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An improved DC voltage droop control for interconnection of wind farms by VSC-MTDC

The strategy can ensure the rapid distribution of wind power variation, at the same time it can control the DC voltage within an allowable range. In addition, if the wind power remained stable over a period of time, the strategy can adjust the DC voltage back to the rated value. | Journal of Automation and Control Engineering Vol. 4, No. 2, April 2016 An Improved DC Voltage Droop Control for Interconnection of Wind Farms by VSC-MTDC Haibo Zhang and Zhichang Yuan Department of Electrical Engineering, Tsinghua University, Beijing, China Email: {zhanghb-13, yuanzc}@mails.tsinghua.edu.cn Yuming Zhao, Guowei Liu, and Senjing Yao Shenzhen Power Supply Company, Guangdong Shenzhen, China Abstract—According to the VSC-MTDC for interconnection of wind farms, an improved DC voltage droop control strategy was proposed. Under this control strategy, the system can automatically modify the power reference value on DC voltage –active power characteristic curve of the VSC station which was connected with the active AC network, realizing the translation of the droop curve. The strategy can ensure the rapid distribution of wind power variation, at the same time it can control the DC voltage within an allowable range. In addition, if the wind power remained stable over a period of time, the strategy can adjust the DC voltage back to the rated value. Finally, taking a typical five-terminal DC transmission system for example, simulation was processed with EMTDC/PSCAD to verify the correctness of the control strategy. The results show that the proposed strategy is suitable for interconnection by VSC-MTDC of wind farms whose flow changes frequently. Index Terms—wind farms, voltage source converter (VSC), multi-terminal DC (MTDC), DC voltage droop control I. INTRODUCTION In the 21st century, energy has become a strong driving force to promote the rapid development of human society. Coal, oil and other fossil fuels are becoming rarer, meanwhile, wind, solar and other renewable energy sources have got extensive attention and vigorous development from the international community. As a kind of renewable and clean energy, wind power has abundant resources and the construction of large-scale offshore wind farms has become an important aspect of wind energy .