Integrated Powertrain Simulation for Energy Management of Hybrid Electric Vehicles

Integrated Powertrain Simulation for Energy Management of Hybrid Electric Vehicles October 24 th, 2011 Kentaro Watanabe Nissan Motor Co., Ltd. 1

Outline 1. Motivation 2. Simulation technology 3. Recent achievements with this technology 4. Future direction 5. Summary 2

Outline 1. Motivation 2. Simulation technology 3. Recent achievements with this technology 4. Future direction 5. Summary 3

Motivation Strong demand for better fuel economy HEV is an effective and practical solution. Higher design flexibility Hybrid system and its control are complex and thus must be flexible in design. Better F.E. and development work efficiency System concept should be determined in the early stage of development Total vehicle system simulation! 4

Outline 1. Motivation 2. Simulation technology 3. Recent achievements with this technology 4. Future direction 5. Summary 5

Key technologies Vehicle energy management Effective use of electric/fuel energy Cooling of high-voltage system Making the most of the electric drive potential. 6

Flows of energy considered Kinetic, electric and thermal energies are considered. High-voltage battery Radiator Inverter Kinetic energy Electric energy Thermal energy Control signals ICE Clutch E-motor/ generator Clutch Transmission Vehicle body Radiator Hybrid controller Oil cooler 7

Fundamental HEV models All the basic models were prepared on GT-SUITE. Vehicle Topologies Cooling Systems Controllers - Battery EV - Power split -Series -Parallel - Series-Paralle Cooling system of -Engine - Transmission -High-Voltage -Battery SOC -Regenerative Braking -Hybrid mode switch 8

Online GT-SUITE Model Library - All the models, together with vehicle specifications, are available online. - Easy to build a vehicle model by combining models from the library. In-house Database Topologies (GT models) Vehicle Components Controllers (GT models) -Series - Parallel - Power split etc. - Vehicle mass - Vehicle Cd*A - Motor efficiency - Engine BSFC - TM efficiency - Auxiliaries loads etc. - SOC management - Regenerative braking - Series/parallel switch etc. 9

Cooling of high-voltage system Thermal loss from the components is defined as a function of the operating commands issued by the hybrid controller. Hybrid controller Converter Inverter control signals heat flow coolant flow heat source E-motor Modeling Water pump Coolant circuit Radiator Atmosphere 10

E-motor thermal model E-motor is discretized into several thermal masses to describe the temperature of each part. thermal mass thermal conductance Coil Copper Loss Insulator Modeling Stator core Iron Loss Housing 11

E-motor and cooling system model E-motor thermal model and component cooling models are integrated. Heat from adjacent components is applied. Transmission Case Inverter Heat from Transmission E-motor Coil Stator Core Insulator Radiator Water Pump 12

Outline 1. Motivation 2. Simulation technology 3. Recent achievements with this technology 4. Future direction 5. Summary 13

Plug-in Hybrid Concept ZEV & HEV in one car. Short weekday trips: EV (1) 2 drive modes - EV for short trips - HEV for long trips Charge every day (2)2/3 of annual mileage is covered by EV mode. HEV mode when high performance is required. HEV mode when battery is empty. Long holidary trips: HEV 14

Specifications of hybrid components Parallel HEV Battery Clutch ICE Transmission E-motor E-motor max. power ICE max. power Battery capacity Hybrid topology 60 kw 100 kw 10 kwh Parallel 15

Outline 1. Motivation 2. Simulation technology 3. Recent Achievements with this Technology - E-motor temp. control in high-load driving - Engine warm-up for improving cold start F.E. 4. Future direction 5. Summary 16

E-motor temp. in all-electric drive E-motor temperature increases markedly in high-load driving cycles. Vehicle speed [km/h] Power [kw] Coil temp. [deg. C] 150 100 50 0 60 40 20 0-20 -40 NEDC x 2 cycles Max. allowable temp. Lower than criterion OK 150 100 50 0 60 40 20 0-20 -40 Artemis Road x 2 cycles Exceeds criterion e-motor will be damaged. 17 0 500 1000 1500 2000 2500 0 500 1000 1500 2000 2500 Time [s] Time [s]

Hybrid drive under high coil temp. Using the hybrid mode can reduce the maximum coil temperature, but CO2 emissions increase. Artemis Road x 2 cycles 18 Coil temp. [deg. C] Power [kw] 60 40 20 0-20 -40 1000 1500 Max. allowable temp. Hybrid 0 500 1000 1500 2000 Time [s] Hybrid Hybrid ICE E-motor CO2 emissions [kg] All electric +13% Coil temp. unacceptable Fuel Electricity Hybrid Coil temp. OK

Outline 1. Motivation 2. Simulation technology 3. Recent Achievements with this Technology - E-motor temp. control in high-load driving - Engine warm-up for improving cold start F.E. 4. Future direction 5. Summary 19

Calculation Conditions (1/2) 5 cycles of UDDS, Start driving at 95% SOC 1)For cases without engine warm-up operation, Start in EV mode, switch to hybrid when SOC hits 25%. 2)For cases with engine warm-up operation, Start in hybrid mode until coolant temp. hits 80 deg. C. 95% 1st 2nd 3rd SOC 4th 5th 25% Vehicle speed Engine fuel consumption Hybrid EV mode Hybrid mode Time 20

Calculation Conditions (2/2) 3)For cases with exhaust heat recovery, 20% of exhaust gas internal energy at the catalyst outlet is applied to the engine coolant. Effect of exhaust heat recovery on warm-up speed and F.E.? 20% of internal energy ICE coolant T/M oil Catalyst Case A1 A2 A3 B1 B2 B3 Ambient temp. Engine warm-up Exhaust heat recovery -20 deg. C 0 deg. C 21

Warm-up speed Exhaust heat recovery shortens the warm-up time. This also quickens the start of cabin heating. Vehicle speed [km/h] Engine coolant temp. [deg. C] 22 90 60 30 0 100 80 60 40 20 0-20 -40 4.4 min shorter (ambient temp.=-20deg. C) Exhaust heat recovery ICE warm-up operation 0 1372 2744 4116 5488 6860 Time [s]

Reduction of CO2 emissions Exhaust heat recovery reduces CO2 emissions because of the reduction of engine/transmission mechanical losses. CO2 emissions for 5 cycles of UDDS [kg] -1.5% -0.1% w/o EHR w/ EHR Ambient temp. -20 deg. C Ambient temp. 0 deg. C 23

Outline 1. Motivation 2. Simulation technology 3. Recent Achievements with this Technology 4. Future direction 5. Summary 24

Future direction Extension of physical models for comprehensive optimization of vehicle systems Emissions and after-treatment treatment Sophisticated hybrid control High-voltage system cooling circuit Air conditioning - Battery thermal management - Battery deterioration 25

Future direction - Real-time simulation in HILS - As a tool to enhance collaboration between OEM and suppliers in powertrain system design Planning/Design Calibration/Validation Collaboration with Suppliers Target Definition Concept OEM Fleet Tests In-vehicle Test System Design Powertrain Test Component Design Component Test Collaboration with Suppliers SILS Development/Implementation HILS 26

Outline 1. Motivation 2. Simulation technology 3. Recent Achievements with this Technology 4. Future direction 5. Summary 27

Summary Developed a simulation model for total energy management, including thermal energy in HEVs. Presented applications for e-motor temperature control and powertrain warm-up strategy. These achievements showed that GT-SUITE is a powerful tool for HEV system design. Extension of physical models and speeding-up of simulations are both important. Use of common simulation platforms will be important for close teamwork between OEMs and suppliers in the auto industry. 28