Inductance Evaluation and Sensorless Control of a Concentrated Winding PM Vernier Machine

Due to the advantages of high torque density and simple mechanical structure, permanent magnet vernier (PMV) machines have attracted more and more research interests. In this paper, the inductance nonlinearity of an advanced concentrated winding PMV machine is investigated with consideration of both magnetic saturation and cross-coupling saturation under different d-axis and q-axis current loading. Then, the mathematical model with a variable inductance matrix of the PMV machine is established through incorporation of the finite-element analysis and the surface fitting method. Further, a back electromotive force based sensorless control method is developed for this PMV machine model with design of a current-dependent state observer. Based on the sensorless algorithm, the influence of inductance variation on rotor position estimation performance is then quantitatively evaluated. Simulation results show that the PMV machine can be well controlled for steady- and dynamic-state operation, and the position estimation error is effectively decreased. Finally, the proposed sensorless control algorithm is validated through experimental tests of the PMV prototype machine.