基于中性点IGBT柔性接地的配电网过电压自适应抑制

Single-phase grounding overvoltage, arc grounding overvoltage and three-phase unbalanced overvoltage are the main threats for grid devices and safe operation in power distribution network. Comprehensive studies about the development mechanism and suppression measures of the three kinds of overvoltage have been the leading subject in this field. In this project, the convertion of the neutral grounding mode would be initiated. And the researches on the mechanism that how the three types of overvoltage are influenced by the consistent variation of the neutral grounding electrical parameters would be put forward. Furthermore, the flexible IGBT neutral grounding mode with the consistent variation of the electrical parameters would be set up based on the power IGBT units. Thus the researches on the flexible control strategies and its impact on overvoltage would be carried out. In order to achieve the adaptive control for the three types of overvoltage under different conditions, the flexible overvoltage suppression circuit topology would be established by using modular multi-level technology. And the characteristics of overvoltage identification, triggering control system, and operation control system would be analyzed. The flexible IGBT neutral grounding mode could achieve the adaptive control of the typical overvoltages in power distribution network. Eventually, the real-time monitoring, intelligent identification, and active suppression system would be established by considering the monitoring studies with zero-sequence power capacitive current. The implementation of the project can not only set an example for the suppression of other overvoltage, but also provide an important theoretical basis and technical support for the protection of the power distribution grid equipments and systems.

单相接地、弧光接地以及三相不平衡过电压是威胁配电网设备和系统安全运行的重要原因。系统研究以上配电网过电压的发展机理和抑制措施一直是本领域的前沿课题。本项目拟从改变中性点接地方式入手，研究连续可调的中性点接地电气参数对配电网典型过电压的影响规律；研究通过大功率IGBT元件实现连续可调电气参数的中性点柔性接地方式，建立通过中性点IGBT柔性接地方式抑制配电网典型过电压的控制策略，分析其对过电压的作用机制和影响机理；利用模块化多电平技术，研究中性点IGBT柔性接地方式的拓扑结构和控制开关性能，并分析过电压识别-控制动作-抑制执行的响应特性，实现不同参数条件下的配电网典型过电压的自适应抑制；研究配电网零序电容电流的监测方法，建立配电网过电压的实时监测-智能识别-主动抑制系统并实现挂网运行。本项目的实施可为保障配电网设备和系统的安全运行提供重要的理论支持和技术手段，并可为其他类型过电压抑制提供参考。

本项目的目标是获得基于中性点IGBT柔性抑制的配电网过电压自适应抑制方法。利用双传感单元电压传感器测量过电压信号，采用阈值判断和多级支持向量机结合的方法识别过电压类型，通过改进型线路对地参数测量方法获得较为精确的线路对地参数，同时通过接地故障模拟试验获得故障数据并提取电弧特性，提出了基于IGBT柔性抑制的配电网过电压抑制方法并搭建模型进行了仿真验证，基于现场试验及仿真计算提出了三相无功设备投切过电压的原理与抑制措施。取得的成果如下：.1）基于压电陶瓷和光纤光栅的双传感单元电压传感器监测配电网过电压，获得不受温度影响的过电压信号，进而利用时域分析、频域分析和小波分析等方法提取过电压特征量，得到各类过电压的幅值、陡度和能量分布等特征量，多角度分析并刻画不同过电压信号局部特征及其变化规律，最后结合阈值判断和多级支持向量机构成的模式识别结构进行过电压类型识别。.2）提出了利用激磁阻抗的频率特性提高线路对地参数的测量精度，通过注入信号的向量计算结果对比，发现计及注入变压器激磁阻抗频率特性的计算方法比传统计算方法准确度更高，因此当利用异频电流信号注入的方式来测量线路对地电容时，为了让测量结果更为准确，需预先测取相关频率或者对应频率范围内的激磁阻抗参数。.3）基于10kV试验平台的接地故障模拟试验获得故障电压电流数据，分析并提取了电弧电导及时间常数并搭建了电弧模型，提出了基于IGBT柔性抑制的配电网过电压抑制方法，采用基于实测数据搭建的电弧模型对柔性抑制策略进行了仿真验证。.4）基于现场试验获得三相无功设备投切过电压数据，搭建了断路器的熄弧重燃模型，得到了描述熄弧重燃过程的三个统计参数，基于此进行了相关抑制措施的仿真研究，如避雷器和阻容吸收器的类型、安装位置和安装数量，提出了真空断路器投切10kV并联电抗器过电压的最佳抑制措施，并通过现场试验得到了验证。