Abstract:

The traditional model predictive torque control has the advantages of simple principle, fast dynamic response and flexible control. It has been widely studied in the high-performance control of induction motor. However, the existing methods usually obtain the torque reference command through the outer speed loop, while the torque and flux tracking are realized through the model predictive control of the inner loop. Although the cascaded double-loop structure ensures the stability of the system, it has some disadvantages, such as the interaction between the inner and outer loops, more debugging parameters and so on. To solve the above problems, the cascaded double-loop structure in the traditional control scheme is eliminated, and a model predictive direct speed control method including only a single control loop is proposed. By introducing stator flux linkage error and rotor speed error into the cost function, the simultaneous control of speed and flux linkage with different time scales is realized, which has the advantages of simple structure and few debugging parameters. In addition, the steady-state performance of speed control is improved by introducing load torque observation. Compared with the traditional model predictive torque control, the proposed model predictive direct speed control significantly reduces the torque and speed ripple. In addition, it has lower current harmonics in the full speed range. The effectiveness of the proposed method is verified by experiment results.

Key words: Induction motor, direct speed control, single control loop, steady-state performance