Week-4 Challenge WOT Condition Part-2

QUESTION -

1. What is the difference between mapped and dynamic model of engine, motor and generator? How can you change model type?
2. How does the model calculate miles per gallon? Which factors are considered to model fuel flow?
3. Run the HEV ReferenceApplication with WOT drive cycle. Change the grade and wind velocity in the environment block. Comment on the results.
4. Keeping all other parameters same, compare the simulated results of hybrid and pure electric powertrains.

SOLUTION 1 -

Below model shows the Mapped and Dynamic model of MotGenEv.We get this model from the Powertrain Blockset in the MATLAB documentation.Open the EV referance model application.

In passenger car block there is a sub system in which there is Electric Plant and Drivetrain blocksets.Under the Electric plant block there is a subsytem called EV Mapped model.The EV Mapped model consists of both mapped MotGen model and Dynamic MotGen model.

Mapped Model of Motor -

1. The Mapped model is the model in which all the details or data related to motor are given in the form of look up tables. All the data related to the motor like motor torque, current, power are feeded in the lookup table.
2. The mapped model is also known as static model.
3. The simulation time of mapped model is much quick compared to dynamic model.
4. Mapped model consists of pre-defined datas in the look up table so that the mapped model works more quickly than Dynamic Model.

Below model is the sub system of the MotGenEvMapped block,

Dynamic Model of Motor -

1. The Dynamic model consists of real time components or the actual components of the motor. It contains real time data in the components so that the result is more accurate.
2. The Dynamic model consists of actual components like PM controllers, 3 Phase Voltage source inverter and 3 phase permanent magnet sychronous motor etc
3. The simulation time for the dynamic model is more as compared to mapped because it takes time to get the results based on real time situations.
4. Construction of Dynamic model is complex than that of Mapped model.

Below model shows the sub system of dynamic MotGenEv block,

To Change the model -

Following steps are carried out to change the model,

• Open the EV reference application model from the Matlab Help documentation.Then open the passenger Car block.
• The Passenger car block has sub system called Electric plant and inside Electric plant there will be MotGenEv block.
• Right click on the Motor block and choose the "Varient" option and it shows the Open option, open it.
• Then click on the model which is needed. Here we can change the model from Dynamic to Mapped and Vice versa.

Above Steps are easily understand by the below picture.

SOLUTION 2 -

To understand how the model calculates the miles per gallon in the HEV Reference application, we need to open the HEV Reference application from the Matlab Help documentation.In the HEV model there are several Powertrain blocksets in which we need to open the Visualization block.

In visualization block there will be several sub systems to get the desired output results.The Performance calculations block will have the blocks to calculate the miles per gallon which is shown in the below picture. Generally the miles per gallon refers to the Engine fuel consumption in the units of gallon.

The miles per gallon calculation requires 3 input values namely Vehicle speed, Battery power and Fuel flow.

The below picture shows the conversion of battery power into equivalent form of Gasoline density. The Fuel flow gets added up with Gasoline density then it is integrated and converted into Litres(L). Also the vehicle speed is integrated to get the distance and it is used further to get miles per gallon.

The distance in metre is converted into miles and the equivalent gasoline S.G in m^3 is converetd into US Gal. The distance in miles is divided by US Gal to get the Miles per gallons.

Factors considered in model fuel flow :-

1)Battery power Capacity should be high and vehicle power consumption should be low for higher MPGe (Miles Per Gallon equivalent).

2)vehicle speed

SOLUTION 3 -

HEV Referance Model -

The below picture shows the HEV model in which series parallel type of configuration is used.

Explanation -

Below HEV Reference Model is obtained from Matlab Help Documentation in the Powertrain Blockset.In HEV Reference application there will be several powertrain blocksets, Environment block and drive cycle blocks.

As mentioned in the challenge itself select the Wide Open Throttle(WOT) drive cycle and enter the reference speed, deceleration time and WOT simulation time according to user choice.There is no change takes place in the Grade and Wind Velocity block.These parameters are present in the Environment block.

The Controller block contain Powertrain control module(PCM), PCM input and PCM output block.These block contains different subsystems in it.The Passanger Car block contains Engine, Electric plant and Drivetrain Blocks.

The WOT cycle is running for 30 sec as shown in the above block of Drive cycle source, so that we select the simulation time as 50 sec.

Results -

In the below result the reference velocity and actual velocity is shown in which it takes 10.837 sec to reach the maximum speed of 67.11mph.

The Battery SOC is reduced from 80% to 74.5% due to WOT condition and then it reached to some constant value as shown in the below plot.

The battery current also get increases above 500 ampere then remain constant for some time and then it rapidly decreased as the motor torque decreased.

The Miles per gallon also gets increased due to use of engine power.

The Engine speed and Velocity graph shows the same behaviour but their values are different. Engine Torque is constant for some time i.e 300Nm then it is reduced.

Change in Grade and Wind Velocity -

In the Environment Block, We can change the values of Grade and Wind velocity. Here we considered Grade and Wind velocity as 1 as shown in below picture.

Results -

The maximum speed of the vehicle gets decreased and also acceleration time to achieve maximum speed gets increased.

The battery SOC gets decreased during acceleration.

The reduction in speed is due to the battery capacity or battery current is not sufficient to achieve the maximum speed.

At last, by comparing both it can be concluded that the HEV with grade and wind velocity requires more speed, torque and battery current to overcome the given environment condition. Also it requires more time as compaired to No Grade and Wind velocity Model.

SOLUTION 4 -

Pure EV Application model -

The below model shows the Pure EV application model in which only battery is used as source of the vehicle. Below picture shows, the blocks in the model in simple manner which understand easily.

Below picture shows the EV Referance Application model,

Results-

HEV Reference model -

The below model shows the HEV reference model in which battery and engine is used as a source of the vehicle. The battery and Engine is connected in series parallel type.

Below picture shows the HEV Referance Application model,

Results -

Comparison of Pure EV and HEV -

1. In Pure EV model the battery is the only source but in the HEV model there will be both battery and engine and generator for regenerative braking.
2. In pure EV model the Battery SOC is gradually decreasing but in the HEV model the Battery SOC gets decreased and increased due to regenerative braking.
3. In EV model SOC of battery can not be utilized within a particular limit but it is possible in HEV, we can set upper limit and lower limit, if the SOC is below the lower limit the the motor stops and engine is turned on and the battery gets charged.
4. If the SOC of battey is equal to upper limit then the engine turns off and the model runs on motor until the SOC decreases below the lower limit.
5. In the results the motor speed alone is available in EV but in case of HEV there will be engine speed, Motor speed and Generator speed.
6. In pure EV model battery alone will help to provide the required power to run the vehicle but in the case of the HEV the engine also provides the power if battery power is not enough for the required power by vehicle.
7. The motor speed (RPM) is high for HEV compared to EV.