Design And Application Of Internal Feedback Chopper Cascade Speed Control System

In high voltage and large capacity motor system,because of high cost and large volume frequency conversion equipment,there are many problems in extensive application.For wind machines and pump load,cascade speed control is a very good program.The speed regulating device is changed from the stator side to the rotor side,it makes device structure simple,avoids high voltage,and reduces the capacity of the speed regulating device.However,the problems such as low power factor,serious harmonic pollution and so on,restrict its development.In this context,the internal feedback cascade speed regulation technology is studied on the basis of the traditional cascade speed regulation theory,it has the advantages of advanced technology,simple structure and easy maintenance,and can regulate speed continuous and smooth.It is suitable for large capacity square torque load such as wind machines and pumps.In this paper,the survey of AC speed regulation technology is introduced firstly,and then the principle and development of cascade speed regulation are analysed.Until now,Cascade speed regulation technology has gone through the traditional cascade speed regulation,internal feedback cascade speed regulation,internal feedback chopper cascade speed regulation and PWM converter cascade speed control and other stages.Based on the above analysis,internal feedback chopper cascade speed control system is analysed detailedly,and then the structure and working principle of internal feedback chopper cascade speed control system are analyzed.Aiming at problem of low power factor in the practical application,a cascade speed regulation system with PWM inverter is proposed.Based on the mathematical model of the internal feedback motor,the simulation model of the internal feedback motor and the speed regulation system is established,speed curve and current waveform of stator and rotor are get,so the feasibility of internal feedback motor and speed control system is verified.When the PWM inverter operates in capacitive resistance state,the system power factor remained unchanged.Then the parameters of the main circuit of the system are designed and calculated,at the same time,the double closed-loop control system of PWM inverter is designed and simulated.Finally this paper tests and analyses the application of internal feedback chopper cascade speed control system in pump,it prove that the speed control system has excellent energy saving effect,and excellent economic benefits.