Research On PMSM Drive Used On Wind Turbine Electric Pitch

As a non-polluting renewable energy, wind energy is of great value. The major challenge faced by modern wind turbine technology is how to further enhance efficiency, increase strength and reduce costs. So an in-depth study is carried out in the world. According to the latest survey, the world's largest wind turbine suppliers are using electric variable pitch as the structure of the variable pitch system. Variable pitch speed mode refers to the use of control technology and power system, changes the pitch angle of the blade size installed in the large-scale of the wind turbine wheel, so as to change the aerodynamic characteristics of the leaves, so that the blades and force the whole situation has been greatly improved.The operating principle of electric pitch system of megawatt wind turbine is introduced in this paper, and three-phase permanent magnet synchronous motor (PMSM) is chosen as the executive motor of the proposed system. Based on the analysis on the operating principle of electric pitch and the control strategy of servo driver, an electric pitch control system composed of a PMSM and its servo-driver is designed.The PMSM is modeled in the d-q reference frame fixed to the rotor based on field-oriented technique, and vector control is applied and implemented. Various sensorless schemes are reported among which there are two major approaches for their execution. One is based on the back electromotive force estimation technique. The typical methods followed here are sensorless drives using the voltage model of the motor, a flux linkage calculation, model reference adaptive system, observers, extended Kalman filter and parameters estimation. Another approach is based on the measurement of inductance or current response which is rotor-angle dependent. An initial rotor position estimation method is proposed on the PMSM which is based on inductor saturation effect. The proposed method estimates rotor position by the phase angle of the short-circuit current vector and rotor speed by the derivative of each phase angle of current vectors among the short-circuit durations based on SVPWM. Based on the mathematical model of the PMSM, through discussing the principle of flux-weakening control, it is proposed that a novel method for PMSM control strategy based on current tracking, which effectively broadens the speed ratio under lower voltage limitation and constant power. In Psim, two control loops are used to build up the control strategy, which are the inner current-loop and the outer speed-loop. Speed overshoot is eliminated through two loops with negative differential feedbacks ensuring rapid speed response. The simulation result verifies the validity and the feasibility of the control strategy, and it also has high control precision, fast response and robustness.