Direct torque control (DTC) is a new method of induction motor control. The key issue of the DTC is the strategy of selecting proper stator voltage vectors to force stator flux and developed torque within a prescribed band. Due to the nature of hysteresis control adopted in DTC, there is no difference in control action between a larger torque error and a small one. It is better to divide the torque error into different intervals and give different control voltages for each of them. To deal with this issue a fuzzy controller has been introduced. But, because the number of rules is too high some problems arise and the speed of fuzzy reasoning will be affected. In this paper, a comparison between a new fuzzy direct-torque control (DTFC) with space vector modulation (SVM) is made. The principle and a tuning procedure of the fuzzy direct torque control scheme are discussed. The simulation results, which illustrate the performance of the proposed control scheme in comparison with the fuzzy hysteresis connected of DTC scheme are given.
1. Induction machine
2. Direct torque control
3. Fuzzy logic
4. Space vector modulation
Fig. 1. A novel direct torque control scheme for ac motor drives (DTC) with fuzzy hysteresis and space vector modulation
EXPECTED SIMULATED RESULTS:
Fig.2. response of trajectory of flux, electromagnetic torque and stator current for scheme of simulation results of fuzzy-hysteresis regulators connected
Fig. 3. response of trajectory of flux, electromagnetic torque and stator current for scheme of DTC- fuzzy hysteresis with SVM
In this paper, a fuzzy direct torque control with space vector modulation is analyzed in comparison to fuzzy hysteresis connected of DTC. The results obtained by numerical simulation are given. In short, the advantages of proposed fuzzy direct torque control using space vector modulation technique in comparison with a fuzzy hysteresis of DTC are the following:
– Reduced torque and flux distortion;
– Constant switching frequency thanks to apply SVM;
– Fast torque response because of the use of fuzzy controller;
– Lower sampling time;
– No problems during Low-speed operation;
– No current and torque distortion caused by sector changes.
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