A practical approach to HFI based sensorless control of PM-assisted synchronous reluctance machines applied to EVs and HEVs

Abstract

Sensorless control is a promising alternative for controlling Electric Vehicle (EV) and Hybrid Electric Vehicle (HEV) propulsion systems without the need of complex devices, such as resolvers or encoders. As the usage of a physical sensor is avoided, this allows significant cost reductions of the drive, and the reliability of the system is also improved. EVs require an operation range from standstill to high speeds. At low speeds, the back-EMF of the electric machine is low, and signal injection techniques are required in order to estimate the position and speed of the machine. This paper presents practical implementation details of the High Frequency Injection (HFI) technique, giving special attention to signal processing, offset compensation due to filtering delays and robust speed estimation. The approach is validated in an automotive Permanent Magnet Assisted Synchronous Reluctance Machine (PM-assisted SynRM) of 51 kW.