Research On Inner-feeding Cascade Speed Drive System By PWM Inverter

As fans and pumps are widely used in industrial field, and huge power is consumed, in response to national calls for energy conservation and emissions reduction, it is very significant to promote the technology of the speed adjustment on the load of high power fans and pumps.In recent years, with the fast development of electronics technology and computer control technology, the traditional cascade speed technology is paid more attentions again. However, as the waveform distortion by the grid-side、harmonic pollution and lower power factor at low speed can be caused by the thyristor commutation, the inner-feeding cascade speed drive system with chopper based on PWM inverter is put forward in this paper. The system not only retains the advantages of the traditional cascade control system, but also improves the power factor of the system. So it has a good prospect of energy saving in the high-voltage and large-capacity motor speed.The structure and the principle of the inner-feeding cascade speed drive system with chopper are firstly introduced in this paper. By the analysis of harmonics and power factor of traditional cascade control system, the feasible solution is proposed to improve the power factor of the system by adding on PWM inverter technology. The main circuit and principle of PWM inverter are in depth analyzed and based on it the system diagram of the inner-feeding cascade speed drive system with chopper in dq coordinate system is built. At the same time, the speed loop and current loop are modeled and the mathematical model of inner-feeding motor is established by software MATLAB/SIMULINK. By the simulation of PWM inverter and the inner-feeding cascade speed drive system with chopper, it proves the feasibility of this system.Finally, the main aspects of hardware circuit and software flow chart are designed and by related experiments, it proves that the solution of the system is feasible and it has a great potential for development.