Implementation of Induction Motor Drive Control Schemes in MATLAB/Simulink/dSPACE Environment for Educational Purpose

Squirrel-cage induction motors (IM) are the workhorse of industries for variable speed applications in a wide power range that covers from fractional watt to megawatts. However, the torque and speed control of these motors is difficult because of their nonlinear and complex structure. In the past five decades, a lot of advanced control schemes for IM drive appeared. First, in the 1960’s, the principle of speed control was based on an IM model considered just for steady state. Therefore, the so-called “scalar control methods” cannot achieve best performance during transients, which is their major drawback. Afterwards, in the 1970’s, different control schemes were developed based on a dynamic model of the IM. Among these control strategies, the vector control which is included in the so-called field oriented control (FOC) methods can be mentioned. The principle of vector control is to control independently the two Park components of the motor current, responsible for producing the torque and flux respectively. In that way, the IM drive operates like a separately excited dc motor drive (where the torque and the flux are controlled by two independent orthogonal variables: the armature and field currents, respectively). Since the 1980’s, many researchers have worked on improvements of the FOC and vector control which have become the industry’s standard for IM drives. Moreover, these researches led to new control strategies such as direct self control (DSC) or direct torque control (DTC). The principle of DTC is to control directly the stator flux and torque of the IM by applying the appropriate stator voltage space vector. With vector control, FOC, DSC and DTC, the major drawback of the scalar control is overcome because these control schemes are based on a model of the IM which is considered valid for transient conditions (Santisteban & Stephan, 2001). Both DTC and DSC possess high torque dynamics compared to vector control and FOC (Böcker & Mathapati, 2007). However, these two first control techniques have the drawbacks of variable switching frequency and higher torque ripple. The use of space vector pulse-width-modulation (SV-PWM) in conjunction with DTC (called, in this chapter, DTC-space vector modulation or DTC-SVM) has been proposed as a solution to overcome these drawbacks (Rodriguez et al., 2004), but sticking to the fundamental concept of DTC. The objective of this chapter is neither to do an overview of all IM control methods, as is done, e.g., in (Böcker & Mathapati, 2007; Santisteban & Stephan, 2001), nor to try to