An I-f Startup Method with Compensation Loops for PMSM with Smooth Transition

The back-EMF based sensorless drive of permanent magnet synchronous machines (PMSMs) is attractive for many industrial applications due to its simplicity and good reliability. For applications such as pumps and fans, in which there is no demand for high dynamic performance in the low-speed range, the I-f method for startup is considered as a much simpler solution than many high-frequency signal injection methods. This paper proposes an I-f startup method that enhances the performance by adopting a frequency compensation loop to improve the system stability and a current vector magnitude compensation loop to obtain a smooth transition to back-EMF based sensorless field-oriented-control (FOC). The experimental results verify the effectiveness of the proposed method and its superior performance compared with the existing I-f starting method.