Minimization of torque ripple for DTC CSI FED induction motor drives during low speed operation

Abstract

Three-phase squirrel-cage Induction Motors (IM) are used in many industries as drives in high-performance applications for their advantages such as rugged construction, less cost, easy maintenance, and reliability. Using advancement of power electronics and microelectronics the squirrel cage IMs can be easily controlled and operated for constant and variable speed applications. Voltage Source Inverter (VSI) with Pulse-Width Modulation (PWM) technique is used in variable-speed motor applications for low to moderate power. But, the switched voltages produce high voltage slopes over stator windings, which stress insulations and cause current newlinebearing probl ems. A possible solution is to use of Current Source Inverter (CSI) with PWM. Both voltages and currents of the machine are almost sinusoidal and, therefore, voltage stresses in the machine windings are lower. In PWM-CSIs a capacitor filter is inserted on the load side to reduce the current harmonics. A CSI can also be used for high-power applications; however, it has some drawbacks such as slower dynamic response and large size because of large smoothing inductor requirement at its dc source end. The On-line control strategy of CSI drive system is more complex compared to a VSI drive because of the CSI gating requirement. But depending on specific applications, its advantages can at times outweigh its disadvantages In recent years Current source inverter (CSI) is a suitable choice for variable speed applications in industries with high performance and high power newlinehandling capabilities. There are so many control methods available in which vector control techniques such as Field Oriented Control (FOC) and direct torque control (DTC) are quite dominant and easily adaptable for industrial drives. Field Oriented Control (FOC) and Direct Torque Control (DTC) techniques have their own highlights and advantages when applied in different Industrial applications.