海上风电场三电平VSC-HVDC系统仿真研究

摘要

随着土地资源紧缺和海上风电成本的不断降低,海上风电开发与建设受到各国重视,且随着海上风电场规模的扩大,急需采用柔性直流输电变流器装置.这里研究了海上风电场柔性直流输电变流器拓扑结构及控制方式,其中,主电路采用中点箝位式三电平结构,通过建立该结构的等效数学模型,根据空间矢量调制算法,检测交流侧电流方向以及直流侧电容电压,控制中点电压平衡来保证电容电压平衡.采用双闭环矢量控制,风场侧控制直流电压,电网侧控制有功功率.同时,内环采用电流前馈解耦方式,分别独立控制有功、无功功率.最后,利用Matlab搭建整个系统的仿真模型,验证了所采用拓扑结构的优越性及控制方式的正确性.%With the shortage of land and the declining cost of wind power generation on the sea,offshore wind farm grows popular in more and more countries.This paper studies topology structure and control strategies of the converter. The main circuit adopts a three-level neutral point clamped structure whose equivalent mathematical model has been established.According to the space vector modulation algorithm,by testing the AC current direction and DC side capaci tor voltage,the method of midpoint voltage balance control to guarantee the balance of capacitor voltage is given.The control system adoptes double closed loop vector control strategy,in which both of converters work in step with DC voltage controlled by wind farm lateral and active power controlled by grid side.Inner loop used current feed-forward decoupling method to realize active power and reactive power independently control.Finally, simulation model is set up in Matlab, results show the topological structure advantageous and control strategies correct.