Determination of the inductance parameters for the decoupled d-q model of double-star permanent-magnet synchronous machines

Analytical models are the key tools in the model-based control design of electric drives. The inductances together with the stator resistance are the fundamental parameters of these models. In this study three methods to determine the inductances of the decoupled d-q model of double-star permanent-magnet (PM) synchronous machines are studied. These methods have commonly been used to determine the inductances of conventional three-phase PM machines. Two of the evaluated methods are based on the phase-variable inductance waveforms and flux linkages and are thus analysed with finite-element analyses only. The third method, based on the analytical stator voltage equations, can be applied straightforwardly with the real drive system supplied with voltage-source inverters (VSIs). This method requires only the knowledge of the rotor position and the existing current measurements of the VSIs that are used for the current control. Experimental results are provided to verify the applicability of the voltage-equation-based method to determine the inductances. On the average, the presented methods provide similar values, but also some discrepancies between the obtained values can be observed. The measured inductance parameters are validated using model-based closed-loop controllers.