Low-Speed Sensorless Control of Switched Reluctance Motor Drives Using Random Pulse Injection for Noise Reduction

To reduce copper loss and noise caused by high-frequency pulse injection (HFPI), this article proposes a random pulse injection method based on a proportional-integral control duty cycle (PI-RPI) for sensorless control of switched reluctance motors (SRMs) at low speed. Conventional injection methods use a fixed-voltage duty cycle for position estimation, while the induced current in the idle phase varies with the rotor position, which will produce a large copper loss. In addition, fixed-frequency signal injection causes discrete harmonics in the current power spectral density (PSD), which results in extra noise. The above problems reduce the efficiency of the drive system and limit the use of traditional sensorless methods. This article first introduces the traditional HFPI method. Based on that, the copper loss of the idle phase is reduced by closed-loop control of the induced current using a proportional-integral (PI) controller. Then, a novel random pulse injection method using H-bridge topology is proposed, which eliminates discrete harmonics in the current PSD by injecting pulses of random frequency and direction. The current PSD of the proposed PI-RPI method is compared with the conventional methods. The effectiveness of the proposed sensorless control scheme is verified on a 750-W SRM setup.