Cracks are one of the hidden dangers in concrete dams. The study on safety monitoring models of concrete dam cracks has always been difficult. Using the parametric statistical model of safety monitoring of cracks in concrete dams, with the help of the semi-parametric statistical theory, and considering the abnormal behaviors of these cracks, the semi-parametric statistical model of safety monitoring of concrete dam cracks is established to overcome the limitation of the parametric model in expressing the objective model. Previous projects show that the semi-parametric statistical model has a stronger fitting effect and has a better explanation for cracks in concrete dams than the parametric statistical model. However, when used for forecast, the forecast capability of the semi-parametric statistical model is equivalent to that of the parametric statistical model. The modeling of the semi-parametric statistical model is simple, has a reasonable principle, and has a strong practicality, with a good application prospect in the actual project.

No abstract

With the increasing of wind penetration in power systems, many national grid codes demand complete models and simulation studies under different system conditions in order to ensure that the connection of a wind farm would not have a detrimental impact on the grid . It is now recognized that doubly fed induction generators (DFIG) are used in many large farms. A systematic control methodology for connection of wind-turbinedriven DFIGs to the grid is presented in this paper. The purpose is to optimize control and enhance performance doubly fed induction generator wind power system by using double-vectorpwm control. The control strategies of DFIG under vector control in stator flux orientation of rotor side converter and vector control of grid side PWM converter are investigated. A dynamic model of the DFIG wind turbine is derived to develop a vector controller to decouple dynamically active and reactive power control ,and keep the DC link voltage stable, and supply low distortion currents both in the machine rotor and the supply grid. The simulations confirm the response of the DFIG independent of speed and dynamic performance of the complete system. The model is suitable to be used in a wind farm and the network under various system disturbances .