HF Test Current-Ripple-Control-Based Sensorless Method for SynRMs in the Low- and Zero-Speed Range Leading to an Adaptive Square-Wave-Shaped Voltage Injection

Extending the bandwidth of high-frequency test signal-based sensorless control methods for low- and zero-speed ranges can be achieved by increasing the test signal frequency. A square-wave-shaped voltage injection (SWSVI) enables this. Originally, a SWSVI is a pure alternating voltage injection with a constant voltage amplitude. However, it is recommended to use adaptive voltage levels for Synchronous Reluctance Machines (SynRMs), otherwise the non-linear machine behaviour will result in operating-point-dependent current responses and therefore cause additional audible noise and HF losses. This method has the disadvantage that the operating-point-dependent voltage levels have to be determined in advance. This paper proposes an alternative to pure adaptive SWSVI that actively controls the high-frequency (HF) current ripple caused by SWSVI using a HF current control with a static pre-control. Experimental results demonstrate the good performance of this sensorless control method.