| Abstract |
Sensorless control of induction motor (IM) drives has received wide attention in last few years. The main reason is that the use of speed sensor spoils the ruggedness and simplicity of IM. Even more, in a hostile environment speed sensors cannot be mounted. However, due to the high order and nonlinearity of the dynamics of an IM, estimation of the angle speed and rotor flux without the measurement of mechanical variables becomes a challenging problem. To overcome this, various speed sensorless control algorithms have been presented. Due to its order reduction, disturbance rejection, strong robustness, and simple implementation by the means of power converter and digital signal processors, sliding mode control (SMC) theory is one of the prospective control methodologies for electric machines. In this paper, an SMC based rotor flux observer is designed and a sliding mode approach is applied to the torque tracking control of the IM. In principle, the proposed method is based on driving the stator flux towards the reference stator flux vector defined by the input commands, the reference torque and the reference rotor flux. This action is carried out by the robust sliding mode flux controller applying a suitable stator voltage vector to the machine in order to compensate the stator flux vector error. Sensorless torque and flux control of an IM is an emerging new technology, though in the early state of development. A sliding mode algorithm for torque and flux tracking control is presented in the paper. The algorithm is aimed to solve practical highly nonlinear problem of the operation of IM at high and low speed including zero speed. This algorithm is especially suitable for the applications where desired torque and rotor flux are varying during the operation. For example when efficiency of the IM operation is an important issue, like in electric vehicles. The performance of the proposed algorithm was verified by the simulations and experiments. |
