Power consumption of a battery powered electric vehicle

The simulation model from the previous tutorial is extended with sensors to measure the power consumption of the eVehicle. Also the Torque-Speed diagram of the eVehicle is created that shows the maximum torque produced by the eVehicle.

Continue from the previous tutorial and make some room between the components where you want to add the sensors. We want to measure the consumption and ls get a Torque-speed characteristic.
Select the WattDC from the Library/Sensor/Electrical folder and a PowerTorque component from the Library/Sensor/Rotational library.

Connect all components and add a scope to measure the vehicle speed.

To see the torque-speed characteristic, we add a scope, where on the x-axis the electric drive shaft speed is displayed and on the Y-axis the torque produced by the electric drive.

Open the scope for displaying the torque-speed characteristic using the right mouse button and select the XY-View in the menu.

Add two more scopes for displaying hte power consumption and State of Charge.
To display those signals, first label the nodes by clicking the node with the right mouse button and type the label. Do this for the node SoC, Pe and Pm.
Click with the left mouse button on the input of the scope and drag it to the left. A short line wil be created, where you can type the same labels.

The simulation shows the power consumption, which is nearly constant thanks to the Variable Speed Drive component. There is however one caveat, the mechanical power from the variable speed drive seems very small compared to the electric power. This is because this signal Pm is exported in kW instead of watt. We need to multiply that signal with 1000 before we can compare it with the electrical power consumption.

All we have to do for comparison is to multiply the signal with 1000. Select a GAIN block from the block/Math section, place it behind the sensor, click it with the right mouse button to open it and change its parameter to 1000. Change the label at the scope input to, for example, PmWatt and also change the label at the output of the Gain block to that value.

As you can see in the simulation results, the input electrical power is slightly higher than the mechanical power. This is because we defined the efficiency of the variable Speed Drive to be equal to 95%.

Also interesting is the DC link voltage as function of the State of Charge. We assume a constant voltage, but he battery voltage drops with decreasing SoC. We can graph this if we plot the SoC on the X-axis and the DC link voltage on the Y-axis of a scope. In order to be sure and measure the correct voltage with a single line, we simply ground the negative DC link rail and measure the positive rail voltage. This is done by adding a ground component that can be selected from the folder library/electric/ground. Don't forget to change the scope to XY plot by selecting View/XY-Writer in the menu in the scope.

We specified a nominal voltage of 600 volts. This will be the voltage when the State of Charge is 60%.

The amount of energy we used for driving is measured by the electric power sensor. Move the mouse pointer over the nodes and it will display numerically the result. Around 23 kWh is used which closely resembles the specified battery energy density of 25kWh.