Aim:
To model the pure electric vehicle and hybrid electric vehicle using Powertrain Blockset and compare their results for Wide open Throttle condition.
Introduction:
Powertrain Blockset:
<!--[if gte mso 9]><xml>· Powertrain Blockset provides fully assembled reference application models of automotive powertrains, including gasoline, diesel, hybrid, and electric systems.
· It includes a component library for simulating engine subsystems, transmission assemblies, traction motors, battery packs, and controller models.
· Powertrain Blockset also includes a dynamometer model for virtual testing. MDF file support provides a standards-based interface to calibration tools for data import.
· Powertrain Blockset provides a standard model architecture that can be reused throughout the development process.
· You can use it for design trade-off analysis and component sizing, control parameter optimization, and hardware-in-the-loop testing.
What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type?
Mapped Model:
- Model uses a set of steady-state lookup tables to characterize engine performance.
- The tables provide overall engine characteristics, including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions.
- We can use them when we have engine data from a dynamometer or a design tool like GT-POWER and for quasi steady-state engine simulations.
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Dynamic Model:
Model decomposes the engine behaviour into engine characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects.
We can use them when we need a more detailed dynamic model and have component-level data and to analyse the impact of individual engine components on the overall performance.
How does the model calculate miles per gallon? Which factors are considered to model fuel flow?
Miles per gallon (MPG) is a fuel economy rating determined by how far a car can travel on a gallon of gasoline or diesel.
Fig: calculation of MPG
factors are considered to model fuel flow
- Battery Power
- Fuel Flow
- Vehicle Speed
1.Battery Power:
Battery Power is indicated in W. To convert it to kW divide it by 1000.
1 US gallon of fuel = 33.7 kWh. divide it by 3600 to convert it to kW.
Multiply it by 0.00378541 to convert it into m^3/gal.Add gain of 739 to convert it into kg/m^3.
2.Fuel Flow:
Fuel Flow is in kg/s, it is integrated further to get quantity into kg.
Gain of 1/1000*739 is added to get kg into m^3. Add the gain of 1000 to convert m^3 into L.
3.Vehicle Speed:
Vehicle Speed is in m/s.it is converted into Root Mean Square velocity and integrated it with respect to time to get distance in m.
Divide it by 1000 to get fuel economy in terms of L/100km.
Gain of 0.0006213 is added to convert distance into miles to get fuel economy in terms of miles per gallon.
Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
Hybrid electric vehicle
- A hybrid electric vehicle(HEV) is a type of hybrid vehicle that combines a conventional internal combustion engine (ICE) system with an electric propulsion system.
- The presence of the electric powertrain is intended to achieve either better fuel economythan a conventional vehicle or better performance.
- Hybrid electric vehicles can be classified according to the way in which power is supplied to the drivetrain:
- In parallel hybrid, the ICE and the electric motor are both connected to the mechanical transmission and can simultaneously transmit power to drive the wheels, usually through a conventional transmission.
- In series hybrid, only the electric motor drives the drivetrain, and a smaller ICE works as a generator to power the electric motor or to recharge the batteries.
- Power split hybrid have the benefits of a combination of series and parallel characteristics. As a result, they are more efficient overall, because series hybrids tend to be more efficient at lower speeds and parallel tend to be more efficient at high speeds.
Fig: Powertrain configuration of HEV
Total simulation time: 100 s.
Nominal Refference Speed: 50 mph
Time to start decceleration: 60 s
Grade angle:0
Wind Velocity:0 m/s
Total 6 graphs are plotted with the required quantity on y axis and time on x axis.
We can use curser to check the value on two different points.
Plot 1:
Plot 1 shows the graph of Trace velocity in mph with respect to time.
Time to reach top speed of 112 mph = 40.98 s
Time to deccelerate = 5.96 s
Plot 2:
Plot 2 shows the graph of Battery current in Ampere with respect to varrious accelearation possition.
Peak battery discharge current = 165.95 A
Peak battery charging current = -140.54 A.
Plot 3:
Plot 3 shows the graph of Eng speed,Motor speed,Gen Speed in Rpm with respect to varrious accelearation possition.
Peak Engine Speed = 4765 RPM
Peak Motor Speed =13210 RPM
Peak Generator Speed =13440 RPM
Plot 4:
Plot 4 shows the graph of Battery SoC in % with respect to varrious accelearation possition.
plot shows depletion in Soc from 60% to 31.85 % in 41.027 s.
