22 Fuel cells Power Demand-High Power Cycle (56)

Figure 4-23 Battery SOC-High Power Cycle (56)

Figure 4-24 Ultracapacitor SOC-High Power Cycle (57)

Figure 4-25 Optimal Battery Units (58)

Figure 4-26 Optimal Ultracapacitor Units (58)

Figure 5-1 A General Planetary Gear (64)

Figure 5-2 Power Flow Chart of Planetary Gear (67)

Figure 5-3 Toyota THS Configuration (68)

x Figure 5-4 Engine, M/G1 and M/G2 Speed of THS (69)

Figure 5-5 THS Power Flow Chart Engine Off (69)

Figure 5-6 THS Power Flow Chart Engine Start (70)

Figure 5-7 THS Power Flow Chart V1

Figure 5-9 First Mode Drivetrain Configuration (73)

Figure 5-10 Speed of Engine, M/G 1, M/G2 and Output Shaft (74)

Figure 5-11 First-mode Power Flow Chart-Engine Off (75)

Figure 5-12 Power Flow Chart of Forward Movement in the First Mode (76)

Figure 5-13 Power Flow Chart of Backward Movement in the First Mode (77)

Figure 5-14 Second Mode Drivetrain Configuration (78)

Figure 5-15 Power Flow of Second Mode at Vehicle Speed of Vs3 or Lower (80)

Figure 5-16 Power Flow of Second Mode during Brake at a Vehicle Speed of Vs3 or Lower (81)

Figure 5-17 Power Flow of Second Mode at a Vehicle Speed Greater than Vs3 82 Figure 5-18 Power Flow of Second Mode Brake at Speed over Vs3 (83)

Figure 5-19 Free Body Diagram of a Truck (85)

Figure 5-20 Engine Model Schematic Diagram (87)

Figure 5-21 Simulink Block Diagram of Engine Thermal and Fuel Model (88)

Figure 5-22 A Schematic Diagram of Two-mode HEV (88)

Figure 5-23 Two-mode Transmission Model and its Controller (91)

Figure 5-24 First Mode Block in Transmission Model (92)

Figure 5-25 Mode Switch Control (93)

xi Figure 5-26 Speed Profile of All Shafts (Engine Speed predefined) (94)

Figure 5-27 Power Management Chart Mode 1 (95)

Figure 5-28 Power Management Chart Mode 2 (96)

Figure 5-29 Vehicle Speed on the UDDSHEV Cycle (99)

Figure 5-30 Vehicle Speed on NYCTRUCK Cycle (100)

Figure 5-31 Vehicle Speed on CSHVR Cycle (101)

Figure 5-32 Vehicle Speed on HWFET Cycle (101)

Figure 5-33 Engine Power on NYCCTRUCK Cycle (102)

Figure 5-34 Electric Motors Power Demand over NYCCTRUCK Cycle (103)

Figure 5-35 Speed of Engine and Electric Motors on NYCTRUCK Cycle (103)

Figure 5-36 Battery SOC History on NYCTRUCK (104)

Figure 5-37 Efficiency of Two Mode HEV and Conventional ICE Vehicle on UDDSHEV Cycle (105)

Figure 5-38 Efficiency of Two Mode HEV and Conventional ICE Vehicle on NYCCTRUCK Cycle (106)

Figure 5-39 Efficiency of Two Mode HEV and Conventional ICE Vehicle on CSHVR Cycle (106)

Figure 5-40 Efficiency of Two Mode HEV and Conventional ICE Vehicle on HWFET Cycle (107)

Figure 5-41 Summery of Fuel Consumptions (107)

Figure 5-42 All Electric Mode Operation on NYCCTRUCK (108)

Figure 5-43 Battery SOC on NYCTRUCK at AEM (109)

Figure 6-1 a Post-Transmission Parallel HEV Configuration (112)

xii Figure 6-2 Forward Vehicle Modeling Algorithm in Dymola (113)

Figure 6-3 Engine Model in Dymola (114)

Figure 6-4 Base Engine Modeling (115)

Figure 6-5 Engine Speed Governor Modeling (115)

Figure 6-6 Transmission Model in Dymola (116)

Figure 6-7 Chassis Model in Dymola (117)

Figure 6-8 Vehicle Resistance Model (117)

Figure 6-9 Driver Model (118)

Figure 6-10 Engine Model Validation (119)

Figure 6-11 Torque Converter Validation - Output Torque (120)

Figure 6-12 Torque Converter Validation - Output Speed (121)

Figure 6-13 Transmission Model Validation - Output Speed (122)

Figure 6-14 Vehicle Chassis Model Validation - Vehicle Speed (123)

xiii

List of Tables

Table 1-1 An Incomplete List of HEV been developed at present (4)

Table 2-1 Characteristic of a Benchmark EV (16)

Table 2-2 ESS Sizing for a Benchmark EV (17)

Table 2-3 Specs of Ni-MH on a 2004 Toyota Prius [16] (17)

Table 2-4 ESS Sizing for a HEV (18)

Table 2-5 UC-battery Hybrid ESS for Prius (18)

