基于基频混频的相位生成载波解调方法研究与改进

In this paper, total harmonic distortion (THD) of phase generated carrier demodulation algorithm by digital arctangent approach (PGC-DAT algorithm) is analyzed. THD due to the deviations of modulation depth and carrier phase delay is investigated both theoretically and experimentally. The analytical expression of THD as the function of carrier modulation depth, signal amplitude, initial phase and deviations of modulation depth and carrier phase delay has been derived. According to our analysis, the maximum THD for different initial phases exists, which reaches the peak value when the signal amplitude is close to 1.2 rad. The best modulation depth to minimize the maximum THD is 2 rad. Finally, an experimental system is set up with the mean THD below -60 dB. The analytical expression of THD derived in this paper agrees well with the experimental results.

We present an optical fiber voltage sensor by Michelson interferometer (MI) employing a Fabry–Perot (F–P) tunable optical filter and the phase generated carrier demodulation algorithm. By mounting an MI fabricated by an optical fiber coupler on a piezoelectric transducer, a dynamic strain would be generated to change the phase difference of the interferometer when the measured voltage is applied on the piezoelectric. The phase generated carrier demodulation method was used to obtain the phase variation of the interferometer by applying demodulate signal on an F–P tunable optical filter. The measured voltage can be obtained by the variation of the phase; the random phase shift in the interferometer and the intensity fluctuation of the light source of the sensor can be eliminated. The experiment results show that the relation between the phase variation and the voltage applied on the piezoelectric is approximately linear. The dielectric reliability of the sensor has been verified according to the IEC standard.

In this paper we propose a novel, improved, phase generated carrier (PGC) demodulation algorithm based on the PGC-differential-cross-multiplying approach (PGC-DCM). The influence of phase modulation amplitude variation and light intensity disturbance (LID) on traditional PGC demodulation algorithms is analyzed theoretically and experimentally. An experimental system for remote no-contact microvibration measurement is set up to confirm the stability of the improved PGC algorithm with LID. In the experiment, when the LID with a frequency of 50 Hz and the depth of 0.3 is applied, the signal-to-noise and distortion ratio (SINAD) of the improved PGC algorithm is 19 dB, higher than the SINAD of the PGC-DCM algorithm, which is 8.7 dB.

The phase generated carrier (PGC) demodulation technique for phase-sensitive optical time-domain reflectometry (Ф-OTDR) has significant potential in applications involving distributed optical fiber sensing and imaging. An improved PGC demodulation algorithm for a Ф-OTDR combined with an unbalanced Michelson interferometer system is presented in this letter. This modified PGC technique uses the one output signal as a fundamental carrier frequency signal with mathematical transformations, and another output is the modulated signal, which enable the two signals to be output synchronously from the interferometer. Theoretical simulations and experiments demonstrate that the linear and nonlinear distortion caused by phase modulation depth and carrier phase delay are well suppressed by the proposed algorithm with high stability and low distortion. The signal-to-noise-and-distortion ratio of sensors using the proposed method in the same conditions achieve gains of 12.98 dB, 30.82 dB and 6.93 dB over PGC-Arctan, PGC-differential-and-cross-multiplying and PGC-single-path differential division method, respectively. Experimental verification shows that the proposed demodulation system can exactly recover the original signals of multiple vibration positions simultaneously, and the system employing the ameliorated PGC demodulation algorithm has the noise level of about 1.83 × 10−4 rad (√Hz)−1 and a large dynamic range of 65.72 dB @ 800 Hz, which provides a new choice for distributed optical fiber sensing technology.

A low-finesse all-fiber sinusoidal phase modulation interferometer for displacement measurement

一种消除伴生调幅影响的PGC解调方法

In this paper, we demonstrate an improved dynamic demodulation system for acoustic sensors based on distributed feedback-fiber laser (DFB-FL). The signal is demodulated using the phase-generated carrier (PGC) demodulation technology based on unbalanced Michelson interferometer (MI). An improved PGC demodulation algorithm is introduced, which solves the problems of light intensity disturbance (LID) and phase modulation depth drift in the traditional PGC demodulation algorithm that affect the demodulation results. The acoustic pressure sensitivity test of a packaged DFB-FL acoustic sensor is carried out to evaluate the performances of the demodulation system, a flat acoustic pressure sensitivity and frequency response curve was achieved in the frequency range of 200 Hz~18 kHz, the wavelength-acoustic sensitivity was about -40.22 dB re. pm/Pa. The amplitude changes of demodulation signal with light intensity and modulation depth are also tested, and it shows that the stability of the demodulation system has been significantly improved.

