Implementation Of Direct Torque Control Of Induction Machines Utilizing ezDSP F28335 And FPGA

Muhd Khairi, Abd Rahim (2013) Implementation Of Direct Torque Control Of Induction Machines Utilizing ezDSP F28335 And FPGA. Project Report. UTeM, Melaka, Malaysia. (Submitted)

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Abstract

This thesis presents the implementation of Direct Torque Control (DTC) of induction machine utilizing ezdsp F28335 and FPGA. It is well-known that the DTC method has widely been acceptance for advanced motor control in many industrial applications due to its simplicity and high-torque control performance. However, the DTC has some major problems which are larger torque ripples, variable switching frequency due to the hysteresis controllers and initial and drift problem in estimating the flux because of the use of pure integrator. The research project aims to minimize the problems so that the high DTC performance can be achieved. To minimize the torque ripple, it is necessary to reduce the computational burden in executing the DTC algorithm by applying two digital controllers, i.e. ezdsp F28335 and FPGA. By distributing some tasks of DTC algorithm to be executed on the FPGA, the ezdsp manages to perform the sampling frequency at 20 kHz. Moreover, the DTC algorithm executed in ezdsp was based on the optimal IQ-Math calculation approach that guarantees lesser calculation times required with minimized calculation error. By doing like this, the bandwidth of hysteresis as well as torque ripple can be reduced as the hysteresis operation similar to the analogue one. On the other hands, the second problem can be solved by applying a low pass filter in the integration of flux estimator. The IQ-math blocks were used to construct the improved estimator with a cut-off frequency is set at 5 rad/s. The improvements of DTC performance were verified through simulation and experimental results.

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