Table 2-6 UC-battery Hybrid ESS for Prius (19)

Table 2-7 Battery Performance Characterizes for HEV and EV (21)

Table 3-1 Vehicle Modeling Packages in Modelica (33)

Table 4-1 Parameters of a Prototype Elevator (43)

Table 4-4 Power Source Unit Sizes on Initial Simulation Test (52)

Table 4-5 Specification of Optimized Powertrain (59)

Table 4-6 Specification of Battery Based Elevator Backup Power System (59)

Table 4-7 Overall System Cost Prediction (61)

Table 5-1 Engine and Motor Operating Condition of THS (72)

Table 5-3 Summery of Engine, M/G1 and M/G2 in First Mode (78)

Table 5-4 Power Flow Summery of First Mode (78)

Table 5-5 Summery of Engine, M/G1 and M/G2 in Second Mode (83)

Table 5-6 Power Flow Summery of Second Mode (84)

xiv Table 5-7 Modeling Parameters (86)

Table 5-8 Signal Interface Explanation of a Two-mode Transmission Model (91)

Table 5-9 ESS SOC Management (95)

Table 5-10 Simulation Vehicles Specification (97)

Table 6-1 Engine Model Input (119)

Table 6-2 Torque Converter Model Input (120)

Table 6-3 Transmission Input (121)

Table 6-4 Transmission Input (122)

xv

List of Abbreviations

Electric

Mode

AEM All

Range

Electric

AER All

BOP Balance of Plant

Transmission

CVT Continuous

Variable

of

Energy

DOE Department

Hybridization

of

DOH Degree

Electrical

Machine

EM

Systems

Storage

ESS Energy

Vehicle

EV

Electric

Vehicle

Electric

Hybrid

FCHEV

Fuel

Cell

GHG Green house Gasses

Interface

User

GUI Graphic

Vehicle(s)

Electric

HEV Hybrid

Engine(s)

Combustion

Internal

ICE

IESVic Institute for Integrated Energy Systems

Acid

Battery

L-A Lead

Li-ion Lithium-ion

M/G Motor/Generator

Battery

Hydride

Nickel

Ni-MH

Metal

NYCC New York City Cycle

Battery

Acid

SLA Sealed

Lead

of

Charge

SOC State

Hybrid

System

THS Toyota

Membrane

Exchange

PEM Proton

Flow

Factor

Power

PF

Electric

Vehicle

Hybrid

PHEV Plug-in

Devices

Split

PSD Power

Victoria

UVic University

of

xvi

Acknowledgements

I would like to first acknowledge and express my sincere thanks to my supervisor, Professor Zuomin Dong for the opportunity that he gave me to work on this highly promising and exciting research area. I would like to express my gratitude to Jeff Wishart and Adel Younis, both Ph.D. candidates in the research laboratory, and Dr. Jianxiong Liu for their encouragement and warm assistance on their respective expertise. I would also like to thank Matthew Guenther, a recent graduate from the laboratory, whose Master thesis on related topics has provided solid foundation for the initiation of my research.

Financial supports from the Natural Science and Engineering Research Council of Canada, University of Victoria, Azure Dynamic and MITACS program are gratefully acknowledged.

Finally, a special thank you goes to my parents Zhou Yong and Yu Dongmei for their moral and financial supports during my study in Canada.

CHAPTER 1Introduction

1.1.The Need of Hybrid Electric Vehicles

In recent years, a significant interest in hybrid electric vehicle (HEV) has arisen globally due to the pressing environmental concerns and skyrocketing price of oil. Representing a revolutionary change in vehicle design philosophy, hybrid vehicles surfaced in many different ways. However, they share the hybrid powertrain that combines multiple power sources of different nature, including conventional internal combustion engines (ICE), batteries, ultracapacitors, or hydrogen fuel cells (FC). These vehicles with onboard energy storage devices and electric drives allows braking power to be recovered and ensures the ICE to operate only in the most efficient mode, thus improving fuel economy and reducing pollutants. As a product of advanced design philosophy and component technology, the maturing and commercialization of HEV technologies demand extensive research and developments. This research intends to address many key issues in the development of HEV.

1.1.1.Environmental Concerns

The United Nations estimated that over 600 million people in urban area worldwide were exposed to traffic-generated air pollution [1]. Therefore, traffic related air pollution is drawing increasing concerns worldwide. Hybrid electric vehicles hold the potential to considerably reduce greenhouse gas (GHG) emission and other gas pollution. A fuel cell HEV, which only produce water and heat as emissions during operation, makes pollution more controllable by centralizing GHG emission and air pollution to the hydrogen production process at large scale manufacturing facilities. ICE based hybrids, on the other hand, can improve the fuel economy and reduce tailpipe emission by more efficient engine operation. The improvements come from regenerative braking, shutting down the ICE while stationary and allowing a smaller, more efficient engine which is not required to follow the power at the wheel as closely as the engine in

2 a conventional vehicle must [2]. In an emission effect comparison of the Toyota Prius (HEV) and Toyota Corolla, it was reported that the Prius only produced 71% of CO2, 4% of CO and 0.5% of NO x compared with the Toyota Corolla. The Corolla is one of most efficient conventional vehicles on the market.

