配电网单相接地故障柔性自适应消弧方法研究

By breaking through the principle and its limitations of traditional flexible arc-suppression for single-phase grounding fault in non-effective grounding systems, and referring to the technical idea of reactive power compensation and harmonic suppression equipment mounted directly in the medium voltage distribution networks, a novel theory of flexible and adaptive arc-suppression for single-phase grounding fault in distribution networks based on the three-phase cascaded H-bridge converters will be set up. The mechanism of action between the injection current from the single-phase cascaded H-bridge converter and the fault-phase voltage will be revealed. Two novel arc-suppression methods based on separate-phase current and voltage flexible control respectively are put forward. Combining the advantages of two kinds of flexible arc-suppression method, an adaptive arc-suppression method which is capable of bringing the residual current down to zero and adapting to the distribution line parameter and load fluctuation is proposed. The three-phase cascaded H-bridge converters are connected to the distribution networks directly by inductance. During the initial period of single-phase grounding fault, the flexible current arc-suppression method is used for arc-suppression and reliable fault-phase detection. The total grounding current will be compensated by the injection current from any-phase of the converter, which helps to suppress the recovery of fault-phase voltage and avoid the reignition of arc. According to the calculated threshold of zero sequence voltage which reflects the residual value of the grounding fault, whether to switch to a flexible voltage arc-suppression method is determined. So far the flexible adaptive arc-suppression method for grounding fault is implemented. The separate-phase flexible control algorithm and adaptive arc-suppression algorithm are studied too. Taking advantage of the research on the main circuit model and the control systems of cascaded H-bridge converter, the principle prototype will be manufactured. It can be expected to reduce the probability of sustained arc when single-phase grounding fault occurs in the distribution networks and increase the reliability of power supply.

突破传统中性点非有效接地配电网单相接地故障柔性消弧原理及其局限性，借鉴中压配电网直挂式有源无功补偿和谐波抑制装置的思路，建立基于三相级联H桥变流器的配电网接地故障柔性自适应消弧新理论。揭示单相级联H桥变流器注入电流对故障相电压的作用机理，提出基于分相柔性控制的电流消弧和电压消弧新方法，综合两种柔性消弧法的优势，提出一种可适应线路参数及负载变化的配电网零残流自适应消弧方法。三相级联H桥变流器通过电感直接挂接在配电网的相线，在接地故障初始，控制任意相变流器注入电流，补偿流经故障点的接地全电流，抑制故障相电压恢复，并可靠识别出故障相，即采用柔性电流消弧法；根据推算的反映故障残流值的零序电压阈值，确定是否需要切换为柔性电压消弧法，实现接地故障柔性自适应消弧。并研究分相柔性控制及自适应消弧算法，设计级联H桥变流器主电路及其控制系统，完成原理样机研制。有望降低配电网单相接地故障建弧率，提高供电可靠性。

配电网发生单相接地故障时，传统的无源消弧技术无法补偿接地故障电流中大幅提高的有功电流分量和谐波电流分量，系统消弧能力降低，故障点的电弧难以自熄，接地电弧电流的能量及间歇性弧光接地产生的过电压严重威胁系统绝缘，易引起故障扩大，为解决该难题，借鉴中压配电网直挂式有源无功补偿和谐波抑制装置的技术思路，提出一种基于三相级联H桥多电平变流器的配电网柔性消弧装置，并研究与之相适应的单相接地故障柔性自适应消弧方法。分析配电网单相接地故障消弧机理及分相注入电流对故障相电压的作用机理，研究影响电流消弧法及电压消弧法消弧效果的主要因素，分别提出了不需要故障选相但具备故障选相功能的柔性电流消弧新方法，以及以零序电压与故障相电源电压负值相等为控制目标的电压消弧新方法。综合考虑两种柔性消弧新方法的优缺点，提出可适应线路参数及负载变化的配电网柔性自适应零残流消弧理论和方法，利用接地故障后零序电压值的大小作为切换消弧方法的间接条件，在高阻接地故障时采用电压消弧方法，低阻接地故障时采用电流消弧方法，使消弧效果达到最优。研究了三相级联H桥变流器分相注入电流的控制技术，包括以伏秒误差最小为原则的改进型分布式换流调制策略和适用的闭环控制方法，完成了原理样机的研制。搭建了配电网物理仿真实验系统，通过原理样机的仿真及实验测试，验证了理论方法的正确性及可行性。结果表明：该理论技术可解决已有方法存在需接地变及升压变且消弧效果受工况变化影响的问题，降低故障建弧率，提高配电网供电的安全性和可靠性。.已发表相关论文24篇，其中期刊论文19篇，SCI检索10篇，EI检索7篇；出版专著1部；获授权发明专利5项，申请待批准发明专利6项；培养博士在读2人，培养硕士毕业7人、在读4人；指导研究生获中国研究生电子设计竞赛全国一等奖1项，华东分赛区一等奖1项，“互联网+”大学生创新创业大赛省级一等奖1项；研究成果超过项目计划书中的预期目标。