Research Of Parallel-connected Multi-induction Motor Drive System

With the rapid development of the railway traction system, the traction drive system of railway traction system tends to be light weight,small size, low cost and high reliability. In railway traction system, two to four induction motors operating in parallel are required to ensure the normal running. Thus the control strategies of single inverter single motor can't meet the requirement. And it is necessary to study the control strategies and the system of multi-induction motor drive system.According to the dynamic model of induction motor and vector control theory on single induction motor, the vector control systems of two paralle1-connected induction motors is established which takes the different parameters and unbalanced loads of motor into account while combining the idea of the average.At the same the simulations are finished on the condition of the torque step change and the speed step change. The simulation results show that the system has good performance in dynamic state and stable state.According to the vector control theory of four paralled-connected induction motors, the derivation processes of the flux model and torque model of the four parallel-connected induction motor drive system are given. And the vector control systems of four parallel-connected induction motor are designed.Because of the limitations of PI control when applying to the ac speed regulating system,the paper makes full use of the advantages of fuzzy logical PID.Regardless of unbalanced loads at starting, unbalanced loads at running or balanced loads at running, The simulation results show that the system can run more smoothly and has a better dynamic and static performance when adopted the fuzzy logical PID.The study of scheme is of significance, especially in rail transport.