Research On Low Voltage Traverse Of Doubly - Fed Fan Based On PSCAD / EMTDC

In the background of the global energy crisis and the vigorous supports to the new energy industry, wind power becomes a research focus in today’s world. With the increase of the capacity of wind power generation system connected to the grid, the proportion of the wind power in power system is also growing, and the characteristics of the wind turbine while faults occur become more and more significant to the grid. When the external power grid transient voltage fluctuations, the wind turbines’ability to maintain connected to grid will be a vital role in the stability of the system. When the voltage sags caused by the grid’s fault, if the wind turbines are off-grid by a large scale, it will bring secondary impacts to the weakly grid which is in fault or even voltage collapse and greater challenges to the safe and stable operation of power system. Therefore, it is very important to improve the uninterrupted operation of the wind turbine capacity when the grid’s voltage sags.In this thesis we’ll study the wind turbine’s fault ride-through capability with doubly-fed wind power generation system. At first, we gave a detailed analysis of the basic working principle of the doubly-fed wind power generation system, established a mathematical model of static ABC coordinate system and synchronous rotating d-q coordinate system, designed the back-to-back PWM converter control strategy and achieved in the PSCAD/EMTDC platform. Then it established on the basis of the transient mathematical model of doubly-fed wind power generator in the steady state mathematical model by the Laplace positive and negative transformation, combining theory and the simulation analysis of the feasibility of doubly-fed induction generator ’low voltage ride-through. And then it analyzes the influence of the short circuit current to the rotor between the before fault clearance and after fault clearance removal protection, the removal of protection before fault clearance can make active power faster recover to the rated output. Removal protection after fault clearance, the wind power generation need to absorb a large number of reactive power from the grid,this is not conducive to the grid voltage recovery. Researches show that, it is to realize low voltage ride-through by adding auxiliary circuit is required. Rotor crowbar protection before fault clearance removal of the rotor and the impact of the current transformer is smaller, more conducive to quickly return to normal operation and rapid recovery and node voltage.