Abstract

The paper established a whole mathematical model of variable speed constant frequency (VSCF) brush-less doubly-fed wind power generation system, analyzed the relationship between BDFIG maximum absorption power and speed, and proposed direct torque control strategy to achieve brushless doubly-fed wind power generation VSCF machine control. With double-loop control of torque and magnetic chain and based on the change of wind speed, the system took the theoretical optimum speed value of wind turbine absorption maximum power point as the direct torque control speed reference and obtained torque reference by the PI regulator; and obtained a given flux by making the reactive power through power windings zero on the principle of maximum power factor. Based on the characteristic of brushless doubly-fed induction generator, the paper gives the method of indirect calculation for estimated torque and u-i model for flux estimation. Two ways of direct torque control performance, wind mutations and wind speed gradients, are simulated, which could reach a conclusion that the wind turbine will run at the optimal tip speed ratio and response faster by directly controlling the electromagnetic torque of the generator, thus achieving maximum wind energy capture and enhancing the power generation efficiency.

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