交直流混杂环境下基于关键参数辨识的变压器直流偏磁保护策略研究

The DC-biased transformer have affacted safety and stability of power system in the AC-DC hybrid environments such as high-voltage direct-current transmission and the magnetic storm in power network. As the nonlinear exciting characteristic is susceptible to the DC disturbance, the traditional protections operate with risk and can not solve the abnormal matters in transformer such as vibration, overheat and so on. In this project, the problems above will be researched with the application of inductance in novel principle of protection. The field-circuit coupled method for DC-biased transformer is built from the point of energy transforming. The time-domain current and dynamic inductance are used as key parameters in the characterization of saturated excitation of transformer. The variation of the key parameters, excitation and harmonics is analyzed with DC disturbance. And the inherent relations between exciting saturation and key parameters with DC-biasing disturbance will be explored. On this basis of key research on parameter identification, the quantitative evalutation index of DC-biasing effect is determined. Thus the abnormal matters in transformer can be associated with the key parameters. The protect criterion can be put forward based on the parameter identification, and the assessment and protection for DC-biased transformer will be realized. The main research achievements will have important scientific value and practical meanning to improve the DC immunity of electromagnetic devices as transformer and power system, which takes significant feature and innovation in the protection for DC-biased transformer.

高压直流输电和磁暴灾害等条件下直流扰动通过接地中性点注入交流电网，导致了交直流混杂环境下的变压器直流偏磁问题。变压器直流偏磁时电流、电感等参数发生畸变，使依赖于这些参数的保护出现误动和拒动问题，从而对设备乃至电网的安全稳定运行造成巨大危害。本项目针对变压器直流偏磁引起的保护问题，拟结合基于电感参数的变压器保护方法，在思想上突破传统以电路或磁路计算为基础的变压器保护，基于能量扰动原理建立计及直流偏磁的场路耦合模型，利用电感等关键参数表征变压器直流偏磁电磁特性，构建偏磁效应量化评价指标将故障特征与关键参数关联，通过理论分析、数值仿真与实验模拟相结合的方法，从电磁耦合角度深入分析变压器偏磁效应的物理本质，开展基于参数辨识的变压器直流偏磁效应评估与保护策略研究。项目研究能够提高变压器等电磁设备及交流电网抗直流扰动的安全稳定性，将在变压器直流偏磁保护方面形成鲜明特色与创新。

电力变压器是电力系统的关键元件，其运行状态直接影响到电力工业的健康稳定性乃至社会的公共安全性。高压直流输电和磁暴灾害等条件下直流扰动通过接地中性点注入交流电网，导致了交直流混杂环境下的变压器直流偏磁问题，进而出现励磁饱和、电流畸变、谐波剧增等异常，并伴随局部放电、温升振动及噪声等一系列不良反应，同时引起保护装置误动或拒动等问题，从而导致电网瘫痪或停电。本项目针对变压器直流偏磁引起的保护问题，结合基于电感参数的变压器保护方法，在思想上突破传统以电路或磁路计算为基础的变压器保护，基于能量扰动原理建立计及直流偏磁的场路耦合模型，提出励磁电流、动态电感等关键电磁参数与变压器励磁状态的合理映射方法，实现基于电磁耦合机理的变压器关键参数辨识技术；研究变压器内部故障并提取谐波、温升及振动噪声等异常特征信息，提出利用关键参数表征偏磁异常特征的方法，构建相应的量化评价指标，实现变压器运行状态量化评估技术；利用量化评价指标进行变压器运行安全分析与评估，开展基于参数辨识的变压器直流偏磁效应评估与保护策略研究。在此基础上解决 “三高一同步”的技术瓶颈，研发了具有电能质量分析、电磁参数辨识和运行状态评估功能的电力变压器运行状态智能监测系统。本项目成果促进了变压器直流偏磁状态监测领域的技术进步，能够提高变压器等电磁设备及交流电网抗直流扰动的安全稳定性，在电力系统稳定与设备偏磁保护方面具有重要意义和深远的产业化前景。