Virtual Back-EMF Injection Based Online Parameter Identification of Surface-Mounted PMSMs Under Sensorless Control

Rotor position error under sensorless control will lead to parameter identification errors of surface-mounted permanent magnet (PM) synchronous machines (SPMSMs). In this article, a novel signal injection method is proposed for the first time, i.e., two additional virtual back-electromotive forces (EMFs) with equal amplitudes as perturbation signals are injected into a position observer. By injecting a positive and a negative virtual back-EMF, it is found that position error caused by parameter errors and inverter nonlinearity maintains constant and is only related to the ratio of
q
- and
d
-axis voltage fluctuations. As a result, the correlations of phase inductance, resistance, and PM flux linkage with the measured
dq
-axis currents/voltages can be established, in which the influence of both position error and inverter nonlinearity can be completely cancelled. Subsequently, by developing a full-rank model under two
d
-axis current conditions, the phase resistance, inductance, and PM flux linkage can be accurately identified. The experiment results show good performance of the proposed identification method under sensorless control.