Suppression Scheme Research Articles

Design of a Multi-Position Alignment Scheme.

The current new type of inertial navigation system, including rotating inertial navigation systems and three-autonomy inertial navigation systems, has been increasingly widely applied. Benefited by the rotating mechanisms of these inertial navigation systems, alignment accuracy can be significantly enhanced by implementing IMU (Inertial Measurement Unit) rotation during the alignment process. The principle of suppressing initial alignment errors using rotational modulation technology was investigated, and the impact of various component error terms on alignment accuracy of IMU during rotation was analyzed. A corresponding error suppression scheme was designed to overcome the shortcoming of the significant scale factor error of fiber optic gyroscopes, and the research content of this paper is validated through corresponding simulations and experiments. The results indicate that the designed alignment scheme can effectively suppress the gyro scale factor error introduced by angular motion and improve alignment accuracy.

FLC-Based Ultra-Low-Frequency Oscillation Suppression Scheme for Interconnected Power Grids

The appearance of ultra-low-frequency oscillations in the grid at the sending end, after asynchronous grid interconnection, poses a significant threat to the stable operation of the system. For post-asynchronous interconnection in a multi-DC transmission system, an investigation is conducted to analyze the causes of ultra-low-frequency oscillations and the utilization of a Frequency Limit Controller (FLC) which aims to suppress these oscillations. Furthermore, a method is developed to rank DC sensitivity, considering the hydroelectric distribution in the sending-end grid, by combining the DC FLC impact factor and DC control sensitivity. Subsequently, a novel approach for ultra-low-frequency oscillation suppression is proposed. This approach employs the stochastic subspace method for parameter estimation and the NSGA-II optimization algorithm to convert the multi-DC optimization challenge into multiple sequential cyclic optimization problems, each focusing on a single DC, ensuring a more effective suppression of ultra-low-frequency oscillations. The proposed scheme’s effectiveness is validated through simulations using a specific locations’ interconnected power grid.

Field-programmable gate array-based residual amplitude modulation suppression and control for compact atomic clocks.

We designed a field-programmable gate array (FPGA) fabric to provide phase modulation techniques to lock lasers to optical frequency references. The method incorporates an active residual amplitude modulation (RAM) suppression scheme that relies on complex modulation. All the required servos to construct an optical atomic clock are incorporated into the same low-cost, commercial FPGA chip. We demonstrate a reliable, long-term RAM suppression of 60 dB with the remaining RAM level at -100 dBc and an improved stability of three decades when applied on a two-photon rubidium clock.

Slice through the water-Exploring the fundamental challenge of water suppression for benchtop NMR systems.

Benchtop NMR provides improved accessibility in terms of cost, space, and technical expertise. In turn, this encourages new users into the field of NMR spectroscopy. Unfortunately, many interesting samples in education and research, from beer to whole blood, contain significant amounts of water that require suppression in 1H NMR in order to recover sample information. However, due to the significant reduction in chemical shift dispersion in benchtop NMR systems, the sample signals are much closer to the water resonance compared to those in a corresponding high-field NMR spectrum. Therefore, simply translating solvent suppression experiments intended for high-field NMR instruments to benchtop NMR systems without careful consideration can be problematic. In this study, the effectiveness of several popular water suppression schemes was evaluated for benchtop NMR applications. Emphasis is placed on pulse sequences with no, or few, adjustable parameters making them easy to implement. These fall into two main categories: (1) those based on Pre-SAT including Pre-SAT, PURGE, NOESY-PR, and g-NOESY-PR and (2) those based on binomial inversion including JRS and W5-WATERGATE. Among these schemes, solvent suppression sequences based on Pre-SAT offer a general approach for easy solvent suppression for samples with higher analyte concentrations (sucrose standard and Redbull™). However, for human urine, binomial-like sequences were required. In summary, it is demonstrated that highly efficient water suppression approaches can be implemented on benchtop NMR systems in a simple manner, despite the limited spectral dispersion, further illustrating the potential for widespread implementation of these approaches in education and research.

A Novel Torque Ripple Suppression Scheme of Switched Reluctance Motors Based on Unipolar Sinusoidal Current Excitation

A Novel Torque Ripple Suppression Scheme of Switched Reluctance Motors Based on Unipolar Sinusoidal Current Excitation

Ultra-clean pure shift NMR with optimal water suppression for analysis of aqueous pharmaceutical samples.

Pure shift NMR experiments greatly enhance spectral resolution by collapsing multiplet structures into singlets and, with water suppression, can be used for aqueous samples. Here, we combine ultra-clean pure-shift NMR (SAPPHIRE) with two different internally encoded water suppression schemes to achieve optimal performance for small molecule and macrocyclic peptide pharmaceuticals in water and acetonitrile-water mixtures.

