Research On Variable Frequency Speed Regulating System For Vector Control Based On Three-level Inverter

Variable Frequency Speed Regulating is widely used because of its excellent in starting, speed regulation, and braking, as well as energy conservation, the technique of low voltage Variable Frequency Speed Regulating is fairly well, but when applying it's technology to high voltage, large power field, the performance is not very good and should be improved, because of the lack of power device and limited of insulation rate, the structure and control methods are very complex, furthermore, the cost is very high, another disadvantage is the power factor of system is very low, and it results in the distortion of power grid. During these several years, more and more research has been done in multilevel inverter and proposed several topologies of multilevel inverter. Lots of them have been put into practice. There are several advantages when compared with traditional two-levelpower inverter. The smaller voltage steps lead to the production of higher power quality waveforms and lower the dv/dt stresses on the load, also reducing the electromagnetic compatibility (EMC) concerns. So, in this paper; firstly, we give a summary knowledge of variety topologies of multilevel inverters, and then do some deep research with Diode-Clamped three level inverter and its application in AC driving.Firstly, this paper introduces the asynchronous motor model, and studies the SVPWM in details. This paper set up the simulation model based on FOC principle. The simulation results verify that the asynchronous motor's dynamic and steady state performances and speed modulation are excellent.The design of flux observer is the key factor for vector control. A rotor flux observer based on the estimation of the rotor resistance is designed, which combines the theory of state observer an the model reference adaptive control with the popov hyperstatic theorem. The simulation results illustrate that the adaptive rotor flux observer has many advantages such as fast identification speed and high identification accuracy. In this paper, the measurement principles of torque and rotor speed were analysed. A measuring system of torque and rotor speed based on virtual instrument was designed, which can be used to measure toque and rotor speed conveniently and accurately. The system can quickly show the dynamic and static characteristics of motor's operating state and describes directly with the graph form.Lastly, the feasibility of Variable Frequency Speed Regulating system for vector control has been proven by the laboratory experiments.