Seamless integration of a low-speed position estimator for IPMSM in a current-controlled voltage-source inverter

This paper deals with the seamless integration of high-frequency test voltages for IPMSM rotor-position estimation in the discrete-time current-controller with fixed sampling frequency of a voltage-source converter. Pulsed test voltages are used that don't interfere with the current samples taken to control the phase currents. For this purpose, an asymmetric pulse-width modulator is applied. As a result of this strategy, the controller output influences the test voltages and consequently the current response from which the rotor position is estimated. Therefore, in this paper, a first strategy is studied in which the applied test voltages are computed taking into account the controller output. A second method is discussed as well in which the controller output is slightly delayed so that this output has no influence on the test signals. Despite the disadvantage of a small time delay, compared to the first method, no additional calculations are required to compute the test voltages.