Direct Torque Control Of Open-end Winding Induction Motor Based On Single Supply Anddual Three-level Inverter System

Multilevel inverter is mainly applied in high voltage large capacity situation. It plays a significant role in saving energy and reducing consumption as well as improving the control performance. The double side power supply topology of single supply and dual three-level inverter adopted overcomes the limitation of voltage and obtains high output voltage with lower stress level of power switch device. In that case it has the same ability with five-level inverter output voltage, and has the advantage of multilevel inverter technology.Based on open-end winding induction motor system of single supply and dual three-level inverter, this thesis studies open-end winding induction motor mathematical model, simulation model, no common-mode voltage vector SVPWM control strategy, neutral-point potential balance control strategy and direct torque control system.Open-end winding induction motor mathematical model is established based on the structural feature and circuit model of motor, and then the simulation model of openend winding induction motor is set up. With double side power supply topology of single supply and dual three-level inverter for open-end winding induction motor, no common-mode voltage vector SVPWM control strategy is studied. Through the analysis of no common-mode voltage vectors option, the judgment of the reference voltage vector position and the voltage vector function time distribution, it can restrain the common-mode voltage of the system. Based on the principle of neutral-point potential balance with single supply and dual three-level inverter, and analysis of different types with no common-mode voltage vector to the neutral-point potential balance the neutral-point potential balance factor is introduced to choose the vector type and function time, so that the neutral-point potential balance control can be achieved. It is applied to the open-end winding induction motor system of single supply and dual three-level inverter by combination of direct torque control technology and the SVPWM control strategy with no common-mode voltage vector. Through the analysis of the stator flux observer design and the voltage vector calculation model, it can be achieved that direct torque control of open-end winding motor, and improved the dynamic performance of the system.Based on theoretical analysis of no common-mode voltage vector SVPWM control strategy, neutral-point potential balance control strategy and direct torque control system the simulation model is set up and effectively verifies the analysis results in view of open-end winding induction motor system of single supply and dual three-level inverter. The simulation results proved the feasibility and effectiveness of the control strategy for open-end winding induction motor system of single supply and dual threelevel inverter.