Variable-frequency asynchronous electric drive with pulse-width modulation and identification of its operation modes

Abstract

To implement automatic control of three-phase variable-frequency asynchronous electric drives, information is required on the values of some internal parameters of an asynchronous motor used in agriculture. These values are used when setting up automatic electric drive controllers and when indirectly determining the energy mode of operation of an asynchronous electric motor. In connection with the improvement of modern structural diagrams of automatic control of an asynchronous electric drive, there is an increasing need to develop algorithms for identifying the internal parameters of an asynchronous electric motor where phase voltages and currents are measured at the terminals of the frequency converter thereby eliminating the installation of special sensors for monitoring and calculating flux linkage. Sensorless systems are increasingly widely used methods for calculating the generalized flux linkage vector and its projections form the basis of the universal identification algorithms developed in this study. This paper concerns mathematical analysis of the initial theoretical principles for identifying the internal parameters of a frequency-controlled squirrel-cage AC induction electric drive and proposes multifunctional algorithms for reading a number of internal parameters of an AC electric motor mode which is especially important when setting up automatic regulators and operating an asynchronous variable-frequency electric drive. By analyzing data from calculations of electromechanical and electromagnetic processes performed using developed identification algorithms with given values of internal parameters in the original mathematical model of an asynchronous motor, a discrepancy of 1-2% is found which indicates the achievement of a high degree of self-adjustment of the automatic regulator during commissioning and during variable-frequency drive operation.