Direct torque control of induction motor based on sliding mode

As a result of this study, an improved direct torque control (DTC) method based on sliding mode control (SMC) was used to control the sensorless three-phase asynchronous motor, as well as a third-order cascade inverter has a frequency-modulated carrier (FM—Frequency Modulation) to reduce total harmonic distortion (THD) in torque and current, in order to achieve the best possible result. The rapid change in current and voltage on the load caused oscillations around the sliding surface (chattering) that damaged the actuators by means of rapid changes and large amplitudes of current and voltage. This study, therefore, proposed the use of nonlinear Tansig functions rather than classical sign functions as the control algorithm. Additionally, due to the fact that direct torque control (DTC) had the advantage that it was not sensitive to motor parameters, thereby ensuring that, even when nonlinear parameters change with time, they did not affect the whole closed system as a whole. Hence, radial basis function networks (RBFNs) were used to approximate magnetic fluxes and torques. A simulation and experiment were conducted by OPAL-RT equipment on Matlab/Simulink for a squirrel-cage rotor motor 1 hp, 150 rad/s with third-order cascade inverter that has a frequency-modulated carrier. In spite of the change in torque in the presence of noise, the system remained stable regardless of the set value from the lowest velocity 3 rad/s to the highest velocity 150 rad/s. This algorithm was simple, required little memory, and had high-order harmonic components of torque and low current (THD-Total Harmonic Distortion). The algorithm had been proven to be stable by Lyaponov.