Parameter sensitivity analysis of an improved open-loop speed estimate for induction motor drives

The paper presents a detailed sensitivity analysis comparison between two existing low-cost sensorless solutions for induction motor drives. The first solution is a V-type approach, in which the inverter voltage references are calculated from the machine equations instead of obtained as the output of PI current regulators. The scheme is obtained from a standard field oriented control drive by successive approximations. The second solution is an open- loop speed estimator, based on the machine equations only, used in conjunction with a field oriented control drive with speed and current closed loops. An analytical sensitivity analysis has been carried out first, looking for the behaviour of the two schemes in presence of single motor parameter mismatch. Both schemes have been implemented in laboratory prototypes, and their performances have been tested in different conditions. The results of the comparison are discussed in details. A side value is the generality of the proposed analysis method, which can be applied as a standard comparison tool for control schemes evaluation.