Felix Hoffmann, Marc Veigel, Martin Doppelbauer

2018 IEEE International Conference on Power Electronics, Drives and Energy Systems (PEDES)

Abstract

Encoders are one of the critical parts in an electric drive system. In safety critical applications like an air plane a redundant and robust sensor-less controller with an approval in aviation is required. This paper presents a hysteresis current controller, which is implemented on a FPGA. We simulated the switching action and the controller dynamics and measured it on a test bench. We describe the transients excited by the switching action analytically. Although transients are excited at the switching moment, a stable operation of the machine is ensured. The results of simulation and measurement of the switching action show a maximal deviation of 6% in the stator current amplitude. The excited transients describe a sinusoidal shape for the rotor speed. The analytical solution of the oscillation amplitude deviates from the measured results by a maximum of 14%. The oscillation frequency is 24% up to 35% smaller, depending on the operating point. The differences are due to the assumption of phase currents with a constant amplitude. It is shown that the dq-current components follow the constant torque hyperbola, if the current reference amplitude changes. In case of a load torque change they will move on the constant stator current circle and turning clockwise for a load torque decrease and counter clockwise for an increase. Due to the working principle of the controller, the current distortion is significant and is measured to 29% in a defined operating point. The measurement results validate the simulation results. The implemented hysteresis current controller can be used to improve the redundancy of a control structure.