Week-4 Challenge WOT Condition Part-2

1 : Most common difference between mapped and dynamic model of engine, motor and generator as per below.

Fig:1 Dynamic and Mapped model of engine

Fig:2 Mapped and Dynamic model of motor

Fig:3 Mapped and Dynamic model of Generator

→→ First basic difference should be that most probably Mapped has one block and Dynamic block has many.

→→ Mapped Model uses a set of steady-state lookup tables to characterize performance.

For the case of Engine : The tables provide overall engine characteristics, including actual torque, fuel flow rate, BSFC, and engine-out exhaust emissions.

For the case of Motor/Generator : Specify electrical torque range with a torque-speed envelope or maximum motor power and torque. Also Specify electrical losses as a single operating point that estimates loss across the operating range, measured loss, or measured efficiency.

→→ Dynamic Model decomposes the behavior of component characteristics that are separated into lower-level components. By combining components in this way, the models capture the dynamic effects.

For the case of Engine : We can see that dynamic blocks have required input. like, TrqCmd, EngSpd, etc data. So, to generate those input data we will use other blocks to generate data accordingly.

For the case of Motor/Generator : Also based on MotorTrqCmd, MotSpd, we have to generate MotTrq, MotCurnt. For that we have used 'Interior PM Controller SS Trq', 'Three-Phase Voltage Source Inverter', Interior PMSM SS Spd, type blocks.

→→ Basically, If we have engine data from a dynamometer, then we will directly apply that data in a 'mapped block'.

Otherwise we need to generate required data from other blocks.2 : From 'Variant subsystem', we can activate the choice.

If we have 'Hybrid electric vehicle (HEV) — Multimode', file then this path need to be followed,(reference photo attached)

HevMmReferenceApplication > Passenger Car > Electric Plant > Motor (Variant subsystem) > Right click > Variant > label mod active choice > select which to active.

Fig:4 Change Model Type

Ans B 1of2 : A gallon is a unit of measurement for liquids. In America, it is equal to about 3.785 litres. MPG, or miles per gallon, is the distance, measured in miles, that a car can travel per gallon of fuel. MPG is also the primary measurement of a car's fuel efficiency: The higher a car's MPG, the more fuel efficient it is.

Fig:5 US-MPGe curve of Full electric vehicle

In above fig. We can see the 'US-MPGe curve' of 'Full electric vehicle'. Let's see how it's generated.

It uses 'Vehicle speed' and 'Battery power' to generate curve.

Fig:6 Vehicle Body 3 DOF Longitudinal block

As per above path > "EvReferenceApplication/Passenger Car/Drivetrain (DrivetrainEv)/Vehicle" from 'Vehicle Body 3 DOF Longitudinal block' vehicle velocity(m/s) derived.

Fig:7 Battery Power (watts) calculation

And As per above path > "EvReferenceApplication/Passenger Car/Electric Plant" Battery Power (watts) calculated by multiplying 'Battery volte' and 'Battery current'.

Now Using 'Bus selector' all values that are going to visualize in the graph, such as 'vehicle velocity(xdot)', 'Motor speed(MotSpd)','Battery current(BattCrnt)' etc are extracted.

In the image below we can see how the 'Miles per gallon' calculated.

Fig:8 Miles per gallon calculation

First, Speed unit converted meter to miles.

Second Battery power, converted to 'kw' then 'kwh/US EPA equivalent' then 'per sec' and then 'm3 per gal'.

And then, using the 'product block' 'Miles per gallon' calculated.

Ans B 2of2 : 'US EPA equivalent' factors can be considered to model fuel flow. That converts KWH to 'kwh/USgal' .

One more factor can be considered to convert in m3/gal, multiplying by constant (0.00378541).

Ans C : Hybrid Electric Vehicle Multimode Reference Application with WOT drive cycle at different condition of Grade and Velocity as per below.