Plot 5:
Plot 5 shows the graph of Eng torque,Motor torque,Gen torque in Nm with respect to varrious accelearation possition.
Peak Engine torque = 146.63 Nm
Peak Motor torque =185.39 Nm
Peak Generator torque = 51.07 Nm
Plot 6:
Plot 5 shows the graph of fuel economy in miles per gallons.
maximum miles covered in a gallon of fuel = 15.65
Case 2:
Total simulation time: 100 s.
Nominal Refference Speed: 50 mph
Time to start decceleration: 60 s
Grade angle:7
Wind Velocity:10 m/s
Fig: add grade angle and wind speed
Fig: Simulation result
In case 2, we have added grade angle and wind velocity in the environment block.
Impact of grade angle and wind velocity can be seen in above 6 plots.
Plot 1:
Plot 1 shows the graph of Trace velocity in mph with respect to time.
Time to reach top speed of 70.59 mph = 59.98 s
Time to deccelerate = 3.42 s
Plot 2:
Plot 2 shows the graph of Battery current in Ampere with respect to varrious accelearation possition.
Peak battery discharge current = 168.63 A
Peak battery charging current = -143.41 A.
Plot 3:
Plot 3 shows the graph of Eng speed,Motor speed,Gen Speed in Rpm with respect to varrious accelearation possition.
Peak Engine Speed = 4650 RPM
Peak Motor Speed = 8628 RPM
Peak Generator Speed = 13890 RPM
Plot 4:
Plot 4 shows the graph of Battery SoC in % with respect to varrious accelearation possition.
plot shows depletion in Soc from 60% to 20.38% in 60.068 s.
Plot 5:
Plot 5 shows the graph of Eng torque,Motor torque,Gen torque in Nm with respect to varrious accelearation possition.
Peak Engine torque = 144.32 Nm
Peak Motor torque =201.119 Nm
Peak Generator torque = 52.58Nm
Plot 6:
Plot 5 shows the graph of fuel economy in miles per gallons.
maximum miles covered in a gallon of fuel = 9.86
Result:
- With the addition of grade angle and wind speed vehicle cannot reach to top speed of 112 mph.
- Vehicle is consuming more battery power due to the addition of wind resistance.
- Fuel economy is almost half after adding wind resistance.
Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains.
Electric
vehicle:
- An electric vehicle (EV) is a Vehicle that uses one or more electric motor or traction motor for propulsion.
- EVs convert over 59-62% of grid energy to the wheels. Conventional gasoline vehicles convert only some 17%–21%.
Fig: Simulation result
Plot 1:
Plot 1 shows the graph of Trace velocity in mph with respect to time.
Time to reach top speed of 70.76 mph = 59.98 s
Time to deccelerate = 4.14 s
Plot 2:
Plot 2 shows the graph of Battery current in Ampere with respect to varrious accelearation possition.
Peak battery discharge current = 299.89 A
Peak battery charging current = -7.7 A.
Plot 3:
Plot 3 shows the graph of Eng speed,Motor speed,Gen Speed in Rpm with respect to varrious accelearation possition.
Peak Motor Speed = 6992 RPM
Plot 4:
Plot 4 shows the graph of Battery SoC in % with respect to varrious accelearation possition.
plot shows depletion in Soc from 100 to 97.35% in 60.26 s.
Plot 5:
Plot 5 shows the graph of Eng torque,Motor torque,Gen torque in Nm with respect to varrious accelearation possition.
Peak Motor torque =120 Nm
Plot 6:
Plot 5 shows the graph of fuel economy in miles per gallons.
maximum miles covered in a gallon of fuel = 29.32
Comparison of the simulated results of hybrid and pure electric powertrains:
- HEV produces more torque when we combine both its engine and motor speed.Hence it can reach higher speed as compare to Ev.
- As Pure Electric vehicle use Lithium-ion battery,its rate of charging and capacity of discharging is higher than that of HEV which used Nickel metal hydrate battery.
- From depletion of SOC % to reach top speed, we can say that battery efficiency of pure EV is higher than HEV.
- EV's are more Fuel efficient than HEV's which can be seen from the plot of fuel economy in terms of miles per gallon.