Synchronous Detection Method Research Articles

Low-frequency vibration measurements in harsh environments using a frequency-modulated interferometer

Low-frequency vibration measurements in harsh environments are considerably challenging owing to strong background noise. In this study, a simple, high-dynamic-range, and high-precision vibration-measuring system using a frequency-modulated interferometer was proposed and validated. Harmonics with perfectly orthogonal phases were extracted directly from the interference signal, and noise with random frequencies was filtered using a synchronous detection method. The modulation index of the interferometer was controlled to remove the effect of Bessel functions; hence, a full-circle Lissajous diagram was obtained. The ratio of the two harmonics was used to determine the vibration; hence, the effects of intensity fluctuation and background noise can be neglected. The vibration measurement bandwidth was well controlled by controlling the modulation and cutoff frequencies of the bandpass filters. The best noise level of 1 nm/√Hz under harsh measuring conditions can be archived in the low-frequency range.

Spatially synchronous fringe detection: a method to facilitate the alignment of an echelle grating mosaic by separating the compensative angular errors

Alignment of mosaic gratings is traditionally supported by two interferometric verifications: on the zero order to verify the grating surfaces and on the blaze to verify the groove direction. In the case of low frequency echelle grating an interferometric measurement on the zero order is hardly feasible due to extremely low contrast of the fringes. The complete alignment has then to be carried out on high order (close to the blaze) where the two misalignment errors (the tip and rotation) show the same effect on the interferogram. The acquisition of a low and a high diffraction order image simultaneously, referred to as the spatially synchronous fringe detection method (SSFD), is used to analyze the misalignment. Iterative adjustment with the autocollimation configuration at the low and high order is used to separate the compensative errors of Δθ x and Δθ z . A prototype mosaic with two 110mm×220mm segments has been aligned with the support of this method. A numerical simulation of the alignment procedure as well as the error orientation analysis of this mosaic grating are presented. The mosaic grating with an accuracy of Δθ x <0.64µrad, Δθ y <1.13µrad, Δθ z <0.65µrad and a wavefront RMS error of 0.149λ has been completed. This method can greatly facilitate the alignment of an echelle mosaic for an astronomical spectrograph.

NOUVEAU FILTRE DE PUISSANCE ACTIVE SHUNT BASÉ SUR UN ONDULEUR NPC À NEUF NIVEAUX UTILISANT LA STRATÉGIE DE MODULATION MC-LSPWM

This paper presents a novel shunt active power filter (Shunt APF) system based on a nine-level neutral point clamped (NPC) inverter, which can reduce current harmonics under various nonlinear loads. These loads can introduce harmonic currents within the system, which causes excessive power losses and alters the voltage systems' characteristics. Today, multi-level inverters are more suitable for high-voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. The reference signals required to compensate harmonic currents use the synchronous detection method (SDM) with phase disposition sinusoidal pulse width modulation (PD-SPWM) control due to its low complexity and superior performance. The proposed shunt APF configuration simulation is evaluated using MATLAB-Simulink and SimPowerSystem environment with inductive and capacitive non-linear loads. The simulation results show the efficiency of the proposed shunt APF in terms of harmonic compensation and power quality improvement. The results of comparative studies with other less multi-level inverters confirm the superiority of the proposed shunt APF system.

Control Scheme Influence on the Performance of Shunt Active Power Filter based on Five-level NPC Inverter in Steady and Transient Conditions

This paper presents an investigation on the performance of shunt active power filter (Shunt APF) systems based on five-level neural point clamped (NPC) inverter in steady and transient conditions adopting a fuzzy control scheme. The shunt APF is operated as a current source connected in parallel with the non-linear loads to inject compensates current harmonics into the AC source. The multi-level inverters have gained considerable interests in last year’s. Five-level inverter is recommended in medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, low voltage stress of power semiconductors and low acoustic noise. Secondly fuzzy logic has been widely used in various industrial applications. To benefit from these advantages a shunt active power filter based on five-level (NPC) inverter using fuzzy control scheme is presented in this work. To identify the reference currents, synchronous detection method (SMD) is adopted. Proportional integral voltage controller is used to maintain the dc voltage across capacitor constant and reduce inverter losses. The simulation is performed using MATLAB-Simulink software and SIMPOWERSYSTEM toolbox. The obtained results in steady and transient states illustrate the performances and the effectiveness of the proposed shunt APF system.

