1 Simulation of DTC Strategy in VHDL Code for Induction Motor Control IEEE ISIE 2006, July 9-12, 2006, Montreal, Quebec, Canada 指導教授： 龔應時 學 生： 顏志男 Marcelo F. Castoldi, Manoel L. Aguiar ptt 製作 :100%

2 OUTLINE ABSTRACT INTRODUCTION DTC STRATEGY VHDL AND FLOATING POINT SIMULATION RESULTS CONCLUSIONS

3 ABSTRACT This paper presents a simulation of Direct Torque Control (DTC) strategy, used to control induction motors. This simulation was realized with Matlab and Modelsim programs. The Matlab/Simulink was used to simulate the motor dynamics and the inverter of the control system. The DTC strategy was executed in Modelsim using VHDL floating point.

4 INTRODUCTION The present paper shows the simulation ofthe DTC induction motor drive using Matlab and the Modelsim programs operating simultaneously. The power-drive and the induction motor model have been implemented in the Matlab/Simulink program. The calculations of DTC strategy was implemented in VHDL code using Modelsim program. The Link-for-ModelSim toolbox executes the cosimulation using a VHDL code font running in ModelSim program.

5 DTC STRATEGY(1/3) The DTC technique is a control principle of optimized AC drive, where the inverter's switching controls directly the flux and torque motor variables [7]. The inverter's switches impose the required voltages on the motor, which will control both torque and flux in a closed-loop control. The DTC technique is represented by Fig. 1.

6 DTC STRATEGY(2/3)

7 DTC STRATEGY(3/3) The motor model calculates the stator flux and torque magnitudes and the flux spatial sector in the stationary stator reference frame.

8 VHDL AND FLOATING POINT VHDL is a code for VHSIC (Very High Speed Integrated Circuit) hardware description standardized for IEEE , which offers many advantages for digital projects [9]. Although integer numbers supply accurate representation of numerical values, they have a great disadvantage: the inability to represent fractionary values. Arithmetic in floating-point resolves this problem. It causes a loss of speed, however, the benefits with its use surpasses this disadvantage. The ANSI/IEEE 754 standard was created to facilitate the portability of programs, which use floating-point, between different computers.

9 SIMULATION(1/2) In this project, the DTC strategy was simulated, using general Simulink blocks, Power System-Blockset modules and a block for co-simulation in VHDL. The system used can be seen in Fig. 3. The flux motor model, as well the hysteresis comparators of flux and torque and the flux spatial sector are the first part ofthe VHDL code. This methodology was applied to simulate the routine that can be later implemented in FPGA's.

10 SIMULATION(2/2)

11 RESULTS(1/7) The results were analyzed comparing the VHDL simulation results to the Matlab results. The latter results were obtained through the Machines Measurement Demux toolbox (SimPowerSystems). The system simulation of Fig. 3 was started setting a value for torque and flux references. The motor data are:

12 RESULTS(2/7)

13 RESULTS(3/7)

14 RESULTS(4/7)

15 RESULTS(5/7)

16 RESULTS(6/7)

17 RESULTS(7/7)

18 CONCLUSIONS The simulation proposal using Matlab and Modelsim programs in cosimulation mode has presented satisfactory results as demonstrated in this work. The VIHDL code using floating-point presented good results and very accurate calculations of the motor parameters, providing the good functioning of the DTC. Another significant advantage of the co-simulation aspect is the great risk reduction of significant changes in the code for one future implementation in the hardware.