Comparative Analysis of Hysteresis Current Control and SVPWM on FLC based Indirect Vector Controlled Induction Motor Drive

Abstract

Over the years,Induction motors (IM) are widely used in many industrial applications as workhorse, because of its advantages such as simple and robust in construction, highly reliable and capability of working in extreme conditions. However, as compared to DC motor speed control of IM is complex due to coupling between flux and torque components of currents. Speed of IM controlled either by scalar control technique or by vector control technique. Scalar control technique is preferred in many applications for speed control of IM due to its simplicity. In scalar control, speed control of IM obtained by regulating magnitudes of stator voltage and frequency. However, this technique suffers with poor dynamic response. To enhance dynamic response, vector control technique preferred for speed control of IM. With vector control technique, IM behaves like a separately controlled DC motor. However, this technique employs coordination transformations, modulation techniques and current controllers. Vector control technique classified into two categories based on unit vector generation named as direct vector control and indirect vector control. In direct vector control technique, unit vector estimated using hall sensors. However, placing these sensors on stator poles is difficult. Indirect vector control overcomes these drawbacks. Proportional-Integral (PI) controller used in indirect vector controlled IM drive to control speed. However, this PI controller requires accurate gain values for better performance. As operating conditions changes, tuning of PI controller gains required for high performance IMD. Moreover, PI controller is unable perform satisfactorily with load torque and speed changes. Therefore, fuzzy logic controller (FLC) used to replace PI speed controller. FLC is simple to implement without any mathematical equations.
Modulation techniques required to produce gating pulses for inverter switches. Modulation techniques broadly classified into two categories such as voltage and current control methods. Voltage control again subdivided as sinusoidal pulse width modulation (SVPWM), space vector pulse width modulation (SVPWM) techniques. Similarly, current control divided into hysteresis and delta control. Among all these techniques, SVPWM and Hysteresis control techniques are preferred in high power applications. Hysteresis control is
simple and can give fast response but it suffered with variable operating switching frequency. SVPWM technique can give good steady state response with fixed switching frequency.