风电多端柔性直流并网系统交流送出线故障短路电流解析

Short-circuit Fault Current Analysis of AC Transmission Line of MMC-MTDC System for Wind Power Intergration

随着海上风电的发展和区域风电装机容量的增大,规模化新能源电源通过多端柔性直流(MMC-MTDC)并网成为风电并网的一种趋势。然而,考虑MMC-MTDC和永磁风机构成的多换流器系统协调故障穿越及其故障特征解析尚未得到有效解决,亟待针对性研究。文中首先对传统风电MMC-MTDC并网系统故障穿越策略进行优化,给出了可行的穿越策略。进而结合多个换流器各自故障的解析,利用换流器与永磁风机换流器之间功率传输平衡原则,提出了能够全面反映风电MMC-MTDC并网系统交流故障特征的稳态短路电流解析表达式,解决了多换流器级联故障特征难以解析的问题。最后,基于实际工程参数在PSCAD/EMTDC仿真平台进行建模,仿真结果验证了所提故障穿越控制的有效性和稳态短路电流计算式的正确性。

With the development of offshore wind power and the increase of installed capacity of regional wind power, large-scale renewable energy sources are intergrated to the grid with modular multilevel converter based multi-terminal direct current(MMCMTDC), which has become a trend of wind power grid intergration. However, the fault ride-through coordination of the multiconverter system with MMC-MTDC and permanent magnet generator and its fault characteristic analysis have not been effectively resolved, thus needing urgent research. First, the traditional fault ride-through strategy of MMC-MTDC system intergrated wind power is optimized in this paper, and a feasible ride-through strategy is put forward. Furthermore, combined with the respective fault analysis of multiple converters, the principle of power transmission balance between converters and permanent magnet generator converters is used to propose an analytical expression of steady-state short-circuit current, which can fully reflect the AC fault characteristics of the MMC-MTDC system intergrated wind power. The problem that the fault characteristics of the cascaded multi-converter are difficult to analyze is solved. Finally, based on the actual engineering parameters, modeling is carried out on the PSCAD/EMTDC simulation platform, and the simulation results verify the effectiveness of the proposed fault ride-through control and the correctness of the steady-state short-circuit current calculation formula.