Sensorless algorithm for synchronous machines using current oversampling and PWM harmonics

Sammanfattning: Sensorless-controlled drives represent a solution drawing an increasinglyimportant attention for the benefits they entail. At the cost ofa slightly lower dynamics compared with the traditional drives, theyinvolve a reduction of the system costs and complexity and improvednoise immunity and reliability. Besides the traditional signal injectionmethods, involving a limitation of the machine voltage margin, higheriron losses, torque ripple and acoustic noise, a new method has beenproposed in 2010 by professors Bolognani, Faggion and Sgarbossa.This algorithm, which has been defined "intrinsic injection" method,makes used of the harmonic content deriving from the PWM modulation.In this work, the intrinsic injection sensorless algorithm and its implementationin a MATLAB=Simulink environment is the object of study.Its theoretical foundation is deeply analysed together with the phenomenaand the operating conditions that might affect its performance.The drive model is described and three different alternatives for the estimatorhave been proposed. Simulations have been run with the estimatoroperating both in open-loop and in closed-loop. The influencesof the sampling frequency, of the motor speed, of the load torque, ofthe implemented modulation strategy and of the DC-link voltage amplitudehave been analysed. Lastly, the drive has been simulated withregard to a fan or pump application case.