Sensorless control of single and dual three phase interior permanent magnet synchronous machines with inductance asymmetries

This thesis presents a comprehensive study on the effect of inductance asymmetries, including self-inductance asymmetries and single open phase faults, and their compensation methods, in high-frequency (HF) signal injection (HFSI) sensorless control of single three-phase (STP) and dual three-phase (DTP) interior permanent magnet synchronous machines (IPMSMs).
Inductance asymmetries, caused by manufacturing tolerances and winding faults etc., can introduce harmonic distortions in the estimated rotor position, deteriorating the performance of HFSI sensorless control systems. It is found in this thesis that the self-inductance asymmetries in multiple phases can cause the 2nd- and 4th-order estimated position errors in HFSI sensorless controlled STP- and DTP-IPMSMs. When self-inductance asymmetries in multiple phases exist in both sets of three-phase windings of DTP-IPMSMs, apart from the 2nd- and 4th-order estimated position errors, there will also be a DC offset estimated position error. Besides, the single open phase fault can lead to a 2nd-order estimated position error in the HFSI sensorless controlled DTP-IPMSM system.
Compensation methods are proposed in this thesis to suppress the estimated position error caused by the inductance asymmetries. For the STP-IPMSM with self-inductance asymmetries in multiple phases, this thesis proposes a synchronous reference frame filter-based compensation method and an anti-rotating d-axis signal injection-based method to mitigate the 2nd-order harmonic estimated position errors. Then, for the DTP-IPMSM with one-set self-inductance asymmetries in multiple phases, this thesis proposes a current summation with a ratio-based method to compensate the 2nd-order harmonic estimated position error and an adaptive notch filter (ANF) -based method to compensate both the 2nd- and 4th-order harmonic estimated position errors. For the DTP-IPMSM with two-set self-inductance asymmetries in multiple phases, an Adaline filter-based compensation method is introduced to suppress both the 2nd- and 4th-order harmonic estimated position errors, and a current direct summation-based method is proposed to cancel the DC offset estimated position error. Finally, this thesis explores the effect of the single open phase fault on HFSI sensorless controlled DTP-IPMSMs, where the 2nd-order harmonic estimated position error can destabilise the HFSI sensorless control system. To address this, an ANF-based compensation method and a current summation with a ratio-based compensation method are proposed, offering a fault-tolerant HFSI sensorless control.