Direct Torque Control of Induction Motor Drive With Flux Optimization

ABSTRACT:

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

KEYWORDS:

                          1.Direct Torque Control,

                          2. Induction Motor,

                          3. Flux Optimization

SOFTWARE: MATLAB/SIMULINK

BLOCK DIAGRAM:

Figure 1: Block Diagram of Conventional DTC Scheme

 

Figure 2: Block Diagram of the Flux Optimized DTC Scheme

EXPECTED SIMULATION RESULTS:

                              

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

CONCLUSION:

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.

REFERENCES:

[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