Research On Speed Control System Of Electrically Excited Synchronous Motor

With the development of modern power electronics technology, microcomputer control technology and large-scale integrated circuits. Electrically excited synchronous motor is widely applied in the field of electric drive, because of its advantages of high efficiency, strong overload capability and adjustable power factor This thesis takes the speed control system of electrically excited synchronous motor as the research object, studies and analyzes on the air gap flux-oriented FOC control system and the state observer and so on.In this thesis, the electrically excited synchronous motor is drived by the NPC three- level voltage source type converter. Therefore, this thesis studies the principle and realization method of three- level inverter. In view of the inverter output voltage harmonic content problem, a voltage reconstruction method for detecting the motor phase voltage is presented. For the neutral voltage imbalance of NPC three- level inverter, this thesis analyzes the reasons of the imbalance, and presents a method by changing the action time of small vectors to realize the control of neutral voltage balance.This thesis, which is based on coordinate transformation and vector control theory, deduces the mathematical model of electrically excited synchronous motor in static coordinate system and rotating coordinate system, and analyzes the basic principle of the air gap flux-oriented control of electrically excited synchronous motor. Adopting typical type I system and typical type II system to deduce the transfer function and design the controller parameters based on the air gap flux-oriented control of FOC control system of each loop. And discuss the stator current loop before and after the MT axis decoupling. By building simulation model, the designed loops are analyzed.The accurate acquisition of flux is one of the cores of vector control and speed observation. In this paper, combining the mathematical model of electrically excited synchronous motor with the modern control theory knowledge, presents the flux state observer. Flux state observer can be divided into reduced-order observer and full-order observer, both took the form of refactoring to obtain motor flux. By combining the flux state observer with MRAS, the model reference adaptive method observer based on state observer is presented. This method which is based on the model reference adaptive principle, adopts the motor itself as the reference model and the state observer as the adjustable model to realize the speed estimation.Based on the existing resources in the labo ratory, we establish the experimental platform of electrically excited synchronous motor speed regulation control system based on three- level NPC inverter. The main circuit components selection and the control algorithm are completed, relevant theories are verified by experimentation.