多电平柔性直流输电在风电接入中的应用

Multilevel VSC-HVDC Applied in Wind Power Integration

大规模风电的发展和集中接入对输电技术提出了更高的要求,为此,基于d-q矢量定向直接电流控制,提出了一种柔性直流输电(VSC-HVDC)的有功功率控制策略,使柔性直流输电系统能实时调整输送功率的大小并保持风电场的稳定。在考虑风速波动和电网故障的情况下,对柔性直流输电和交流输电2种接入方式进行了分析比较。在PSCAD/EMTDC软件下对所提出的控制方法和2种接入方式进行建模和仿真。结果表明:当风速发生波动时,柔性直流输电两端公共连接点处的电压和受端直流电压都能控制在参考值上,输电功率与风电出力一致,送端直流电压随功率的波动而变化。与交流输电相比,柔性直流输电能将风电场电压更有效地控制在参考值上,发生故障时能有效稳定风电场的电压与频率。

Higher transmission technology is needed to meet requirements of the development of large-scale wind power and its concentrated integration.Therefore,on the basis of the d-q vector orientated direct current control,we proposed an active power control strategy for voltage-source-converter high-voltage direct-current（VSC-HVDC） transmission that made the VSC-HVDC to adjust the transmission power real-timely and to keep the wind farm stable.Taking wind fluctuation and grid faults into consideration,we compared and analyzed AC transmission and VSC-HVDC schemes,and simulated the control strategy and both connection schemes by the software PSCAD/EMTDC.The simulative results show that the voltages of point of common coupling（PCC） and the DC voltage of receiving end can be both controlled as their reference values,and that the transmission power is consistent with wind power,meanwhile,the DC voltage of sending end changes according to power fluctuates.Compared with AC transmission,VSC-HVDC schemes appear to be more effective in controlling the voltage of wind farms at the reference value and stabilizing the voltage and frequency of wind farms during instant faults.