Studies On The Variable Speed Wind Turbine Control System Based On PSCAD/EMTDC

A Variable speed wind turbine (VSWT) based on Doubly Fed Induction Generator (DFIG) has a complicated control system, which causes that the VSWT has some advantages and better integration characteristics by comparing with Fixed speed wind turbine (FSWT). On the basis of existing wind turbine models in the model library of PACAD/EMTDC, the whole control system of VSWT is built using PSCAD/EMTDC, and verified according to the control objective. The contents of this paper are as follows:(1) As a basis of the study, the modeling method of wind turbine components and the characteristics of doubly fed induction generator are described firstly, in order to study the electrical performance of grid-connected wind turbine.(2) Aiming to the control objective of rotor-side converter, grid-side converter and DC-link, the mathematical model of the control system is derived using vector-control principle.(3) According to the performance criterion, the PI series correction is employed to design the whole control system of the VSWT, and based on the requirements of constant power factor control mode, the control strategy of VSWT is presented.(4) According to the control objective and operating performance of the VSWT, the rotor-side converter control system, the grid-side converter control system, the DC-link control system and the ability of VSWT model tracking the wind turbine optimum operation points are verified.(5) Based on the same example system, the faulty current contribution of the synchronous generator, FSWT and VSWT are analyzed during a short circuit fault. The effect of crow-bar protection on the short circuit current is also analyzed.