Comparison of incremental encoder digital signal processing techniques for theinduction motor flux-torque vector control systems

Abstract

The articlepresents the results of a study on the effectiveness of varioustechniques forsynchronous reference frame angular position numerical calculation in flux-torque vector control system of induction motor.Investigation was caried out taking into account the discrete nature of the angular speedsignal obtained using an incremental encoder. In this workfor investigation by simulation useda direct torque vector control system, which, in the presence of an ideal rotor angular speedsignal, ensures direct asymptotic field orientation, asymptotic tracking of torque-flux referencetrajectories, as well as asymptotic decouplingtorque and flux subsystems. The parameters of the inductionmotor and encoder used in the study correspond to those existing in traction electromechanical systems of city trolleybuses. It is shown that the discrete nature of the angular speedsignal, which usedin synchronous reference frameposition equation of flux-torque vector control systems, introduces field orientation errors and leads to current and torque ripples, which in a real system increase acoustic noise and can cause mechanical vibrations and resonance phenomena. An analysis of possible ways to reduce the influence of the speed signal discreteness on flux-torque control is performed, and a method for practical implementation of the synchronous reference frame angular position numerical calculationis proposed. This method allows ensuring conditions for more precisefield orientation and, by using an additional filter for the angular speedsignal, reducing the level of current and torque ripplesto negligibly small values without affecting the field orientation processes. The proposed solution can be used in the development of high dynamicflux-torque vector control systems for inductionmotors using incremental encoders, including for electric vehicles.