复杂电磁环境中非线性微弱信号检测的主动噪声控制与信号分离方法

Many superconductors in superconducting electrical equipment operates at either high voltage, high current or strong magnetic fields and other complex electromagnetic environment, and the weak nonlinear resistive component caused by the dynamic changes in the electromagnetic field produces power loss, which is a threaten to the safety of the equipment. Consequently, it is crucial to having a real-time resistance monitoring system. Based on the operating data and experiments of many AC and DC high-temperature superconducting (HTS) cables and coils, this project aims to develop a weak nonlinear signal detection and extraction method in stochastic strong electromagnetic environment. Firstly, the self and mutual induction voltage in measurement circuit caused by non-stationary high voltage, high current or strong magnetic fields is discussed, and the impact of the induced voltage on the detection of random nonlinear resistive voltage on superconductor is investigated. This part aims to solve the problem of electromagnetic compatibility design for different types of HTS power devices. Consequently, an active noise control system for various HTS power devices is exploited, and this part aims to solve the design issues of nonlinear adaptive filter which meets the convergence, robustness and real-time requirements. Further, using the correlation characteristics of the signal-to-noise and signal-to-signal, a signal separation method based on Hilbert-Huang transform and wavelet transform is considered, which aims to solve the problem of low SNR signal extraction in nonlinear, non-Gaussian noise.

超导电工装备中的超导体通常运行在高电压、或大电流、或强磁场等复杂的电磁环境中，其在动态变化电磁场中的微弱非线性电阻性分量将产生有功损耗，可能威胁到装备的安全，必须对该电阻值进行实时的监测。本项目基于大量交直流高温超导电缆、交直流高温超导磁体的运行数据与实验，研究随机强电磁干扰下微弱非线性电压信号检测与信息提取的方法。首先，研究非平稳的高电压、大电流与强磁场如何通过回路自感与互感耦合在测量线路中感应出电压，分析随机的感应电压对超导体非线性电阻性电压检测的影响，解决不同类型超导电力装置的电磁兼容性设计问题；在此基础上，研究如何建立不同类型高温超导电力装置的主动噪声控制系统结构，解决满足系统收敛性、鲁棒性与实时性要求的非线性自适应滤波器设计问题；进一步，利用信号与噪声间的相关性特征，设计基于Hilbert-Huang变换与小波变换的信号分离方法，解决非线性、非高斯噪声中的极低信噪比信号提取问题。

本项目针对超导电缆、超导磁体等装置在复杂电磁环境下的微弱电压信号检测问题开展研究。针对超导装置多金属层复合的结构特征，结合常规微弱信号检测面临的问题，给出了电场耦合和磁场耦合的路径，并针对性提出了抑制和降低电场和磁场干扰的屏蔽和接地措施；针对非线性随机干扰下的噪声抑制，提出了一种鲁棒主动噪声控制系统，解决了高温超导线圈在测试过程中因自感和互感导致失超信号被感应电压信号完全覆盖的难题，并成功应用于高温超导变压器和限流器等装置超导线圈临界电流测试和状态监测中；针对未知统计特性的随机噪声，提出了近邻最小方差的滤波方法，利用固定模态极值间距和幅值检测间歇噪声，结合HHT变换瞬时时频特性实现间歇噪声的定位和分解，实现了在复杂多变的噪声背景下根据信号物理特性实现自适应滤波去噪。