| Brushless doubly fed machine (BDFM) is a new type of AC adjustable-speed motor with simple and stable structure, adjustable power factor, small capacity of power electronic devices, low maintenance cost and the combination characteristics of asynchronous and synchronous motor. Especially suitable for variable frequency drive system and variable speed constant frequency wind power system.The development status of wind power and its value in future were expounded according to sustainable development of energy and society. Considering the complexity of wind power generation system and limitation of single control algorithm, the hybrid control strategy combined with intelligent control algorithm and other advanced control algorithms was studied. The main achievement and methods were discussed in the application of maximum wind energy capture, power prediction, yaw control and other aspects.Based on BDFM structure, the principle and operation mode were analyzed. By deducing the mathematical model of BDFM abc three-phase stationary coordinate system and rotor speed d-q axis system, the Matlab/Simulink simulation model of open-loop operation were established. Simulation results show the dynamic and static characteristics of the BDFM under various operating conditions, such as single-fed, double-fed synchronous, double-fed super-synchronous and double-fed sub-synchronous.Aimed at irregular electromagnetic noise, irregular torque and rotational speed of BDFM. the nonlinear differential equations of BDFM were derived based on its d-q axis model. Taking the reciprocal of rotor time constant as control parameter, the chaos model of BDFM was constructed. By numerical simulation, the maximum Lyapunov exponent spectrum of BDFM system was obtained. The range of parameters was analyzed when the chaotic phenomenon emerged in BDFM and the simulation results of chaotic motion were verified in Matlab environment.Based on the passivity theory, brushless doubly-fed wind power generator (BDFG) control system was researched from the perspective of energy. The α-β two-phase static axis equations of the BDFG voltage were derived and the Euler-Lagrange model of BDFG was constructed. Based on this model, the variable damping passivity-based speed control system was designed, which would trail a desired speed when the system running below rated wind speed. Contrasting with vector control and constant damping on Matlab/Simulink platform, the simulation results proved the feasibility and effectiveness of variable damping passive control and its better robustness and dynamic performance. |
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