Impact of Converter Topology on the Shunt Active Power Filter Systems Efficiency

This paper presents the performance of shunt active power filters (Shunt APFs) which can compensate harmonic currents generated by no-linear load based on five and seven-level neural point clamped (NPC) inverters. Multilevel inverters are currently being investigated and used in several industrial applications. Their advantages include the capability to reduce the harmonic content and decrease the voltage or current ratings of the semiconductors. On the other side, fuzzy techniques are successfully employed in various industrial applications; they represent a good alternative to traditional control systems. To benefit of all these advantages an efficient control scheme for five and seven-level Shunt APF based on multi-carrier pulse width modulation (MC-PWM) and fuzzy control approaches are adopted in this work. The fuzzy controller is designed to improve compensation capability of shunt APF by adjusting the error using a fuzzy rule. The control strategy to identify the current reference uses synchronous detection method (SMD), this technique is easy to implement and achieves good performances. The numerical simulation results carried with MATLAB-Simulink and SimPowerSystems Toolbox show the effectiveness of the proposed systems and confirm the superiority of the seven-level shunt APF compared to five-level configuration system.

Algorithm for identifying RLC parameters

The article discusses an algorithm capable of determining the substitution scheme of the investigated circuit and calculating the parameters of its elements without operator intervention, based on the admittance frequency characteristics. This algorithm enhances the functional capabilities of RLC meters and can be applied to solve practical problems related to identifying the substitution scheme of the investigated circuit. As an RLC meter measures the total resistance only at one or several fixed frequencies, obtaining an understanding of the substitution scheme from these measurements is challenging. To select the substitution scheme, an analysis of the impedance or admittance frequency characteristics is required. Typically, this analysis is performed manually and is time- consuming. The proposed algorithm automates the analysis of the admittance frequency characteristics. The algorithm associates values and the sequence of slopes of the admittance frequency characteristics with an array of known sequences and slope values for known substitution schemes. The calculation of substitution scheme parameters is based on the resonance frequencies and the heights of zero slopes. To minimize the impact of noise on result accuracy, a synchronous signal detection method is employed. The article introduces a criterion for assessing the algorithm's performance and conducts testing on several types of circuits. During testing, the relative error in calculating substitution scheme parameters was evaluated, with a maximum value not exceeding 6 %.

A Synchronous and Accurate Detection Method for Gas Pipeline Leakage Position and Flow Rate Based on Double Fiber Bragg Gratings

Fast and accurate detection of pipeline leaks plays an important role in reducing economic losses and ensuring the safety of personnel. However, for the two important indicators of gas pipeline detection, how to effectively detect the leakage location and leakage rate simultaneously is a serious challenge. In this paper, we present an innovative optical fiber detection method based on double fiber Bragg gratings (FBGs) string to solve this problem. Combined with the theory of material mechanics and fluid mechanics, the binary equations are derived as the demodulation formula. In the detection, the corresponding physical quantities can be calculated by substituting the center wavelength of the two FBGs after drift. The experiments demonstrate that this sensor’s gas flow rate sensitivity in different positions can be up to 466.67 pm∙s/m. Meanwhile, at the same flow rate and different leakage positions, the sensor has sensitive symmetrical performance. The error results manifest that the velocity error is not more than 0.13 m/s, and the relative position detection error is not more than 0.167%. Overall, besides the extended measurement range and excellent linearity, our method also has the advantages of low production cost, simple structure and ease of production, which is more suitable for gas pipeline health monitoring in the future.

Simple Control Method for Unified Power Quality based on Five-level Inverter Topologies Operating under all Voltage Disturbances

This paper proposes a simple control scheme for UPQC (Unified Power Quality Conditioner) system based on five-level NPC (Neutral Point Clamped) inverter capable to compensate all disturbances under all voltage conditions. The proposed UPQC is designed by the integration of shunt and series APFs (Active Power Filters) sharing a common dc bus capacitor. The dc voltage is maintained constant using proportional integral voltage controller. To get the reference signals for shunt and series APFs, synchronous current detection method (SCD) and instantaneous reactive power (PQ) strategies are adopted. These reference signals are derived from the control algorithm and injected in LS-SPWM (Level Shifted-Sin Pulse Width Modulation) controllers to generate the switching signals. The performance of proposed UPQC system is evaluated using MATLAB-Simulink software and SimPowerSystem Toolbox for all voltage disturbances compensation. The simulation results demonstrate the effectiveness of proposed UPQC system to improve the power quality at the common connection point of the non-linear load in steady and transient conditions operation.

Synchronous three-dimensional detection method for multiple parameters of wind fields based on vector principle.

