预防风电场不确定性弱馈源脱网保护策略研究

Currently, researches on wind turbines off-grid mainly focus on maladjustment of electronic equipment, change of voltage and reactive power after fault in wind system. However, due to uncertainty and weak-infeed characteristics of wind farm, there is another possibility: large-scale wind turbines off-grid caused by active power fluctuation. The project will focus on this problem and do some related researches..As is known to us, large-scale blackouts are mostly caused by power oscillation in power system, and therefore power imbalance is the root cause of the accidents. In conventional systems, power imbalance is usually caused by a sudden unexpected fault, while wind turbines are unbalanced power sources in wind farm. Although output power of single wind turbine is a trivial in the view of its capacity, large installed capacity and butterfly effect of wind turbines could have a serious impact on the wind farm. As a result, this project will solve the problem from two aspects: First, uncertainty of active power sources is analyzed and the butterfly effect of wind turbines is studied in wind farm, and then relay protection strategy is proposed to avoid large scale blackouts. The main researches are: research on weak-infeed characteristic of uncertain power sources in wind farm; research on change regularity of voltage, current, power, power angle, pitch angle under uncertain factors in wind farm; research on pitch angle adjustment of wind turbines, changes of weather, power fluctuations in wind farm; research on evolution mechanism of wind turbines cluster butterfly effect in wind farm; research on out of step mechanism of uncertain wind turbines cluster and relay protection strategy to avoid large-scale wind turbines off-grid.

目前风电场脱网事故分析主要从电网故障后电子设备不适应、从电压和无功等方面进行。但由于风电场自身存在不确定性和弱馈性特性，还有另外一种大规模脱网事故的可能性：有功波动引起的脱网。本项目针对这一类问题展开研究。.众所周知，电力系统大停电事故大多是功率振荡造成的，功率不平衡是事故的根源。在传统系统中功率不平衡通常是系统故障造成的，而风电场中风机本身就是不平衡的来源。虽从风机单机容量来看，这种不平衡微不足道，但风电场总容量巨大和风机的蝴蝶效应将会引起大规模脱网。本项目首先分析风电场有功不确定源和蝴蝶效应现象，其次提出继电保护防范策略。主要研究有：风电场不确定源、弱馈性特征研究；风电场电压、电流、功率、功角、风机桨距角等在不确定因素下规律性研究；风电场风机桨距调节惰性，天气因素变化，功率波动分布状况研究；风电场机组群蝴蝶效应演化机理研究；不确定性风机群失步机理与防止大规模脱网预防保护策略研究。

现有针对风电场脱网事故分析主要从电压和无功等层面展开，事故诱因多被归咎于故障后电力电子设备的不适应，忽略了风电场自身不确定性和弱馈特性从有功层面引发风机大规模脱网的可能性。本项目针对风电场自身的不确定性、弱馈特性的特点，深入研究了风电场弱馈源机端电压、馈出电流、谐波、等效阻抗及电势等典型电气量在不确定因素条件下变化规律，分析了不确定性扰动条件下风电场弱馈源的相互作用机理与集群效应，并在此基础上以确保风电场的功率平衡为目标，提出了基于风机脱网风险在线评估的集电线路保护方案、基于熔断器动作特性的风电场反时限协调保护方案、基于多重分形谱的风电场故障方向判别协调方法、计及风电场不确定弱馈特性的广义阻抗选相新原理、计及风电弱馈源频率特性的综合优选制幅值差动保护方案、基于多代理模式的风电场区域化协同保护策略。本项目提出的保护策略充分考虑了风电场不确定性下的单机弱馈特性与机群特性，通过从预防保护、自适应保护以及协调保护等方面进行综合处理，可有效降低风机非计划脱网的可能性，为应对国内外频发的风电场连锁脱网事故提供了很好的解决思路。依托该项目发表了期刊论文8篇，国内外会议论文18篇，共17篇被SCI、EI收录；培养了3名博士研究生以及10名硕士研究生。