Sensorless Control of Induction Motors with SiC Inverter Using High-Frequency Rotating Injection

Rotor position estimation accuracy is one of the major challenges of sensorless induction motor (IM) drives based on the conventional high-frequency rotating injection. This paper presents a sensorless control scheme with the high switching frequency characteristic of silicon carbide (SiC) devices to improve the rotor position estimation accuracy. Firstly, the impact of the high switching frequency and high injection frequency of SiC -based motor drives on rotor position estimation accuracy is analyzed, considering the high-frequency motor model, control delay, and filter characteristics. Further, the finite impulse response high-order bandpass filter (BPF) is adopted to replace the infinite impulse response 4th-order BPF at the high sampling frequency due to the filter group delay characteristic, which reduces the distortion of the carrier-signal negative-sequence current. The speed error is reduced by 4 rpm. This demonstrates that high injection frequency and filter optimization can improve the speed estimation accuracy. Finally, the sensorless scheme with SiC devices improves the low-speed control performance at 30 rpm, and verification experiments are conducted on a 7.5 kW IM drive platform.