Research on the Dual Modulation of All-Fiber Optic Current Sensor

Abstract

Acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the all-fiber current sensor with a pulsed light source. The pulsed light is realized by amplitude modulation with AOM. The reflected interferometer current sensor is constructed by the mirror and phase modulation with EOM to improve the anti-interference ability. A correlation demodulation algorithm is applied for data processing. The influence of the modulation frequency and duty cycle of AOM on the optical system is determined by modeling and experiment. The duty cycle is the main factor affecting the normalized scale factor of the system. The modulation frequency mainly affects the output amplitude of the correlation demodulation and the system signal-to-noise ratio. The frequency multiplication factor links AOM and EOM, primarily affecting the ratio error. When the frequency multiplication factor is equal to the duty cycle of AOM and it is an integer multiple of 0.1, the ratio error of the system is less than 1.8% and the sensitivity and the resolution of AFOCS are 0.01063 mV/mA and 3 mA, respectively. The measurement range of AFOCS is from 11 mA to 196.62 A, which is excellent enough to meet the practical requirements for microcurrent measurement.

Research on All-Fiber Dual-Modulation Optic Current Sensor Based on Real-Time Temperature Compensation

“…The acousto-optic modulator (AOM) and electro-optical modulator (EOM) are applied to realize the AFOCS based on the reflected interferometer current sensor, which is called dualmodulation AFOCS [23]. The schematic diagram of AFOCS with dual-modulation is shown in Fig.…”

“…The square wave signals can be expanded into the Fourier series, which is the sum of the harmonics of the modulation frequency of AOM. The relevant demodulation method is applied for demodulation to improve the ability of data processing, and the frequency relationship between the AOM and EOM has been described in detail in previous works [23]. The output of relevant demodulation is given by [23]…”

“…The relevant demodulation method is applied for demodulation to improve the ability of data processing, and the frequency relationship between the AOM and EOM has been described in detail in previous works [23]. The output of relevant demodulation is given by [23]…”

Abnormal handling mechanism and improvement measures of optical DC current transformer in smart grid environment

“…Among them, the DC electronic current transformer of Poyang Lake converter station mainly adopts all-fiber optic current transformer has shown abnormal alarm many times in the operation process and led to DC protection false operation. The common all-fiber optic current transformers ( Li et al, 2018 ; Dziuda et al, 2007 ; Wu & Zhang, 2020 ; Li et al, 2019b ) are divided into sine wave modulation (open-loop modulation) and square wave plus step wave modulation (closed-loop modulation) according to their modulation methods ( Wang, Zhang & Pang, 2021 ; Pang et al, 2020 ; Wu, Zhang & Chen, 2022 ). The sine wave modulated full optical fiber current transformer (FOCT) used in Poyang Lake converter station is the mainstream DC electronic type current transformer currently operating in UHV DC converter station, and its reliability is directly related to the safety and reliability of DC transmission system, so its fault mechanism and its abnormality alarm mechanism are also receiving increasing attention ( Temkina, Medvedev & Mayzel, 2020 ; Zhao et al, 2022 ; Qi et al, 2020 ; Bashir Ahmed, 2019 ; Chen, Xu & Wang, 2020 ).…”