The Research On DC Interconnection Of Wind Farm

In recent years, the rapid development of wind power generation technology, and its power generating capacity accounts for the proportion in the whole power increasing, large scale and large capacity wind farm internal operation and grid technology will become the future of wind power field research focus.In this paper, on the basis of the permanent magnet direct drive wind turbine, combined with the relevant technologies of dc grid, and puts forward a method of DC wind farm interconnection, i.e., the motor output power after rectification into the DC bus, the DC bus voltage DC booster station rises to be used for voltage rating of HVDC transmission and transportation, and then the DC the access grid inverter power. This article will discuss respectively from the motor control, converter control, DC voltage control and wind farm energy management aspects, and through the simulation software to verify the research results.In addition, this paper introduces the topology of DC wind farm interconnected and proposed a new topological structure of wind farm based on the technology of dc interconnection topology suitable for offshore wind farm, carrying on the detailed elaboration of the innovation of the structure proposed. Meanwhile, it summarizes the main current mode of grid connected wind farm, and in contrast to explain the efficiency, cost and feasibility and other aspects of the proposed topology as well as demonstrates the proposed topologies with optimized properties.Besides, basic theory of MMC modular multilevel in the application of DC interconnected wind farm is introduced, using recent level approximation method to design a high power one-way DC-DC converter based on MMC, and analyze the topological structure which is given.The control strategy of PMSG and DC converter is described. Among them, the strategy of PMSG includes a fan control, pitch control, and machine side converter control. In this paper,the mathematical model is derived firstly, and then makes the appropriate control strategies based on mathematical models introduced to make a control block diagram, and make a summary of the entire control strategy of large-scale wind farms.Lastly, using DigSILENT/Powerfactory simulation platform, the aforementioned control strategy into the simulation model and debugging. And the simulation results of the wind generator output active power, the reactive power exchange, stator voltage, DC bus are studied in this article. By changing the size of wind speed, the size of the reactive power demand, and setting up three phase short circuit fault and other ways to verify the feasibility of control strategy, but also verify the wind farm can realize stable electric energy output in the structure and control mode.