| The method, stator flux orientation vector control, not only can improve the robustness of control system, but also can overcome the influence of bang-bang control to DTC in low speed range. The harmonics of three-level inverter are less than the traditional two-level inverter's, and it is convenient to realize high sinusoidal voltage output. The maximum voltage strength which each electric component bears is small, and it is easy for three-level inverter to realize large capacity. The research on the asynchronous motor stator flux orientation vector control based on the three-level inverter is one novel work.In this thesis, the basic field-oriented control principle is presented first and the basic equetions are deduced. From this we find that the ccurrent not completely decoupling. At last, we find a decoupling method. The DC drift and initial problems of pure integrator were overcomed by using a novel integration method. A stator flux estimator can not only observe parameter, but also observe speed based MRAS is designed. Simulation results show that the method is feasible and effective.The neutral potential imbalance is an inherent problem of three-level topological structure. This paper presents the voltage balance method based on a hysteresis loop control to solve the problem. The method dynamically controls two capacitor voltage, according to the load current direction of different combinations, adjusts the small redundant vectors , fully considers the medium vectors of impact on the neutral point potential balance. This method is good at restraining the neutral-point ripple. Through the simulation in MATLAB, the correctness and feasibility of the given control scheme was verified.The main-circuit of three-level inverter and the control circuits based on DSP are designed. A set of low power three-level inverter is accomplished for the experiments. Software design and how to realize the three-level speed sensorless vector control method are described. |
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