Control system of an e-vehicle propulsion drive

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Dr. Varjasi István
Department of Automation and Applied Informatics

My thesis is connecting to the BMEmotion project established by Budapest University of Technology and Economics. The scope of the project team was to design and build an electric racing car. The prototype of the future two permanent magnet synchronous machines, which planned to be built into the rear wheel hub created but the previous version of supplier voltage-fed inverter was not adequate to drive it.

Therefore, based on the measurement experiences, a brand new hardware was designed and manufactured. We also choosed a different microcontroller, which is optimised for electric drives.

In my BSc thesis, I implemented the field-oriented control software, which was tested in HIL (hardware-in-the-loop) simulator environment.

This thesis is beginned with the installation and test of the control hardware, aimed to test the software in real environment. In the introduction, I present the components of the inverter and outline that in which way is going to be connected to the other control electronics of the vehicle.

Given, that we are speaking about a 17 kW electric power converter, that will operate in a vehicle, the protections plays an extremely important role.

I will go in details in the field of the covered maulfunctions. I made sure, that the protections functions well by carrying out measurements.

In an electric propulsion system, several sensing functions can be find like current measurements, that are essential for the current control loop. Because of the field orientating, a rotation position detecting device also required. The sensorless methods work properly only on high rotor speed of a machine, that is why in vehicle drives mainly encoders used. It is also good to know the voltage of the DC bus, that helps to estimate the phase voltage applied on the motor. Furthermore, temperature measuerements can help, to prevent overheating.

After the setting up and the tests of the used sensors, the main circuit was successfully put into operation. Step by step, I performed the measurements working with another team member. After the successful initial tests, the driving system was able to drive our unique hub motor without loads.

In the other half of the semester, I worked on the perfection of the software, and as a result, a pole flux position estimator algorithm designed, and the driving system was modified to communicate with the vehicle controller, which will specify the torque reference for the three-phase voltage inverters. To test the communication, again I used the FPGA based HIL simulator platform.


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