A High Frequency Injection Technique With Modified Current Reconstruction for Low-Speed Sensorless Control of IPMSMs With a Single DC-Link Current Sensor

This paper proposes a high frequency injection technique applied for low-speed sensorless control of interior permanent magnet synchronous machines (IPMSM) with a single dc-link current sensor. The three-phase currents, which can be reconstructed by the measurement of a dc-link current sensor, always suffer from the immeasurable regions. The most challenging problem exists in the low modulation region, where no phase current can be measured by the dc-link current sensor, and it is rarely solved without PWM modifications. This paper proposes a six-direction square wave high frequency injection method to extend the voltage vector to the measurable region to achieve the three-phase current reconstruction and saliency-based sensorless control without modifying the space vectors of the pulse width modulation (PWM). In addition, the paper comes up with a modified reconstruction scheme to reduce the reconstruction error and improve the accuracy of the position estimation. This low-speed sensorless strategy using a single dc-link current sensor is implemented in dSpace platform and the performance is evaluated by experiments.