新一代电力系统中谐波发射水平评估理论与方法研究

High permeability of renewable energy and high proportion of power electronic equipment in power network results in serious harmonic pollution and the pollution brings a challenge to the safety and stability of power grid. The harmonic emission at a point of common coupling (PCC) is the result of combined action for utility side and customer side. The premise of harmonic control is that the emission level and the responsibility of both sides can be evaluated correctly. However, the existing evaluation methods have produced wrong results because their assumptions can’t satisfy the features of the current power system. Thus, it is necessary to study new theories and methods of harmonic emission level evaluation for new generation power system. . In this project, by using the superposition principle, signal decomposition and fractal theory, the basic properties of the solution of harmonic equivalent circuit equation at a PCC of power system are studied. The general solution expression and the complete solution spatial characteristic analysis are given, which provides theoretical support for the new technology. On this basis, the reasons why the existing evaluation technology based on those assumptions fail and the evaluation technology which suitable for new generation power system is put forward. It mainly includes the solution method when the harmonic impedances of both sides are approximately equal and the fluctuations of the harmonic sources of both sides are almost equal. In order to improve the accuracy of harmonic evaluation based on blind source separation, the fast variable component extraction technology of measurement data is studied. The fractal characteristics between measured data and harmonic sources are discussed, and an evaluation technique based on fractal exponent using measured data is proposed. Besides the technologies above, the performance of supposed method is studied.. The research results of this project will provide a theoretical basis and technical means for the evaluation of harmonic emission level for the new generation of power systems.

高渗透率可再生能源、高比例电力电子装备广泛接入电网，致使电网的谐波污染严重，影响电网安全稳定运行。谐波治理的前提是谐波发射水平及责任的准确评估，但现行的评估方法因其假设条件不再契合电力电子化的电网特性，会产生错误结果。因此有必要研究新的理论与方法，提出适合新一代电力系统的谐波发射水平评估技术。拟采用叠加原理、信号分解和分形理论，研究公共联结点谐波等效电路方程解的基本性质、通解表达式及解空间特性分析。同时分析现有评估技术假设条件失效原因，提出有效的评估技术，主要包括公共联结点两侧谐波阻抗值相近时和两侧谐波源波动相当时的求解方法；研究量测数据快变分量提取技术，提高基于盲源分离技术的评估精度；研究量测数据与谐波源的分形特征关系，提出利用量测数据分形指标的评估技术，同时给出所提方法的性能边界及结果的验证方法。本项目研究成果将为新一代电力系统的谐波发射水平评估提供理论依据与技术手段。

高渗透率可再生能源、高比例电力电子装备分散式多点入网，电网谐波发射呈现高频次、宽频域、广分布特性，项目围绕谐波发射评估不同工况场景开展细致深入研究：1）关注到用户侧加装滤波器导致两侧谐波阻抗非远大于关系及两侧谐波源非统计独立特性，提出基于谐波量测数据不同时间间隔弱相关特性等系列系统谐波阻抗估计新技术，开拓了仅依据测量数据而无需任何假设的谐波阻抗估计新路径；2）针对传统有功功率方向法溯源结果不可靠问题，提出基于阻抗约束新功率法的谐波快捷溯源定位新技术；3）针对运行方式改变导致系统阻抗改变问题，提出基于最小加权变分约束的时变阻抗追踪技术；4）提出一种无须求解谐波转移阻抗的多谐波源责任量化方法，实现强背景谐波波动时多谐波源电流解耦与谐波责任准确量化；5）针对监测装置不足、谐波状态不可观时谐波溯源定位难以实现的问题，提出基于改进遗传算法与最小范数约束的多谐波源定位方法，在有限的谐波源先验信息下实现可靠的多谐波源定位与发射估计；6）针对长线路/电缆谐波传导及放大特性，提出了谐波放大与电缆长度、谐波频次等参数相关量间的定量关系；7）针对计及线路分布参数后，谐波不稳定分析面临系统超越方程零极点难以求解的问题，提出一种基于Pade近似的超越方程零极点求解方法，可在宽频域下准确评估系统稳定性与谐波放大点；8）针对现有电压暂降严重性评估方法中历史监测数据及多源数据利用不充分问题，提出基于数据挖掘的电压暂降影响严重程度评估方法，提升电压暂降严重性评估的准确性。发表SCI/EI论文27篇，授权发明专利12项，参与制定行业标准1项，以第一完成人获得四川省科技进步奖三等奖1项，筹办谐波发射特性评估行业论坛1次，参与国内外相关会议并多次做主题发言，培养博士研究生3人，青年教师1人。项目保质保量并超额完成预期目标，研究成果对日益恶化的电能质量及谐波污染管控，具有重要的理论和工程价值。