Search This Blog

Monday, 8 February 2016

Direct Torque Control of Induction Motor Drive With Flux Optimization


MATLAB / SIMULINK implementation of the Direct Torque Control Scheme for induction motors is presented in this paper. Direct Torque Control (DTC) is an advanced control technique with fast and dynamic torque response. The scheme is intuitive and easy to understand as a modular approach is followed. A comparison between the computed and the reference values of the stator flux and electromagnetic torque is performed. The digital outputs of the comparators are fed to hysteresis type controllers. To limit the flux and torque within a predefined band, the hysteresis controllers generate the necessary control signals. The knowledge about the two hysteresis controller outputs along with the location of the stator flux space vector in a two dimensional complex plane determines the state of the Voltage Source Inverter (VSI). The output of the VSI is fed to the induction motor model. A flux optimization algorithm is added to the scheme to achieve maximum efficiency. The output torque and flux of the machine in the two schemes are presented and compared

                          1.Direct Torque Control,
                          2. Induction Motor,
                          3. Flux Optimization


Figure 1: Block Diagram of Conventional DTC Scheme


Figure 2: Block Diagram of the Flux Optimized DTC Scheme



Figure 3: Stator d-q flux space vector without flux optimization                     


 Figure 4: Stator d-q flux space vector with flux  optimization
Figure 5: Variation of Stator Flux – Conventional  DTC Scheme                                                                   

  Fig 6: Variation of Stator Flux - Optimized DTC scheme


Figure 7: Variation of Mechanical Speed – Conventional  optimized DTC scheme    

 Figure 8: Variation of Mechanical Speed - Optimized DTC scheme


Figure 9: Electromagnetic Torque - Conventional DTC

Figure 10: Electromagnetic Torque - Optimized  DTC
Figure 11: Percentage Efficiency of Flux Optimized DTC


In this paper, DTC for an induction motor drive has been shown along with flux optimization algorithm. DTC is a high performance, robust control structure. A comparative analysis of the two DTC schemes, with and without flux optimization algorithm has been presented. With flux optimization implementation, it is observed that the efficiency of the about 87 % has been obtained. MATLAB simulation of a 15 Hp IM drive has been presented to confirm the results.


[1] Werner Leonhard. Control of Electric Drives. Springer-Verlag Berlin Heidelberg, 1996.
[2] F. Blaschke. “The Principle of Field Orientation as Applied to The New Transvector Closed Loop Control System for Rotating Field Machines”. Siemens Review, pages 217–220, 1972.
[3] K. Hasse. “On The Dynamic Behavior of Induction Machines Driven by Variable Frequency and Voltage Sources”. ETZ Archive, pages 77–81., 1968.
[4] I. Takahashi and T Nogushi. “A New Quick Reponse and High Efficiency Control Strategy of an Induction Motor”. IEEE Trans. Industry Applications, IA -22:820–827, 1986.

[5] M. Depenbrock. “Direct Self Control (DSC) of inverter-fed induction machines”. IEEE Trans. Power Electronics, 3(4):420–429, 1988