In the area of air-assisted spray, conventional detection of speed and direction of the wind fields for spray are separately conducted, and multiple kinds of sensors have to be laid on each coordinate axis during multidimensional detection. It limits the optimization of operation effect of sprayers based on wind-field distribution characteristics. This paper proposes a novel detection method to achieve synchronous measurement of wind speed and direction in three dimensions. Wind flow was considered as vectors and the sensing structure with a regular triangular pyramid shape supported by cantilever pieces was established. Strain gauges were utilized to detect the deformation in each direction by the wind thrust onto a ball before and after wind flow. Moreover, the calculation models of wind speed and direction were developed respectively based on the relationship of 'strains-force-wind pressure-wind velocity' and the principle of space operation of vectors, so multiple parameters of wind fields could be obtained simultaneously. Calibration was conducted based on a wind tunnel and the Testo 405i anemometers. The results showed that: the minimum relative error of wind-speed values was about 0.06%, while the maximum was about 10%. The average relative error of all the directions was less than 5%. Furthermore, the measurement of the wind among artificial tree canopies demonstrated that the proposed method could effectively measure both speed value and direction of the wind among canopies, and it also helped to find the wind distribution characteristics of the fan, SFG4-2R. The results highlighted both the reliability and the practical meaning of the proposed method, which could be a technical solution for measuring and evaluating wind-field characteristics of sprayers.

Analysis of predictive control algorithm based PWM boost converter-based hybrid networks

The Power Electronic Converter (PEC) interfacing with the Renewable Energy Hybrid System (REHS) like solar, wind, etc is very much important and its implementations and validations are most required to reduce the harmonic distortions, unity power factor, DC-link voltage regulation, and lower frequency with high-speed operations. The PEC is like us three phase Pulse Width Modulation of Bidirectional Power Electronic Converter (BPEC). This paper proposes the novel Tracking Controller based Predictive (TCP) with PI controller is implemented and validated using dSpace TMS 1102 Digital Signal Processor in the VSC. This processor is used to generate the reference currents and a novel tracking controller based predictive Instantaneous Reference Current Generation using Synchronous Detection Method (IRCGSDM), based on this controller the real time data are sensed through current and voltage transducer from 1KVA inverter realized and software (MATLAB Simulink) simulations are validated through MATLAB Software, This novel TCP controller algorithm achieved a fast response in the DC-link voltage regulation, reactive power compensation with unity power factor and nearest sinusoidal grid currents using predetermination of cost function minimization.

The Current Synchronous Detection Method Combined with Positive Sequence Detector for Active Power Filters

The Current Synchronous Detection Method Combined with Positive Sequence Detector for Active Power Filters

Shunt Active Power Filter Performances based on Seven-level NPC Inverter using Fuzzy and LS-PWM Control Scheme

This paper presents novel seven-level neutral point clamped (npc) shunt active power filter system based on LS-PWM and fuzzy control approaches which can eliminate current harmonics generated by nonlinear loads. Today, multi-level inverters are strongly used in the medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. Second, fuzzy logic techniques have been successfully employed in several power electronic applications. Fuzzy controller does not need an accurate mathematical model, can work with imprecise inputs, can handle non-linearity, and are more robust than conventional controllers. To benefit from these advantages a novel control scheme for seven-level (npc) inverter based on Fuzzy and LS-PWM technique is proposed. The reference current signals required to compensate harmonic currents use the synchronous current detection method, this technique is easy to implement and achieves good performances for harmonic compensation. The proposed shunt APF is evaluated using Matlab-Simulink software and SimPowerSystem Toolbox under transient and steady state for various operation conditions. The simulation results show the effectiveness of the proposed shunt active filter based on seven-level (NPC) inverter for improving the power quality and the superiority of combined fuzzy and LS-PWM control scheme to conventional controller in term of harmonics compensation and dynamic performances.

Permanent magnet synchronous generator short circuit detection and circuit shutoff method

Permanent magnet synchronous generator short circuit detection and circuit shutoff method

A Synchronous and Accurate Detection Method for Gas Pipeline Leakage Position and Flow Rate Based on Double Fiber Bragg Gratings

A Synchronous and Accurate Detection Method for Gas Pipeline Leakage Position and Flow Rate Based on Double Fiber Bragg Gratings

Distributed synchronous detection for false data injection attack in cyber-physical microgrids

The distributed cooperative control of microgrids depends on immediate communication and accurate operation information to enhance stability and reliability. The cyber security in cyber-physical microgrids has drawn more attention in smart grids. Among lots of cyber attacks, false data injection attack (FDIA) that replaces the measurement and transmission data with the state variables containing the attack signal, is the prominent attack in microgrids. This paper analyzes the impact of FDIA on the distributed control and concentrates on the distributed detection approach to recognize FDIA locally. Firstly, the attack forms of FDIA are discussed and the two-stage model of FDIA is constructed to represents the two results in microgrids. Then, the distributed synchronous detection method that only requires the neighboring communication is proposed to recognize whether the FDIA occurs in local. Moreover, the feedback function based on the dynamic time wrapping distance is designed to adapt to delayed communication and different attack signals. The simulation results explain the effectiveness and practicability of the proposed model and method.

