Vector Control Of Open-End Winding Asynchronous Motor Based On A Dual Three-Level Inverter System

Multilevel inverters have been widely used in medium-voltage high powerapplications such as high power drive, active filter and ships propulsion. Relative tothe traditional two levels, multilevel inverters has many advantages in low outputvoltage harmonic content, low switching frequency, small switching loss andelectromagnetic interference. Dual three-level inverter topology has the same voltageoutput capability with a five-level inverter and the equivalent switching frequencydoubling, the output voltage is twice the single three-level inverter, and it has obviousadvantages in high frequency fields. For dual three-level inverter open-end windingasynchronous motor vector control system, its open-end winding asynchronous motormathematical model, open-end winding asynchronous motor simulation model,SVPWM control strategy, neutral-point potential control strategy and several vectorcontrol system conduct are researched.With the analysis of circuit model for open-end winding asynchronous motorwith dual power supply, the open-end winding asynchronous motor mathematicalmodel is established, and on the basis of the mathematical model the simulationmodel of the open-end winding asynchronous motor is built; based on the analysis ofprinciple for three-level inverter, the principle of dual three-level inverter topology isintroduced, with the basic principle of the line voltage coordinate SVPWM algorithm,SVPWM control of dual three-level inverter topology is achieved; for the balance ofneutral-point potential problems, the basic principle of neutral point clampedthree-level inverter midpoint potential fluctuations caused by the neutral-point currentis analyzed, and the neutral-point current expression is deduced, optimization functionis built with the principle of conservation of charge to select the optimal switchingsequence and the action time of reuse vectors; based on the basic principles of therotor flux orientation, the stator current torque component and the excitationcomponent are not completely decoupled, a decoupling controller is designed; finally,on the basis of open-end winding asynchronous induction motor model the simulationof open-end winding asynchronous induction motor vector control system isresearched.Based on the theoretical analysis of research, this thesis focuses on simulationstudy of the SVPWM control of dual three-level inverter, neutral-point potentialcontrol strategy and open-end winding asynchronous motor vector control system，and the practicality and correctness of dual three-level inverter topology are verified.