Study On Dual Three-level Vector Control System Of Electrically Excited Synchronous Motor And Its Application

With more and more serious energy crisis and the requirement of energy saving and emission reduction in our country, the high-power drive equipment is urgently required to be upgraded. Electrically excited synchronous motors are widely used in a lot of large equipment drive systems because of their advantages, such as strong overload capacity, high efficiency and adjustable power factor, etc. Dual three-level vector control system of high-performance electrically excited synchronous motor can simultaneously realize both energy-saving speed regulation and environment protection. For this reason, the research and development of this system has significant social effect and economic value.In this thesis, dual three-level electrically excited synchronous motor with air-gap flux oriented vector control system is studied. Based on the three-level space-vector pulse width modulation (SVPWM) algorithm with reference voltage translation, a strategy of balancing the neutral-point potential self-adaption unification algorithm for four-quadrant operation dual three-level converters is introduced, and the three-level pulse width modulation (PWM) rectifier virtual stator flux oriented control strategy is proposed. In addition, the virtual stator flux observer model in d ? qcoordinate system is used. Meanwhile, the reactive current control strategy on grid-side is proposed. The saturation mathematical model of salient pole synchronous motor base on q axis conversion idea is proposed, and then the closed-loop hybrid air-gap flux estimator model considering saturation effect is proposed on these basis. Besides, the salient effect and armature reaction of electrically excited synchronous motor effects the system is analyzed and the control strategy of the rotor field current and the stator exciting current in arbitrary rotation coordinate system is proposed. Due to inconvenience and drawback caused by the encoder used in special occasions, the electrically excited synchronous motor sensorless strategy is proposed.