Unbalance Vibration Control for MSCMG Based on High-Precision Synchronous Signal Detection Method

The active magnetic bearing rotor in magnetically suspended control moment gyro (MSCMG) will produce unbalance vibration due to the mass unbalance, and the frequency equal to the rotation speed. In order to suppress the unbalance vibration of MSCMG, the working principle of the active magnetic bearing (AMB) is introduced and the unbalance vibration model is established. And then, a high-precision closed-loop detection method of the synchronous signal based on synchronous rotating frame transformation (SRFT) is proposed. This method can detected synchronous signals in two directions at the same time, with less calculations. The synchronous current is suppressed by detecting and compensating the synchronous component in the output signal of the displacement sensor, which can reduce most of unbalance vibration. The phase modulation angle is introduced to make the algorithm have a wider stable range. In order to simplify the analysis method, the orthogonal characteristic of the output signal of the displacement sensor is used to equalize the dual output system to a complex-coefficients single-input system, and the dual frequency Bode diagram is used to analyze and evaluate the stability of the system. Finally, experimental results are given to verify that this method can effectively suppress synchronous current.

Harmonic Mitigation in Electric Railway Systems Using Improved Model Predictive Control

An electric multiple unit (EMU) high-speed train is the dynamic load that degrades the power quality in an electric railway system. Therefore, a power quality improvement system using an active power filter (APF) must be considered. Due to the oscillating load current in the dynamic load condition, a fast and accurate harmonic current-tracking performance is required. As such, this paper proposes the design of a model predictive control (MPC) since the minimization of cost function in the MPC process can suitably determine APF switching states. The design technique of MPC is based on the APF mathematical model. This controller was designed to compensate the time delay in the digital control. Moreover, the synchronous detection (SD) method applied the reference current calculations, as shown in this paper. To verify the proposed MPC, the overall control of APF was implemented on a eZdsp F28335 board by using the hardware-in-the-loop technique. The testing results indicated that the proposed MPC can provide a fast and accurate harmonic current-tracking response compared with the proportional-integral controller. In the load changing condition, the MPC was still effective in providing a good result after compensation. The percentage of total harmonic distortion, the percentage current unbalance factor, and the power factor would also be kept within the IEEE Standard 519 and IEEE Standard 1459.

Detecting APT Attacks Based on Network Traffic Using Machine Learning

Advanced Persistent Threat (APT) attacks are a form of malicious, intentionally and clearly targeted attack. By using many sophisticated and complicated methods and technologies to attack targets in order to obtain confidential and sensitive information. In fact, in order to detect APT attacks, detection systems often need to apply many parallel and series techniques in order to make the most of the advantages as well as minimize the disadvantages of each technique. Therefore, in this paper, we propose a method of detecting APT attacks based on abnormal behaviors of Network traffic using machine learning. Accordingly, in our research, the abnormal behavior of APT attacks in Network Traffic will be defined on both components: Domain and IP. Then, these behaviors are evaluated and classified based on the Random Forest classification algorithm to conclude about the behavior of APT attacks. Details of the definition of abnormal behaviors of the Domain and IP will be presented in section 3.2 of the paper. The synchronous APT attack detection method proposed in this paper is a novel approach, which will help information security systems detect quickly and accurately signs of the APT attack campaign in the organization. The experimental results presented in section 4 will demonstrate the effectiveness of our proposed method.

Synchronous phase-shifting microscopic interference focal detection method based on wave aberration criteria

为了实时准确地将激光直写系统中经直写物镜聚焦的光斑定位于待加工元件表面，提出了一种基于波像差判据的同步相移显微干涉检焦方法，实现了对离焦量的实时检测与调整。在直写系统中引入检焦光路，与直写光路共享同一物镜，构建Linnik型同步相移显微干涉检焦系统，提取包含离焦量的波面相位信息；再从大数值孔径（<i>NA</i>）的物镜波像差数据中解析出离焦量的大小与方向。仿真结果验证了基于波像差判据的离焦计算方法的正确性，<i>NA</i>≥0.5时，离焦探测灵敏度可达4 nm, 通过实验验证了同步相移显微干涉检焦方法的可行性，检焦精度可达10 nm以内，满足激光直写高精度的测量要求。

Peculiarities of prismatic input of narrow-band radiation into Ag-ion diffusion waveguide

The peculiarities of prism coupling elements input and output of narrow-band radiation into ion diffusion waveguide are researched. Gradient waveguide with a thickness of 1.67 μm was formed by ion exchange in K8 glass. The output signal intensity dependence on the input and output angles of incidence radiation was measured by developed automatic hardware-software system based on synchronous detection method to improve the signal-to-noise ratio. It was shown the maximum of output signal is reached at equal input and output angles.