Vector Control of 3-Phase Induction Motor

Widely used in many industrial applications, the induction motors represent the starting point when an electrical drive system has to be designed. In modern control theory, the induction motor is described by different mathematical models, according to the employed control method. In the symmetrical three-phase version or in the unsymmetrical two-phase version, this electrical motor type can be associated with vector control strategy. Through this control method, the induction motor operation can be analyzed in a similar way to a DC motor. The goal of this research is to summarize the existing models and to develop new models, in order to obtain a unified approach on modelling of the induction machines for vector control purposes. Starting from vector control principles, the work suggests the d-q axes unified approach for all types of the induction motors. However, the space vector analysis is presented as a strong tool in modelling of the symmetrical induction machines. When an electrical motor is viewed as a mathematical system, with inputs and outputs, it can be analyzed and described in multiple ways, considering different reference frames and state-space variables. All the mathematical possible models are illustrated in this report. The suggestions for what model is suitable for what application, are defined as well. As the practical implementation of the vector control strategies require digital signal processors (DSP), from the continuous time domain models are derived the discrete time domain models. The discrete models permit the implementation of the mathematical model of the induction motors, in order to obtain high efficiency sensor-less drives. The stability of these various models is analyzed.