ABSTRACT:
Direct
torque control (DTC) is a suitable control method for electric drives which are
supplied by inverters, specially voltage source inverters (VSI). This method
has some advantages compared with other methods such as field oriented control
(FOC) with some drawbacks like switching frequency variation, that leads to
introduce DTC improvement methods. Using space vector modulator (SVM) in DTC
structure is the most important method that is referred to as space vector
modulator for direct torque control (SVM-DTC). Utilizing regenerative braking
method in electrical transportation makes it necessary to analyze the traction
motor behavior in regenerative braking mode. In this paper three major types of
SVM-DTC are mentioned and SVM-DTC method with Closed Loop Torque and Flux
Control in the Stator flux coordinates is used for simulation of traction motor
driver of Ghatar Shahri Esfahan Organization. Moreover, traction motor behavior
in regenerative braking mode using SVM-DTC driver is simulated.The simulation
results are analyzed in the paper
KEYWORDS:
1.Direct
Torque Control (DTC)
2. Space
Vector Modulation (SVM)
3. Traction
Motor Drive
4. Speed
Control of Induction Motors
5.
Regenerative Braking.
SOFTWARE: MATLAB/SIMULINK
BLOCK DIAGRAM:
Fig. 1. Block
diagram of DTC
Fig. 2. Block diagram of SVM-DTC
based on closed loop flux and torque control in stator flux coordinates
SIMULATION RESULTS:
Fig. 3. Applied load torque at
speed 0[201.4 rad/s.
Fig. 4. Simulation results of
SVM-DTC with reference speed of 201.4 rad/
Fig. 5. Applied load torque at
speed of 170 rad/s
Fig. 6.simulation results of
SVM-DTC with reference speed of 170 rad/s.
Fig. 7 DC-link behavior during
regenerative braking with and without regenerated energy absorption.
Fig. 8. Traction motor and
DC-link behavior during regenerative braking with regenerated energy absorption.
CONCLUSION:
In
the case of induction traction motor control methods ,DTC has better
performance. DTC has some shortcoming such as varying switching frequency
proportional to motor speed variation. Therefore, it is necessary to use
maximum sampling frequency in DTC. These issues result in increasing flux
ripple in lower speed and increasing torque ripple in higher speed in addition
to increasing switching loss. SVM-DTC with fixed switching frequency solves
these problems significantly. Among different methods of electrical braking,
regenerative braking has special advantages such as reduction in energy
consumption and improvement in power quality of DC link. SVM-DTC operation is
also appropriate and acceptable in regenerative braking. Therefore, it is
suggested to utilize SVM-DTC in electric rail transportation applications
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