Reactive Coordination Control Strategy Of Dfig Wind Farm Considering Network-loss Of Collection System

With the increasing maturity of the wind turbine manufacturing technology, wind turbine unit capacity and the wind farm installed capacity is more and more big. Grid connected wind power brings serious challenges to the security of the power grid connected to the power grid. Among them, the typical reactive power control problems, such as the low voltage of point of common coupling and high network-loss of power collection system in DFIG-based wind farms, are particularly prominent. At present, the doubly fed wind turbine with its variable speed constant frequency, active/reactive power decoupling control and a low cost investment takes up a significant market share. However, in order to pursue maximum economic benefit, wind turbine manufacturers did not make full use of reactive power regulation capabilities of doubly-fed wind turbine. Therefore, the study of reactive regulation ability for the doubly fed wind turbine and reasonable control of doubly fed wind turbine output reactive power has important significance for improving the voltage level of point of common coupling and reducing network loss of power system.In this paper, the power relationships between the various parts of the doubly fed wind turbine is analyzed and the mathematical model of the doubly fed wind turbine is built up. Based on this, we study the reactive power regulation capability of the doubly fed wind turbine which is restricted by the grid side converter. According to the actual operating parameters of the wind turbine, the reactive power regulation capability of the actual wind turbine in different active power output was analyzed. In view of the long distance of feeder for doubly fed wind farm collector systems, the wind turbine pitch is far and high network-loss of power collection system in DFIG-based wind farms. The reactive power regulation ability of doubly fed wind farm considering the loss of collector system is analyzed.Secondly, in view of the traditional method to calculate the reactive power demand cannot accurately adjust the voltage of point of common coupling to the reference value, this paper proposed a double adjusting method to calculate the reactive power demand of the doubly fed wind farm. In view of the existing double fed wind farm does not make full use of the doubly fed wind turbine power regulation ability, this paper presents a reactive power control strategy. In this paper, the position of reactive power output of wind turbine generator is determined by the reactive power sensitivity of collector system, and the reactive power output capacity of doubly fed wind power generator optimized by genetic algorithm.Finally, a mathematical model is built based on the grid structure of a real double fed wind farm in the northeast of China in this paper. According to the actual operation data, this paper analysis the reactive power regulation ability, reactive power demand, the network-loss/reactive sensitivity and voltage/reactive sensitivity, determined the position of the wind turbine which output reactive power, optimized the DFIG reactive power output capacity by genetic algorithm. The case shows that the control strategy can improve the point voltage level and reduce the loss of the collection system.