Battery powered electric vehicle
Using only 4 components from the library we can build a battery powered electric vehicle and investigate the range and consumption of the vehicle.
We start with the battery that is selected from the library/electric/battery folder. This model contains a detailed dynamic battery model, but has a user interface with a minimum set of parameters, just enough to study the basic effects of a battery.
The battery model has two electrical connections on the right side. The top connection is for measuring the State of Charge [SoC] of the batery. This value changes ranges from [0..1] and indicates the amount of energy in the battery. The voltage level in the battery is depending on the SoC and can be entered as a parameter in the model.
Open the battery model witthe right mouse button and change the value of the maximum battery voltage. Since we are not using any DCDC converters in this tutorial we directly set the battery voltage to 600 volt. This value is appropriate for feeding the electric drive model.
The other parameters in the battery model are the internal resistance in [ohm], the initial SoC, which indicates how much the battery is charged/discharged when the simulation starts and finally the amount of energy stored in a fully loaded battery [SoC=1]. Here you can enter the value in kilowatt hour [kWh].
| Parameters(4) | Default | Remark |
| U[volt] | 600 | Nominal voltage (Soc=60%) (Default value = 200 volt) |
| inital_SoC[0..100] | 100 | Initial State of Charge SoC of the battery. Specify between 0 and 100 |
| Rinternal[ohm] | 10m | Internal series resistance |
| kWh | 25 | Total amount of energy that can be stored in the battery |
The model for the electrical drive is selected from the library/ElectricalMachine/System folder. It is a single model that incorporates the power electronics, the electrical machine as well as the basic control. The VariableSpeedDrive has two electrical connections on the left side that have to be connected to the battery terminals. On the right side the drive shaft from the electrical machine can directly be connected to the drive train. The node at the right bottom side of the model is the control signal for the variable speed drive and is the amount to torque the drive should produce.
| Parameters(7) | Default | Remark |
| Nmax | 9000 | Maximum speed [rpm] |
| ConstantPowerSpeedRange[1..10] | 3 | Constant power speed range defines the maximum speed of the motor for maximum output power. wmax=CPSR*wnom |
| Nnominal[rpm] | 3000 | Nominal angular speed [rpm] |
| VdcMinimum | 500 | Minimum DC voltage for which the variable Speed Drive will function |
| Efficiency[0..1] | 0.95 | |
| Inertia[Kgm2] | 100m | |
| Pmax | 40k | Maximum power [Watt] |
The Constant Power Speed Range [CPSR] can be set and is default set to 3. For speeds beyond CPSR*Nnominal, the maximum power is decreasing quadratically. Usually operation of the drive is limited to CPSR*Nnominal[rpm]
The maximum speed is limited by the parameter Nmax and serves mainly as a mechanical speed limit of the drive.
The parameter VdcMinimum defines the minimum voltage of the DC link on the terminals at the left side. If the DC link voltage drops below this voltage limit, the drive will stop operating. Take care that this value is specified according to the nominal operating DC link voltage.
Using the efficiency parameter, losses of the first order can be modeled. Please note that these loss estimation is very rough.
The internal inertia of the drive, being motor plus shaft is modeled by the parameter Inertia. Use a value that is in accordance with the size/power level of the drive. A rough approximation of 100m[kgm2] will give sufficient simulation results. The mass of the vehicle basically overrides this parameter completely
The maximum power the drive can develop, irrespective of its torque demand is limited by the parameter Pmax. The drive will try to generate the required amount of torque as demanded by the torque control input, but as soon as the speed of the drive exceeds Nnominal. it will only deliver the maximum power Pmax to the shaft, until the maximum speed Nmax is reached.
A gearbox is placed between the electrical machine and the power train of the vehicle. On average a gear ratio of 3 to 4 uis applied in electrical vehicles. Here we will choose a gear ratio of 4. Seklect the gear box from the Library/Mechanic/Automotive/gear folder.
Instead of specifying the gear ratio as a single parameter, we specify the number primary and secondary teeth. The ratio between these two numbers is the gear ratio.
The efficiency of the gear box can eb specified by a number in the range [0..1]. On average an efficiency of 95% to 98% is reasonable and, for example, 98% is modeled 0.98.
The inertia of the primary disk is modeled and directly couples to the drive shaft.
Finally the Nissan Leaf is selected from the
Library/Mechanics/Automotive/Vehicle/Cars folder using the left mouse button and connected to the gearbox. The right side terminal is used for showing the speed in a scope.
For the electric vehicle we are only interested in the speed of the vehicle. Therefore it is enough to simply add a scope to the model to view its speed in kilometers per hour. Select the scope at the left bottom of the Caspoc-window by first clicking the scope-button and secondly clicking the left mouse button in the schematic.
The scope is added to show the speed of the vehicle.
Add a second scope to view the State of charge [SoC] of the battery and connect it to the top terminal of the battery model.
A connection is made by simply clicking the starting node with the left mouse button, drag the mouse to the end node with the left mouse button down and release the left mouse button soon as the green flag is appearing saying [Release mouse button to connect to scope input]
After releasing the left mouse button, the connection is made from the top terminal of the battery to the first input of the scope
The vehicle should drive for 2500 seconds. We want to see how it is accelerating and we want to see the increase in speed over time, as well the State of Charge of the battery. From the menu we select the simulation parameters dialog box.
In the simulation parameter dialog box we set the total simulation time and the step size for the simulation. Everything else can remain unchanged.
Set the simulation time to 2500 seconds and enter 1 for the step size.
Start the simulation by selecting Simulation/Start Simulation from the menu.
Scope1 shows the speed of the vehicle, while scope2 shows the State of Charge of the battery. After around 2000 seconds of drving, the battery is exhausted and the SoC dropped to zero. The same for the vehicle speed.
Since the scope windows are very small, we will enlarge them to get a better view of the simulation results during the simulation. To do this, we drag with the left mouse button pressed down the right bottom corner of the scope and resize it. If the scope is showing more inputs than connected, just leave them open. They will disappear when we restart the simulation.
We place the second scope right above scope1 to compare both signals during the simulation. Resize the scope by dragging the right bottom corner.
Connect the battery SoC terminal to the scope by simply clicking the starting node with the left mouse button, drag the mouse to the end node with the left mouse button down and release the left mouse button soon as the green flag is appearing saying [Release mouse button to connect to scope input]
