INVESTIGATION ON MRAC BASED DIRECT TORQUE CONTROL OF IPMSM DRIVE

Abstract

Electric drives are considered the workhorse of many industrial and domestic applications. With the advancement in technology and depletion of fossils at a faster rate, applications like ground, aerial and marine vehicles are heading towards electrification. Consequently, it expands the region of application for electric drives. Electric drive is a term given to an electrical machine when controlled by semiconductor devices. Thus, electric drive is a combination of main areas of electrical engineering i.e. Electrical Machines and Power Electronics. Initially, the DC drives were used in most of the applications. Most of them incorporated thyristor based power electronic converters. However, DC motors suffers the inherent disadvantage of the requirement of frequent maintenance due to carbon brushes and slip rings, higher cost, lack of over load capacity, etc. Therefore, the aforementioned demerits motivated many researchers to focus on finding alternatives. Thus, with the introduction of AC machines and modern semiconductor devices like MOSFET and IGBTs, DC drives became obsolete. In the present times, AC drives are most commonly used in a wide area of application. An AC motor drive has several advantages like low cost, ease of maintenance, higher efficiency, reliable and ruggedness. The most commonly used AC machine in an AC drive is the induction motor due to several advantages mentioned before. However, the induction motor suffers the drawbacks of always operating at a lagging power factor. Consequently, many researchers are attracted to other replacement motors. Special motors like switch reluctance motor (SRM), permanent magnet synchronous motor (PMSM) are most likely to be used in the drive application in the present times. PMSMs are gaining popularity due to several advantages such as higher efficiency, effective cooling of the machine through the stator, reduction of the machine frame size and higher power/weight ratio. The other advantages are high air gap flux density, large torque/inertia ratio, small torque ripples, high speed operation, high torque capability (quick acceleration and deceleration) and compact design. However, the permanent magnets used in the rotor structure are received from rare earth materials and have a very high cost. However, with the development in the field of materials, many new materials with very strong magnetic properties are found. Consequently, the disadvantage of the higher initial cost will no longer be of worry in future times.