The Research Of Indirect Torque Control And Indirect Power Control Strategy Of Brushless Doubly-fed Machine

The brushless doubly-fed machine is a new kind of AC motor. Its structure is similar to the structure of cage rotor asynchronous motor, there is no carbon brush slip in it, and it can be operated in the way of doubly-fed. It could not only operates as electromotor in AC speed control system, but also could operates as generator in variable speed and constant frequency electric system. It has the characteristics of small capacity of frequency inverter and adjustable power factor. It has broad application prospect in field of wind generators, pumps control energy-saving system and VSCF wind power especially. In recent years, ontology design method of brushless doubly-fed machine improves constantly, efficiency and harmonic problem puzzled domestic and foreign scholars for many years has a breakthrough, control method become a research hotspot. The essay focuses on the study of brushless doubly-fed machine indirect torque control and indirect power control strategy, the research content completed is as follows:1. The mathematical model of multi-circuit of brushless doubly-fed machine, the d-q rotor speed model and the model of double static coordinates proposed by our group is deeply studied, which laid a theoretical foundation for the building of the subsequent simulation model and experiment.2. An improved orthogonal nonlinear feedback compensation flux observation method is proposed as the power winding flux linkage observation method, and the method and the new type error free voltage model flux observation method are respectively adopted as the control winding and power winding of brushless doubly-fed machine. Theoretical analysis and prototype experimental results show that both kinds of flux observation method can effectively eliminate the u-i model integrating drift, the inaccurate flux observation problem when extremely low frequency operating is solved, and compared with the research of the existing research results, the steady-state and dynamic performance of indirect torque control system of brushless doubly-fed motor when control winding frequency is close to zero can still maintain well.3. Adjustable reactive power is one of the important advantages of induction motor relative to the brushless doubly-fed machine. Power generation is the basic performance for brushless doubly-fed machine. In view of indirect torque control system of the double-fed brushless machine with reactive power control function, the existed achievements of research group is completed. The experimental results show that the system can achieve speed regulating from super-synchronous to sub-synchronous under the condition of reactive power at a given constant, and when cross synchronous speed, the system operates stable; the regulating function from perceptual reactive power to the capacitive reactive power on the condition of constant speed is achieved, and the system has good steady and dynamic performance.4. A kind of indirect power control strategy of brushless doubly-fed machine is put forward; the system structure diagram is constructed. Compared with the indirect torque control, this control method is more suitable for the brushless doubly-fed machine operating under the state of generate electricity, active power and reactive power of the power winding are chose as control target in The control strategy, active and reactive power control are realized in double stationary coordinate system without rotating coordinate transformation, the system has advantages of simple structure and strong robustness to motor parameters, simulation model of Indirect power control system is established with wind turbine as the prime mover, the simulation results show that the system has realized the maximum power tracking of the wind energy, reactive power is adjustable, the feasibility of this control strategy is proved. Grid-tied, variable speed constant frequency and active power adjustment experiment of brushless doubly-fed generator is completed in Laboratory condition, experimental results preliminarily show the feasibility of indirect power control strategy.5. The hardware of control system of brushless motor is designed, which include the main circuit and control circuit. The main circuit includes the choice of power components and parameters; control circuit includes DSP minimum circuit, sampling circuit, communication circuit and position detection, etc.; a lot of work Focused on reliability, protection function, versatility, scalability and anti-interference ability of system is conducted. The hardware system Developed has compact structure, meet the demand of experiment.6. The above research contents are programmed and realized the on brushless doubly-fed machine experimental platform based on DSP TMS320LF2407A in the laboratory.