| Currently the main fatigue test method for wind turbine blades at home and abroad is single-excitation fatigue loading, but the method has the problems of the big moment distribution precision error and the shortage of system driving ability. Therefore, dual-excitation fatigue loading method was adopted in this paper. During the process of dual-excitation fatigue loading, the two loading sources and the blade were not in the same plane because of a certain torsion angle in blade oriented direction, thus forming a complex nonlinear strong coupling system. In order to improve the accuracy of the fatigue test, it is necessary to study the influence of coupling effect on resonance, and a synchronous control strategy must be studied to reduce the impact of the coupling effect. Therefore, the main research results of this paper are as follows:First of all, the mathematical model and simulation model of dual-excitation fatigue loading system were built, and the impact of coupling effect on the system vibration was simulated. Combined with the state equation of three-phase asynchronous motor in two-phase synchronous rotating coordinate system, the mathematical model of dual-excitation fatigue loading system was established using Lagrange equation modeling method. Simulink dynamic simulation model was established according to the mathematical model, and simulation test was carried out under certain simulation parameters. The simulation results showed that coupling effect affected speed synchronization and phase synchronization of the two loading sources and made the system difficult to achieve resonance state.Secondly, in order to eliminate the impact of the coupling effect on system vibration, the speed synchronization control scheme and the phase synchronization control scheme were developed, and the control algorithm was designed. Speed synchronization used parallel speed synchronization control scheme of synchronization error feedback based on reference speed. Sliding mode variable structure following error synchronous control algorithm was designed to reduce the following error of the two loading sources, and stability analysis was made using Lyapunov function. Synchronization error control algorithm based on PID control was developed to reduce synchronization error. Phase synchronization used phase synchronization control scheme of virtual axis method, and virtual loading source- error segmentation intelligent control algorithm was designed. The algorithm took advantage of PID control and fuzzy control, and system had high control precision and good robustness. The above algorithm was added to the simulation model in the second chapter, and the simulation results showed that the decoupling effect of the designed synchronization control algorithm was good.In order to validate the coupling effect and effectiveness of decoupling algorithm, dual-excitation fatigue loading test platform for LZ37.5-1.5MW wind turbine blade was set up. Fatigue tests were carried out under natural state and decoupling algorithm control respectively. Test results under natural state were consistent with the simulation results in second chapter, which verified the correctness of the mathematical model and simulation model; Test results under decoupling algorithm control were in accordance with the simulation results in the third chapter, verifying the good decoupling effect of synchronization control algorithm. Meanwhile, the algorithm can guarantee speed synchronization and phase synchronization of the two loading sources and make the system achieve resonance state.Finally, According to the requrrements of dual-excitation fatigue loading system, the visual man-machine interface was developed based on LabVIEW software. The interface not only had characteristics of modular, automation, but also acquired and stored information real-timely, such as speed and phase of the two loading sources, blade amplitude, vibration times and so on. |
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