The Research Of Control Methods On Brushless Doubly-Fed Machine

Brushless Doubly-Fed Machine (BDFM) is a new kind of machine, which can operate in asynchronous, synchronous or doubly-fed models. It can be used in AC adjustable-speed drive systems as a motor or be used in generating systems as a generator. The BDFM system has the characteristics of less capacity inverter, separately adjustable active power and reactive power, as well as power factor, continuously adjustable speed in four quadrants, and brushless operation, so it will have widely used broad applications in saving-energy-adjusting-speed systems of wind machines and pump and variable-speed-constant-frequency wind power and water power generating systems. In this thesis the operating principles and characteristics of BDFM are analyzed systematically, and the controlling principles and methods are researched deeply. The main works is as following:In the view of the air gap field of BDFM, the systematic analysis of the operating principles and the basic structures of stator and rotor, the deduction of stable equivalent circuit and equations, the discussion on the characteristics of stable performance.In the paper, according to the BDFM's request of the power bidirectional flowing, the control method for PWM rectifier is studied, and the corresponding experimental equipment, the dual-PWM inverter is designed. Based on the systematic research of the principle and mathematical model of three-phase voltage source PWM rectifier, the load current front-back control was proposed to enhance the performance of the vector decoupling control. The experimental and simulation results demonstrates that the designed PWM rectifier can meet the demands of the energy of BDFM system flowing bi-directionally and the adjustable unit power factor and have the characteristics of low harmonic contents, good dynamic performance.The network, the rotor speed models are also introduced, and the double synchronous speed mathematical model has been deduced and set up in this paper. Firstly, the double synchronous speed mathematical model is established on the basis of rotor speed model which divided BDFM into control winding and power winding sub-coordinate systems. In each coordinate system, the variations of stator and rotor are all changed into DC value, so the speed, the toque and the power can be controlled by voltage of the control winding, which founds the theoretic foundations for BDFM's control strategy and methods.In this thesis, digital simulation research of the operation performance in asynchronous, synchronous, doubly-fed and default models of BDFM are conducted. The simulation results show that (Dthe speed is only decided by the frequency of control winding under the condition of full excitation; ? the electrical energy through the control winding accounts a little components of the system, so the capacity of the inverter can be decreased efficiently ;(3) synchronous and doubly-fed models are BDFM's desired operating models;@In the doubly-fed model, BDFM shows some characteristics of synchronous machine and it can be used as common induction motor in the case that the inverter breaks down, which realizes the universality and brusshlessness.It researches the rotor flux oriented control system of BDFM, builds the power winding and control winding on separate synchronous reference frame, and orients flux separately, which simplifies the mathematical model. On the base of that the paper proposes a rotor flux oriented control strategy according to the dual-synchronous coordinate model, which can realizes the dynamic torque control. The simulation and experimental results indicate that this control method with perfect dynamic torque control performance is suitable for BDFM control system, and carries out as simply as that of the induction machine, and has perfect dynamic performance.The paper studies the active power and reactive power control system of BDFM. In the rotor speed model, the active power and reactive power control models are deduced, and a power control strategy is proposed, by dividing the voltage of the control winding into decoupling and compensation components. The simulation and experimental results show that the system with rapid dynamic response and stable operating performance can realize the independent control of the active power and reactive power.The applications of the intelligent control in BDFM systems are also discussed. The fuzzy power factor control method and the rotor flux oriented control strategy based on recursive fuzzy neural network (RFNN) controller are proposed. The simulation results show that: (D the structure of the fuzzy power factor control is simple, and the realization is convenient, which can meet the need of the power factor control; ? the rotor flux oriented control strategy based on RFNN has less trace error and more rapid convergent speed than traditional PI control. Furthermore, it reduces the effects of external disturbance by error compensation.The paper deduces BDFM's mathematical models based on analysis of the basic operation principle and stable characteristics, makes simulation research in variable...