风电汇集地区电压不平衡特性分析及抑制策略

中国风电多采用"大规模集中开发,远距离传输"的模式,风电汇集地区常无本地负荷,在大规模风电汇集地区常出现三相电压不平衡现象,严重时会造成风机脱网,威胁到电力系统的安全稳定运行.针对这一问题,提出了风电汇集地区电压不平衡机理及抑制策略.首先,基于实测数据提取风电汇集地区电压不平衡现象的关键技术特征;其次,构建风电汇集地区等效电路模型,考虑风电汇集地区静态电压稳定极限及不换位输电线路三相阻抗参数不平衡等因素,提出电压不平衡度的估算方法;最后,以汇集站负序电压最小为目标,提出风电汇集地区三相无功优化模型,通过动态无功补偿装置分相调节实现风电汇集地区负序电压抑制.以实际风电汇集系统为例,通过仿真分析验证了机理分析和抑制策略的有效性.

Characteristics Analysis and Suppression Strategy of Voltage Unbalance in Areas with Integration of Wind Power

The wind power in China mostly adopts the mode of concentrated development in large-scale and long-distance transmission and there are often no local loads in the wind power integrated areas. Therefore, three-phase voltage unbalance frequently occurs in the areas with large-scale integration of wind power, which can cause wind turbines to disconnect from the grid in severe cases, threatening the safe and stable operation of the power system. In response to this problem, the voltage unbalance mechanism and suppression strategy in the areas with integration of wind power are proposed. Firstly, key features of voltage unbalance phenomenon in the areas with integration of wind power are extracted based on the actual data. Secondly, the equivalent circuit model is constructed in the areas with integration of wind power. Considering the static voltage stability limit and unbalanced three-phase impedance of untransposed transmission line, a method for estimating the voltage unbalance factor (VUF) is proposed. Finally, with the objective of minimizing the negative sequence voltage of the integrated substation, a three-phase reactive power optimization model for the areas with integration of wind power is proposed, and the negative-sequence voltage suppression in the areas with integration of wind power is achieved through adjustment of the dynamic reactive power compensation device to each phase. Taking the actual wind power integration system as an example, simulation analysis verifies the effectiveness of the mechanism analysis and suppression strategies.