Injection Sequence Design for Mitigating High-Frequency Current in Low-Speed Sensorless Control Using Single DC-Link Current Sensor

Position sensorless control using single current sensor is widely used in cost-effective applications, as it minimizes the number of sensors in ac drive systems. The low-speed sensorless control method, which uses current derivative measurements, improves position estimation accuracy; however, it requires additional voltage injection, resulting in increased high-frequency (HF) current and acoustic noise. Therefore, this paper proposes injection sequence designs to mitigate additional HF currents. Based on the definition of three injection units, two injection sequences are proposed by the combination of these injection units. By decoupling the position estimation period and the current reconstruction period from the switching period, the proposed injection sequence design effectively reduces HF currents. The proposed injection sequence design method was validated on a 1 kW IPMSM experimental platform, demonstrating a reduction in total harmonic distortion of phase current by more than 4% and a decrease in sound pressure level compared to the conventional injection method.