Qin Shiyao

A new method of wind turbines modeling based on combined simulation

Wind power has reached a significant penetration level in the power system worldwide. Grid codes are proposed to safe guard power system with large scale wind power integration. To verify grid code compliance, wind turbine integration characteristics should be verified based on test and simulation results. Therefore, accurate simulation model need to be developed. Since wind turbine model are generally developed to fulfill specific purpose, there are three categories as follow: electromechanical transient model for the study of wind power integration in power system; electromagnetic transient model for the purpose of analyzing wind turbine electrical transient characteristics; and model used to vindicate wind turbine design and control strategy concerning load calculation, mechanical dynamic analyzing etc. However, neither of these models aims at analyzing the interaction between mechanical components and electrical components. This paper introduces a new method of modeling and combined simulating of aerodynamic, mechanical, control and electrical systems in two simulation software platforms. The wide used software tools GH Bladed and MATLAB/Simulink were utilized. According to the method, mechanical, aerodynamic and control (pitch control and torque control) model is specified in GH Bladed, while electrical model (concerning grid, generator and converter) was implemented in MATLAB. In the process of simulation, the two separate models were synchronized via a communication interface which was based on TCP/IP protocol. A 2.5MW wind turbine was modeled and simulated using the presented combined simulation method. Wind turbine simulation results during grid fault were verified with low voltage ride through test data to certify the accuracy of the combined simulation model. Based on the simulation results, mechanical dynamic on blades and drive train during grid fault was presented and the simulation methods further application in analyzing the interact between wind turbine and grid system was proposed.

Influence factors on low-voltage operation characteristics of large-scale wind farms

Although the low voltage ride through (LVRT) capability is no longer a difficulty for most of the existing wind turbines, the low voltage operation characteristics of different wind turbines and reactive power compensation devices varies a lot. The LVRT capability test result of a single wind turbine is not equal to the performance of a whole wind farm during gird fault, especially when the wind farm is considerably large or the grid is weak. As a result, the influence factors on the low voltage performance of large wind farms need to be studied. In this paper, electromechanical transient simulation models of doubly fed induction generator (DFIG) wind turbine and direct-driven permanent magnet synchronous generator (D-PMSG) wind turbine were built in power system simulation software DIgSILENT/PowerFactory. The accuracy of the models was validated by comparing simulation results with test results. On the basis of the validated models, a 100MW wind farm was modelled with DFIG and PMSG wind turbines respectively, and the LVRT performance was compared. The interrelationship between the control characteristics of reactive power compensation devices and the overvoltage after fault clearance was analyzed. It is concluded that, when grid fault occurs, the reactive power characteristics and the overvoltage ride through capability of wind turbines as well as the behavior of the reactive power compensation devices are important factors that may affect the LVRT capability of a wind farm.