1.1.

2.Energy Consumption

Around the world, we are experiencing a strong upward trend in oil demand and tight supply. Maintaining a secure energy supply becomes an on-going concern and a high priority. The US Department of Energy (DOE) states that over 15 million barrels of crude oil are being consumed in the nation of which 69% are for the transportation sector [3]. The transport energy consumption worldwide are also continue to rise rapidly. In 2000 it was 25% higher than in 1990 and it is projected to grow by 90% between 2000 and 2030 as shown in Figure 1-1.

Figure 1-1 Globe Oil Consumption Perspective [4]

Many HEV projects reported fuel economy improvement from 20% to 40% [5]. Therefore, HEV provides a promising solution to relieve the energy shortage.

3

1.1.3. Current Global HEV Market

In 1970s, many auto makers such as GM, Ford and Toyota started to develop electric vehicles powered by batteries due to the oil shortage. However, these electric vehicles powered solely by battery power did not go far enough. The interest in hydrogen fuel cell cars has arisen as a result to address the range problem associated with battery power cars. However, with more than 15 years of intensive development, there are still not any fuel cell hybrid cars on market mainly due to the high manufacturing cost. In the meantime, other automotive manufacturers have moved in another direction of ICE based HEV . In 1997, Toyota introduced the Prius (Figure 1-2), the first ICE based HEV to the Japanese market. Ever since, an increasing number of HEV have

become available.

Figure 1-2 Toyota Prius-Most Sold HEV

The sales of HEV are growing rapidly. An estimated 187,000 hybrids were sold in the first six months of 2007 in US, accounting for 2.3 percent of all new vehicle sales according to J.D. Power. J.D. Power also forecasted a total sale of 345,000 hybrids for 2007, a 35% increase from 2006.

1.2. HEV Classifications by Power Source

There are many ways to classify hybrid electric vehicles. One way is based on principal power sources. Two major principal power sources for HEV are ICE and fuel cell system.

4 Table 1-1 An Incomplete List of HEV been developed at present

Manufacturers and Vehicles Year Type

Toyota Prius, Camry, Highlander 1997 Sedan, SUV

Lexus RX400h, LS600H 2005 Sedan, SUV

SUV

Accord 2005 Sedan,

Civic,

Honda Insight,

GM Silverado, Saturn, Equinox, Tahoe, Yukon 2007 Truck, SUV

GM New Flyer 2004 Heavy Bus

Chrysler Durango, Ram 2005 Truck

Mercedes Benz S 2006 Sedan

Mariner 2005 SUV Ford Escape,

Hyundai, Renault, IVECO 2004 Various

1.2.1.Internal Combustion Engine Based HEV

In an ICE based HEV, the engine is coupled with electric machine(s). This modification creates integrated mechanical and electrical drive trains that merge power from both the ICE and the electric motors to drive the vehicle. By using the energy storage system as a power buffer, the ICE can be operated at its most efficient condition and reduced in size while maintaining the overall performance of the vehicle. In this type of vehicles, fossil fuel, however, is still the sole energy source to the vehicle system, (except for plug-in HEV where electricity obtained from electrical grid provides another power source). The charge of the battery is maintained by the ICE and the electric machines. As a consequence of the reduced engine size, more efficient engine operation, and recovered braking power, fuel usage and emissions of the vehicle are considerably lower than comparable conventional vehicles.

At present, all commercialized HEV are ICE based. Many possible mechanical configurations can be implemented for an ICE based HEV. More detailed vehicle configurations will be explained in Section 1.3.

1.2.2.Fuel cell Based HEV

A fuel cell hybrid electric vehicle operates solely on electric power. The fuel cells continuously

5 produce electrical power while energy storage devices buffer the power flow in the electric power train. A fuel cell system is an electric power-generating plant based on controlled electrochemical reactions of fuel and oxidant [6]. In principle, fuel cells are more efficient in energy conversion and produce zero emission. Due to many attractive features, such as low operation temperature, compact structure, fewer corrosion concerns, and quick start-up, the Proton Exchange Membrane (PEM) fuel cells serves as an ideal power plant for automotive applications.

1.3.HEV Classifications by Drivetrain Architectures

One of the most common ways to classify HEV is based on configuration of the vehicle drivetrain. In this section, three major hybrid vehicle architectures introduced are series, parallel and series-parallel. Until recently, many HEV in production are either series or parallel. In terms of mechanical structure, these two are primitive and relatively simple. A series-parallel powertrain brings in more degrees of freedom to vehicle engine operation with added system complexity.

1.3.1.Series Hybrid

One of the basic types of HEV is series hybrid. In this configuration, as shown in Figure 1-3, the ICE is used to generate electricity in a generator. Electric power produced by the generator goes to either the motor or energy storage systems (ESS). The hybrid power is summed at an electrical node, the motor.

Figure 1-3 a Series Hybrid Electric Vehicle Configuration

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