Control of AC machines and static converters for EV powertrains

The first area of the Chair focuses on robust sensorless control of electric drive motors. There are three different parts: position sensor control, torque monitoring, and PWM optimization control of AC machines inverters.

Part 1: Control of AC machines for EV without position/speed sensors

The main goals focus on the development and design of the new self-sensing control strategy for AC machines based on advanced estimation techniques to increase the performance, reliability, robustness of the control chain and reduce risk, cost and implementation complexity.

In the domain of classical (FOC, Feedback militarization, ...) and modern (sliding modes, backstepping, high gain, passivity, ... etc) controls of AC machines making the propulsion/traction of HEV/EV, the knowledge of rotor position and speed (figure 1) are required, which are obtained generally by a physical sensor (encoder or resolver). However, mechanical sensors are expensive, bulky, sensitive to the environment (temperature, noise, mechanical oscillations, electromagnetic compatibility, etc.) and reduce the system reliability. The mechanical sensor can be a sign of defects that can lead to the total loss of information or its degradation, resulting in a significant drop in performance and a malfunction of the traction chain. The position/speed estimation (figure 2) by means observers, or estimators, or generally speaking software sensors, becomes an ongoing need on the first part of the Chair Area 1, namely within EV and HEV, either for fault diagnosis and safety applications, or for the closed-loop self-sensing control. The main goal of software sensors is to estimate the position/speed by using only currents measurements of AC machines.

Figure 1: Control principle of AC machines with position/speed measurement


Figure 2: Control principle of AC machines without position/speed measurement (using observers, i.e. software sensors)

Part 2: Online monitoring of AC machine torque

AC machines like for example surface and interior permanent magnet synchronous machines (SPMSM, IPMSM) are widely used in EV/HEV applications because of their simplicity, reliability and robustness. Online monitoring of machine torque is a mandatory for an EV/HEV for reasons such as safety or/and control. Torque-meters (figure 1) removing in these applications and replacing them with a torque estimator (figure 2) based on measured/available signals such as voltages, currents and rotor position can make the drive system more reliable at less cost. Therefore, designing torque estimators for electric drives is the second part of the Chair Area 1.
 

Part 3: PWM control optimization for HEV/EV

Power Electronic Converters are widely used in electric vehicle (EV) and hybrid EV (HEV) powertrains. As the automotive application requirements are pushing the limits of the electrical components (higher power density, cost reduction, noise/vibration reduction, etc.), the control algorithms of the power converters are being challenged on several aspects, including the Pulse-Width Modulation (PWM) optimization. This part deals with the optimization of the PWM strategies of the two main power converters in an electric powertrain: the traction motor voltage source inverter (figure 3), and the battery charger (bidirectional rectifier).