Fig:9 Powertrain configuration

As the name HAV suggests they have Engine + Electric Motor to power the Vehicle. This Reference application has Parallel arrangement to transmite the power, can be seen in Fig 9.

Fig:10 HEV with WOT drive cycle (grade - 0, wind_x - 0)

Here First we have simulated HEV on WOT with its default conditions. Where 0-5 sec idle, 5-80 sec with speed 50 m/s , after 80 sec going to start deceleration, then remain 0 m/s until 210sec. Let's understand the above curve.

As per the 'Battery SOC curve' we can see at initial level battery at 80%. it's controlled by 'Relay' block(SOC Controller Off/On) where Switch on Point "ChrgSOCHi" variable set at 80 & Switch off Point "ChrgSOCLo" variable set at 70.

As per the "RPM curve" we can see at initial level only the motor is started to power up the vehicle because of battery SOC at 80%. with time the battery SOC is going to discharge, and after 20 sec battery SOC going to below 70%. And at that point the same time Engine & Generator is started can be seen in "Torque curve".

As per the 'input velocity curve' it instantly increases 0 to 50 m/s. But as we can see, practically is that not possible, Velocity is increasing in a smooth radius. Here limiting factor is Battery output current(A). As per 'Current curve' we can see the max. current output is around 500 amp. After some time at around 44 sec the vehicle matched the top speed of input speed 112mph (~50m/s). Upto ~40 sec the vehicle maintaining its top speed. As here 'Parallel arrangement to transmite the power' so, motor rpm becomes high with the high speed of vehicle but due to engine runnig, torque is divided between motor and engine. That is why we can see battery current & motor torque reduced by about 65%.

After 80 sec, input speed is 0. Sp, vehicle is going down to 0. In 5 sec vehicle speed is becomes 0. Between 80-85 sec we can see the motor has a negative torque & current value, Because of at that time the motor is not giving any output but for a short period of time it works as a generator. This is the regenerative braking system concept.

Now, after 85 sec we can see the vehicle speed is 0 m/s but still the engine and generator is on. Because of battery SOC at 58% . And As per 'SOC Controller', it is trying to recharge the battery upto 80%. As we can see, around 180sec the battery is achiev 80% SOC. And then after 180 sec all component is turning off.

Fig:11 HEV with WOT drive cycle (grade - 5, wind_x - 0)

Fig:12 HEV with WOT drive cycle (grade - 0, wind_x - 10)

Fig:13 HEV with WOT drive cycle (grade - 5, wind_x - 10)

In Above example , Grade & Wind are acts as resistance. All component functions are acting normally in all different conditions. But the major difference we can see is that "time required by the vehicle to achieve the top speed. As per Fig 10 without any major resistance vehicle successfully achieved his speed in 75sec. But as per Fig 11,12,13 after applying grade and wind we can see differences to archive the inputs top speed. In 80 sec they failed to achieve the speed, they required some more time. By increasing battery current or engine power we can overcome this issue.

Ans D : Electric vehicle reference application with WOT drive cycle at 5 Grade and 10 m/s Velocity as per below.

Fig:14 EV with WOT drive cycle (grade - 5, wind_x - 10)

In EV we can see almost all performance is same. In HEV many variations we are getting in speed, Torque, Current. But In EV a smooth curve is generated. In HEV Max. battery current is around 450amp. But in this EV Max. Battery current is around 230 amp. Where torque is almost the same. So, Due to Battery current at some level it limits its overall performance. That's why EVs are getting 75mph max. speed upto 80 sec. So, overall a 5 mph speed difference.

Other is in HEV getting 55% battery SOC and in EV getting 73% battery SOC. That means HEV has lower KWh of battery and EV has higher KWh battery required.

4 . CONCLUSION :

From the this challenge I understand,

• What is Mapped and Dynamic Block, when and how to use it.
• What is a gallon and how are they calculated in EVs?
• And How the HEVs and EVs work at different conditions.