数字闭环光纤电流互感器死区形成机理分析

死区是闭环反馈控制系统中常见非线性现象之一,其产生原因是由于增量型非比例反馈通道干扰的存在.在干涉型数字闭环光纤电流互感器系统中,死区将引致系统零偏、零漂等非线性现象.通过系统模型的建立与分析发现,除正常相位补偿机制需要的比例反馈通道外,相位调制信号与光电探测器输出间的交叉电信号耦合、相位调制信号控制误差与相位调制器性能漂移,将在闭环光纤电流互感器中形成了另外一条非比例的干扰反馈通道;干扰通道与干扰信号的相关参数,不仅决定着死区的产生条件,也为抑制死区现象提供有效的解决途径;实验表明,死区现象的非比例反馈通道解释,不仅具有理论上的合理性,而且得到实验结果的支持.

Analysis on the Mechanism of Dead Band Phenomena in Digital Closed-loop Fiber Optic Current Transformers

According to auto-control theoretic, Dead band is one of the popular nonlinearity phenomena in a closed-loop system which arose from the feedback channels with disproportion feedback coefficient. In this paper, nonlinearity errors such as zero bias, zero drifting, resulting from dead band phenomena in digital closed-loop fiber optic current transformers (FOCT), was analyzed by in the application of feedback models. The frequency and phase characteristic of interfering signal and the process that the interfering signal tracked and locked input signal were analyzed to prove that besides the designed phase-compensation feedback channel, electrical crosstalk between phase modulator and photo-electric detector, modulation errors, were the main interference sources, which worked as an abnormal feedback channel and caused dead band phenomena. By the development of dead band model, combining ideal digital model and partial integration model of digital closed-loop FOCT, the condition expression and output errors produced by dead band were derived as well as the means that might be in application to restrain the output errors were discussed.