VSC-HVDC联网的海上风电系统低电压穿越技术

发布时间：2019-01-17 06:45

【摘要】：海上风电产业的蓬勃发展为解决能源危机提供了重要保障，其中基于电压源型换流器的柔性直流输电技术(Voltage Source Converter-Based HVDC, VSC-HVDC)以高效、灵活及可控性强等优势在海上风电并网和传输系统中倍受青睐。随着各国对风电并网要求的逐渐提高，VSC-HVDC系统的低电压穿越(Low Voltage Ride Through,LVRT)问题成为了国内外研究的热点。本文主要围绕海上风电VSC-HVDC系统的低电压穿越控制技术展开分析，重点研究了当电网发生深度电压跌落时的VSC-HVDC直流侧过电压和交流并网点电压凹陷问题，提出采用动态电压恢复器(Dynamic Voltage Restorer, DVR)辅助VSC-HVDC实现低电压穿越的控制方法。具体实施方案由以下两方面组成：一方面，在浅度电压跌落情况下，提出采用VSC-HVDC传统无功补偿策略，DVR处于旁路状态，风电场能够稳定运行。另一方面，当电网电压深度跌落时，单纯的无功补偿策略已不能稳定直流母线和交流并网点电压。此时，切换VSC-HVDC改进的控制策略并投入带能耗电阻的超级电容型DVR，通过DC/DC变换器控制能耗电阻和超级电容阵列吸收VSC-HVDC直流母线侧过剩能量，，以维持直流母线电压稳定；同时利用超级电容放电给DVR逆变器提供稳定的直流电源，以快速补偿电网故障电压，使岸上交流母线电压维持正常水平。此外，在故障期间由于协调控制策略具有很好的鲁棒性能，保证了风电机组的稳定运行。在MATLAB/Simulink中搭建整个海上风电场VSC-HVDC和DVR的仿真模型，并进行了三相电压深度跌落故障、三相短路故障及单相短路故障的仿真验证，结果表明该协调控制策略不仅提高了系统效率，而且在对称与不对称电压故障情况下都能体现出良好的补偿性能，对海上风电系统的可靠运行和低电压穿越能力的提高具有一定的现实意义。
[Abstract]:The booming development of offshore wind power industry provides an important guarantee to solve the energy crisis, in which the flexible direct current transmission technology (Voltage Source Converter-Based HVDC, VSC-HVDC) based on voltage source converter is highly efficient. Flexibility and controllability are very popular in offshore wind power grid and transmission system. With the increasing demand of wind power grid connection, the problem of low voltage traversing (Low Voltage Ride Through,LVRT (Low Voltage Ride Through,LVRT) in VSC-HVDC system has become a hot research topic at home and abroad. In this paper, the low-voltage traversing control technology of offshore wind power VSC-HVDC system is analyzed, and the overvoltage of VSC-HVDC DC side and the voltage sag of AC node when the power grid is in depth voltage sag are studied in this paper. A control method of low voltage traversing using dynamic voltage restorer (Dynamic Voltage Restorer, DVR) assisted VSC-HVDC is proposed. The concrete implementation scheme consists of the following two aspects: on the one hand, under the condition of shallow voltage drop, the traditional reactive power compensation strategy of VSC-HVDC is proposed, the DVR is in the bypass state, and the wind farm can operate stably. On the other hand, when the voltage depth drops, the simple reactive power compensation strategy can not stabilize the DC bus and AC node voltage. At this time, switching the improved control strategy of VSC-HVDC and putting the super capacitor DVR, with energy consumption resistance to control the energy consumption resistance and super capacitor array to absorb the excess energy of VSC-HVDC DC bus side through the DC/DC converter. To maintain DC bus voltage stability; At the same time, the supercapacitor discharge is used to provide the DVR inverter with a stable DC power supply, which can quickly compensate the fault voltage of the power grid and make the on-shore AC bus voltage maintain the normal level. In addition, due to the good robustness of the coordinated control strategy during the fault period, the stable operation of the wind turbine is ensured. The simulation models of VSC-HVDC and DVR for offshore wind farm are built in MATLAB/Simulink, and the simulation verification of three-phase voltage depth sag fault, three-phase short-circuit fault and single-phase short-circuit fault is carried out. The results show that the coordinated control strategy not only improves the efficiency of the system, but also shows good compensation performance in the case of symmetric and asymmetric voltage faults. It has certain practical significance for the reliable operation of offshore wind power system and the improvement of low voltage traversing ability.
【学位授予单位】：燕山大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TM614

【参考文献】