In this paper, we propose a distributed vibration fiber sensing system based on Polarization Diversity Receiver(PDR). We use Acoustic Optical Modulator(AOM) to generate pulse light and an unbalanced M-Z interferometer to generate two pulse light with a certain time delay in the same period. As the pulse lights propagating in fibers, the Backward Rayleigh scattering lights will interfere with each other. The vibration on the fiber will change the length and refractive index of fiber which results in the change of the phase of the interference signal. Hence, one arm of the M-Z interferometer is modulated by a sinusoidal phase-generated carrier(PGC) signal, and PGC demodulation algorithm has been used to acquire phase information from the Backward Rayleigh scattering lights. In order to overcome the influence of polarization-induced fading and enhance Signal Noise Ratio(SNR), we set a PDR before the photo detector. The Polarization Diversity Receiver segregates the interfere light into two lights with orthogonal states of polarization. Hence, there is always one channel has a better interfere light signal. The experiments are presented to verify the effectiveness of the distributed vibration fiber sensing system proposed.

The monitoring and modelling of the Li-Ion Batteries behaviour is still a major technical challenge due to the non-linearities and coupled phenomena that determine their operation. These Li-Ion Batteries can consist of thousands of cells with series/parallel connections, which suffer from operating and degradation deviations. The pursuit of new, increasingly intelligent and heavier state estimation algorithms requires a significant amount of data and computational power, which can be challenging to deploy in current Battery Management System solutions. To solve this problem, this paper proposes a Digital Twin Simulation Platform that considers all the individual cells based on the Cloud to extend the computational power and data storage capacity. This work presents validated cell models, a module-level modelling approach, and an experimental validation platform is suggested. In addition, the first results obtained when implementing the Digital Twin Simulation Platform in the Cloud are presented.

The reactive power compensation device plays an important role in improving the power quality and safety and stability of the power system. Three-phase H-bridge STATCOM topology has become a major structure in low-voltage system. The double-ring top-level control strategy based on PI and feedforward decoupling and the PSCAD and C interface technology are raised in this paper. On the one hand, the system main circuit is built by PSCAD / EMTDC software using its own power system and power electronic components. On the other hand, the program of instantaneous reactive power and SPWM modulation strategy based on C language is compiled, and PSCAD / EMTDC and C language interface is achieved. On the digital simulation platform, the instantaneous reactive power algorithm of three-phase H-bridge STATCOM and the contrast analysis of different SPWM modulation strategies are completed. The simulation results verify the feasibility of the digital simulation technology.

Modelling, simulation and experimental verification for renewable agents connected to a distorted utility grid using a Real-Time Digital Simulation Platform

In order to accurately analyze Jilin power grid with UHVDC, this paper builds the electromagnetic transient model of Jilin HVDC system and the electromechanical model of the rest of Jilin power grid based on the winter heavy load of Jilin power grid in 2018 with full digital real-time simulation platform power system. Based on the electromechanical- electromagnetic hybrid model built up, the steady state simulation of Jilin HVDC is carried out. The transient simulation results of electromechanical transient model and electromechanical-electromagnetic hybrid model are compared in the case of bipolar blocking. The simulation results show that the electromechanical electromagnetic hybrid model can effectively reflect the electromagnetic transient characteristics of the UHVDC transmission system in Jilin, and is suitable for studying the very complex and fast transient process in the DC system. The hybrid simulation model lays a foundation for the study of the impact of Jilin UHVDC.

The requirement of building the simulation platform of digital engine is presented, and the framework pattern is put forward at the beginning. Then the goal and the detailed building route of the simulation platform are designed following the overall framework. In the end, the role of each system in the platform and their correlativity is illustrated. The result of this study would be provided for the automatic analysis of the engine simulation and the further application of the simulation platform.

It is of great significance to study the deep integration of manufacturing technology and new-generation information communication technology under vibration interference of machine tools to improve the intelligence level of CNC machine tools. In this paper, a numerical control manufacturing workshop affected by vibration in discrete manufacturing is taken as the research background, and a solution for a digital workshop operation simulation platform based on the industrial internet is proposed. By constructing the simulation environment of the operation process of the digital factory, the generation and transmission of manufacturing information in the digital factory are simulated. The application architecture of the machining workshop based on a numerical control simulation platform is proposed, and the business process of the numerical control machining workshop is analyzed. Then, the key technologies of NC machine tool modeling, synchronous mapping of data and model, data integration, and fusion are studied. Through the integration and implementation of the NC machine tool simulation platform in the machining workshop, the top-down data instructions can be issued accurately, and the bottom-up feedback information can be confirmed in time. Finally, the system is applied to the electronic information and ship machining workshop to verify the effectiveness of the system framework and method proposed in this paper.

Research and Implementation of Digital Twin Modeling and Simulation Platform