STUDY OF EV AND HEV VEHICLE
AIM:
1. To study the mapped and dynamic model of the vehicle.
2. To study the conversion of gallon.
3. To study the WOT drive cycle used in HEV.
4. To study the comparison of HEV and EV powertrains.
KEYWORDS: Mapped motor, Gallon, WOT, HEV powertrains
SOFTWARE: Matlab, Simulink, Excel
OBJECTIVE:
1. To study the difference between the mapped model and dynamic model for engine, motor, and generator.
2. Calculating the capacity of tank / battery with speed to miles per gallon.
3. By using WOT drive cycle, Simulate the HEV reference model and change the grade and wind velocity parameters.
4. Study the Hybrid electric vehicle and pure electric vehicle.
Introduction: In this study, the model used for reference as Pure Electric Vehicle. It consists of Battery, motor, Gear, Differential and wheels with disc brakes. The battery and motor are connected electrically and other parts are mechanically connected. The motor used as Permanent magnet synchronous motor which produces emf by rotating only coil and fixed magnet which inturn produces torque and power sends to differential through transmission inorder to transfer the speed equally to the wheels. The battery used as Lithium ion battery which as more specific power, specific energy, low discharge rate, and more efficiency than lead acid battery.
In the Simulink model the motor has 2 kind, Mapped motor and Dynamic motor.
Mapped Model:
It uses a set of steady state lookup tabels to characterize motor / engine / generator performance.
The tables provide overall engine / motor / battery characteristics, including actual torque , motor speed, state of charge / discharge , flow rate, BSFC and emissions.
It is useful when we have noted datas of engine / motor / battery / generator or a design tool from GT power can simulate faster than the dynamic model. It is more useful for quasi steady state simulations.
It takes less time for simulation and details wrt to the lookup tabel.
Dynamic Model:
Model decomposes the engine / motor / battery / generator behavior into its particular characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects.
It gives detailed analyse and over all performance of Engine / motor / battery / generator.
It takes more time for simulation which captures the each and every component level data of Engine / Motor / battery / generator behaviour.
Subsystem of Dynamic Model:
The above subsystem consists of permanent magnet synchronous motor (PMSM) DC motor which is connected to the 3-phase which as three-phase electric power systems have at least three conductors carrying alternating current voltages that are offset in time by one-third of the period. 3-phase is used to high voltage from the battery.
To convert the model from mapped to dynamic or vice-versa,
- Select and right click the model and convert to variant subsystem.
- Goto variant manager and right click the model and active.
Study 2:-
1 Gallon of gasoline = 33.7 kWh
1 Gallon = 3.785 liter
1 Gallon = 0.003785 meter cube
1 meter cube = 264.2 US Gallon
1 meter = 6.215e-4
Battery output power and Vehicle speed are considered to model fuel flow, by converting the battery power in kW to Gallon and by converting vehicle speed interms of miles. It also defines the batery capacity per charge i.e., how much kilometer the vehicle can travel per charge. The miles per gallon (MPG) distance (in miles) a vehicle can travel on one gallon of fuel. For vehicle that operate on fuels that cannot be measured in gallons, the gasoline gallon is employed to give a reference point for comparison.
Study 3:-
A power-split hybrid electric vehicle (HEV) combines the advantages of both series and parallel hybrid vehicle architectures by utilizing a planetary gear set to split and combine the power produced by electric machines and a combustion engine. The main effects of power split mode is,
- Smaller electric machine peak power and sizes, especially for large vehicles
- Addition of clutches to transmission increases spin and pump losses
- ICE may not be at its optimum point during the fixed gear mode
- Higher tractive capability during fixed gear model
A planetary gearbox is a gearbox with the input shaft and the output shaft aligned. A planetary gearbox is used to transfer the largest torque in the most compact form (known as torque density). Inside, you have a sun gear that has a fixed point in the center and a planet gear (or gears) that rotate about the sun gear. As they rotate inside of the ring gear, the planetary gears create pitch circles that can be formed into a gear train that, in turn, is hooked up to input and output shafts.
The above results shows for 0 grade and 0 wind speed. The battery used as Nickel-metal hybrid battery. A nickel metal hydride battery, abbreviated NiMH or Ni–MH, is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide (NiOOH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and its energy density can approach that of a lithium-ion battery. Here, mapped motor and mapped generator are used and the simulation time taken as less. The battery was charged 60% and varying according to the the speed.
By changing grade angle as 15 degree and wind velocity as 10 mph in x-direction,
The above figure shows that, the actual velocity is decreases at an angle of 15 degree slope which needs more motor speed inorder to maintain the same speed and also withstand the wind velocity. The state of charge is decreasing during slope when compare to the 0 grade. The power required from the battery and ic engine is more during slope than the normal road. The maximum velocity reached as 41 mph.
A comparison with the logarithmic wind profile, the model is given by
where,
href it is a reference altitude
h0 is the wind profile starting altitude
Wref is the wind speed at the reference altitude
Lift depends on the square of the airspeed. So, as the airspeed decreases, the energy-extraction decreases with the square of the airspeed difference, which needs to be compensated with increasing wind speed. The evolution of energy gains and losses, for different steepness k of the wind profile is almost negligible.
The force of the wind is manifested principally in the load that is placed on the engine, a head wind requires greater power from the engine to maintain the same speed and tail wind requires less power. As the wind speed increases, the change in weight distribution also affects the car power. As raise in wind speed, the car causes lifting which reduces the traction power on the front wheels and reduces the weight distribution on the front to rear wheels.
Study 4:-
By comparing Hybrid Electric Vehicle and Pure Electric Vehicle, the parameters are defined as 15 degree grade angle, 10 mph wind velocity in x-direction and other parameters are same. Mass of the both vehicles are 1500 kg and vehicle total tractive force as 10 kN. The drive cycle used as Wide Open Throttle (WOT) for 40 secs and the battery used for EV as Lithium ion battery and for HEV Nickel-metal hybride (Ni-MH) battery. The capacity of battery is 80% and 60% respectively. When a vehicle driving during slope, the power requirement is more and discharge of battery is faster.
( i ) EV Simulation:
The results shows that, the maximum velocity attained as 18mph in 50 sec and the discharge of battery starts from 80% to 77%.
The figure shows that, the variation of torque and current over the speed.
( ii ) HEV Simulation:
The results shows that, the maximum velocity attained as 41mph in 50 sec and the discharge of battery starts from 60% to 35%.
OUTPUT:
( i ) Power losses for EV vehicle:
( ii ) Power losses for HEV vehicle:
( iii ) Drivetrain losses for EV vehicle:
( iv ) Drivetrain losses for HEV vehicle:
CONCLUSION:
1. The power loss in EV vehicle is less than the HEV vehicle, in this case the EV vehicle is more efficient than the HEV vehicle. Because the battery used for EV as Lithium ion which has low discharge rate than the battery used for HEV Nickel Metal hybrid (Ni-MH) battery.
2. The Drivetrain loss for EV as more than the HEV vehicle. The drive train used for HEV as planetary gear which is more feasible than other power train system. HEV consists of IC Engine part and also Battery part, it is also known as Full Hybrid Vehicle.
3. When a vehicle travels in slope, the power required is more than the normal road. Which causes more tractive force and also change in weight distribution due to wind velocity towards the vehicle.
4. All the cases are simulated in Mapped Motor / Generator due to shortage of time.