Improved DTC of six-phase Induction machine in Phase fault in high power and high reliability aplication

In this research, a proper Duty Cycle Control method in Direct Torque Control (DTC) of six-phase induction machine in open phase mode is proposed. In conventional switching table DTC of six-phase induction machine, the torque and flux ripples are high and large harmonics by order (6𝑘±1) are produced. To overcome to this disadvantages a control method based on duty cycle control is used which produce less torque and flux ripples and harmonics losses. In this research, instead of using the common way to obtain new switching table in open phase mode, a new switching table is presented that can be combined to duty cycle method to achieve better results in open phase mode. In this method a simple and useful control method to calculate the duty cycle of each vector which is independent from machine parameters is used. Without considering the open phase fault, this technique has these advantages: less torque and flux ripples, independent from the load and speed changes, less current harmonics and almost sinusoidal shape, and zero power loss in (𝑧1−𝑧2) subspace. In addition, in open phase mode the results are acceptable and the machine continues to operate without speed drops. The simulation results presented in this paper show the preference of the proposed methods.