Simulation and Comparison of 2-L & 3-L Inverter Fed Induction Motor DTC Drives

Abstract

Abstract-Direct I. INTRODUCTIONInduction motors are the most widely used alternative in adjustable speed drives. Field Oriented Control (FOC) [1], and Direct Torque Control (DTC) [2,3] have emerged as the standard industrial solutions for high dynamic performance operation of these machines.In particular DTC offers attractive performance in terms of fast torque response, simple and less computational cumbersome control schemes, robustness against parameter variation, no need of PWM modulator and current regulators. However it has some draw backs like torque ripple, variable switching frequency, electromagnetic compatibility due to high frequency harmonic current and voltage. In recent years, research is going on DTC for multi level converters [5,6,9] attractive solution for high power applications, due to higher voltage operation capability, reduced common mode voltages, near sinusoidal outputs, low dv/dt's and smaller or even no output filter [4]. The most attractive features of this technology are in the medium to high-voltage application range (2-13 kV), which include motor drives, power distribution, power quality and power conditioning applications [13]. One of the advantages of multilevel inverters is that the voltage stress on each switching device is reduced. In addition, multilevel waveforms feature have less harmonic content compared to two level waveforms operating at the same switching frequency .In multi level inverters, it is easy to reach high voltage levels in high power applications with lower harmonic distortion and switching frequency, which is very difficult to get this performance with conventional two level inverters. The high-voltage switches are rather expensive, the employment of the double number of the cheaper switches are often economical favorable. Simultaneously the less IM current and torque distortions can be achieved by using of the more number of the feasible inverter states [9].In this paper two different DTC schemes will be compared with each other. These two schemes are DTC-SVM with two-level inverter and DTC-SVM with threelevel inverter. The Proposed scheme is described clearly and simulation results are reported to demonstrate its effectiveness. The entire control scheme is implemented with Matlab/Simulink. II. DTC-SVM WITH TWO-LEVEL INVERTER A. Vector Model of Inverter Output VoltageIn the PWM voltage source inverters, considering the combinations of the states of switching functions inverter switching state functions (C1, C2, and C3) which can take either 1 or 0, the voltage vector becomes.Eight switching combinations can be taken according to the above relationship: two zero voltage vectors and six non-zero voltage vectors show by Fig.2 [1][2]. B. Stator Flux and Torque EstimationThe components of the current (Isα, Isβ), and stator voltage (Vsα, Vsβ) are obtained by the application of the transformation given by (5) and (6)

Direct torque control of multilevel SVPWM inverter in variable speed SCIG-based wind energy conversion system

“…In that way, applying same standards to the hexagon produced by inverter voltage vectors, the first sextant given or mal results on Fig. 19 [29].…”

Direct torque control based on second order sliding mode controller for three-level inverter-fed permanent magnet synchronous motor: comparative study

“…DTC with three-level inverter. The principle of the DTC is to maintain the stator flux within a specific range [3,4]. This technique is based on the direct determination of the commands sequences applied to the switches of a three level inverter.…”