Abstract
In the case of the stiffness of offshore wind turbine blade is relatively large, the joint excitation device solves the problem of low accuracy of bending moment distribution, insufficient driving ability and long fatigue test period in single-point loading. In order to study the synchronous characteristics of joint excitation system, avoid blade vibration disturbance. First, on the base of a Lagrange equation, a mathematical model of combined excitation is formulated, and a numerical analysis of vibration synchronization is performed. Then, the model is constructed via MATLAB/Simulink, and the effect of the phase difference on the vibration synchronization characteristics is obtained visually. Finally, a set of joint excitation platform for the fatigue test of offshore wind turbine blades are built. The parameter measurement scheme is given and the correctness of the joint excitation synchronization in the simulation model is verified. The results show that when the rotational speed difference is 2 r/min, 30 r/min, the phase difference is 0, π/20, π/8 and π/4, as the rotational speed difference and the phase difference increase, the time required for the blade to reach a steady state is longer. When the phase difference is too large, the electromechanical coupling can no longer make the joint excitation device appear self-synchronizing phenomenon, so that the value of the phase difference develops toward a fixed value (not equal to 0), and the blade vibration disorder is serious, at this time, the effect of electromechanical coupling must be eliminated. The research results provide theoretical basis for the subsequent decoupling control algorithm and synchronization control strategy, and have good application value.
Highlights
Offshore wind power is widely valued by all countries for its advantages of strong wind resource stability, reducing noise pollution and saving land resources
(2) Through the theoretical analysis and experimental verification, it is concluded that the rotational speed difference and the phase difference are the key parameters that affect the vibration synchronization of the joint excitation device
When the initial speed difference and the phase difference are small, joint excitation devices can eventually rely on their own electromechanical coupling tends to be synchronized, and the greater the initial phase difference, the longer it takes time to reach the synchronized vibration state
Summary
Offshore wind power is widely valued by all countries for its advantages of strong wind resource stability, reducing noise pollution and saving land resources. Liao Gaohua et al.[11,12,13] built the dynamics model of the biaxial fatigue loading system for the wind turbine blades test, and provided multiaxial fatigue loading can make the load in the sections of wind turbine blade to approach the real fatigue load condition They used the Lagrange equation and energy distribution method to analyze the coupling laws of excited system at various frequencies. Pan Zujin et al.[16] analyze the relationship between the excitation force, damping, and the amplitude variation of the blade by the Lagrange equation the finite element simulation method, and proved that multi-point excitation could better fit the fatigue damage distribution It can be seen from the above that the joint excitation can well simulate the actual load on the offshore wind turbine blades. We built a set of joint excitation test device to verify the correctness of mathematical and simulation model, and get a complete coupling and synchronizing mechanism of wind turbine blade joint excitation device, which lay a theoretical foundation for the subsequent decoupling algorithm and program design of synchronous control strategy
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