An Effective Range Ambiguity Suppression Scheme for Multistatic SAR Constellations Based on Multiechoes Coherent Processing

An Effective Range Ambiguity Suppression Scheme for Multistatic SAR Constellations Based on Multiechoes Coherent Processing

Signal Enhancement and Suppression Schemes for Bi-Static ISAC with IRS-Mounted Target

Signal Enhancement and Suppression Schemes for Bi-Static ISAC with IRS-Mounted Target

Harmonics Reduction in Virtual Synchronous Generator Using Fuzzy Logic controller

Harmonics are always present in the electrical networks in both no-load and load conditions. Harmonics reduces the power quality of the VSG in the presence of nonlinear loads and distorted grid. Completely removing the Harmonics from the network is impossible but we need to reduce them to a minimum value so that the system efficiency improves. A hybrid harmonic suppression scheme is proposed to enable the further improvement of the adaptability of VSG, which mainly consists of a voltage harmonic control loop and a grid current-controlled loop. The voltage harmonic control loop aims to scale down the inverter output impedance via a negative feedback loop, while the grid current-controlled compensator is intended to counteract the adverse effects from a weak grid via an additional voltage, which leads to substantially lower total harmonic distortion for both the load voltage and the grid current at the same time .By using a proper controller we can reduce the THD value of the grid to the minimum.

RFI Suppression Scheme for Complicated Low-Rank Violation Cases

RFI Suppression Scheme for Complicated Low-Rank Violation Cases

Modelling and suppression of bearing voltage of wind turbine permanent magnet synchronous generators

AbstractThe problem of bearing current is common in wind power generation system, which leads to the attenuation of generator life and great economic losses. Bearing voltage of a 5.5 MW wind‐turbine permanent magnet synchronous generator is studied. The bearing voltage equivalent circuit is modelled by studying the internal system structure of the generator, and an extraction method of cable parameters, generator winding parameters and stray capacitance parameters based on experiments is proposed to simulate the system. A system test platform is built to test the common mode voltage, common mode current and bearing voltage, and the test results are compared with the simulation results in time domain and frequency domain. The result indicate that the common mode equivalent model can accurately simulate the actual bearing voltage. Finally, rotor flange insulation is adopted to suppress bearing voltage. The relationship between the design of rotor flange insulation with suppressing effect is discussed. Finally, an optimisation design method is presented for the proposed suppression scheme.

Modelling of high frequency bearing voltage for dual‐winding permanent magnet synchronous generators

AbstractThe modelling and analysis of high‐frequency bearing voltage are of great significance to the assessment and mitigation of the electrical erosion risk in wind power systems. However, the dual‐winding permanent magnet synchronous generator (DW‐PMSG), as one of the mainstream models in wind power industry, has not been specifically analysed for its bearing voltage modelling method in the existing research. The high frequency common mode equivalent circuit model of DW‐PMSG is established, and the effect of parasitic parameters between two sets of winding on bearing voltage is analysed. A model parameters extraction method based on differential evolution algorithm is proposed, and the range of parameters is estimated by finite element simulation and test results, which improves the search efficiency and solution accuracy. The accuracy of the proposed model is verified by the comparison of simulation and experimental results. On this basis, it is possible to conduct more in‐depth research on the bearing voltage and bearing currents of DW‐PMSG, and provide theoretical basis and simulation means for the design of suppression schemes.

Experimental study on the wave-induced fluid resonance and suppression scheme in the narrow gap of two floating rectangular structures

An experimental study on the wave-induced gap resonance and resonant suppression scheme for two floating rectangular structures (TFRSs) is systematically presented. The instantaneous velocity fields for the present problem are measured using an enhanced underwater particle image velocimetry measurement system. Detailed experimental results have been presented to study the influences of the wave and structural parameters on the gap resonant characteristics. The resonant wave height and wave frequency were sensitive to the variation of the gap width but not very sensitive to the variation of the surface roughness on the rounded corner of TFRSs. The nonlinear effects of harmonic components on resonant free surface elevation are estimated. To analyze the vortex structures, different vortex identification methods in literature are analyzed and their merits and demerits are summarized based on a comparative analysis of the measured velocity data. The Ω-criterion vortex identification approach is then selected to evaluate the vortex intensity and capture the main vortex cores. Thanks to the adopted technique, the subsequent separation of the two quasi-symmetric vortex structures is considered to be a significant contribution to energy dissipation. The vortex shedding and dissipation modes of different TFRSs are very similar and exhibit slight variations in resonant responses. A formula of the modified Reynolds number for the gap resonance problem of TFRSs is proposed. The non-dimensional vortex strengths are nonlinearly dependent on the newly modified Reynolds number and linearly dependent on the Keulegan–Carpenter (KC) number. Finally, an optimal suppression scheme for the gap resonance problem of TFRSs is suggested.

Bidirectional Precharge and Negative Bias Scheme for Program Disturbance Suppression in 3-D NAND Flash Memory

Bidirectional Precharge and Negative Bias Scheme for Program Disturbance Suppression in 3-D NAND Flash Memory

Low-Frequency Current Ripple Minimization of Single-Star Bridge Cells-Based Battery Energy Storage System Using Optimal Third Harmonic Voltage Injection

Single-star bridge cell (SSBC) based multilevel converters are a promising solution for constructing high-voltage and large-capacity battery energy storage systems (BESSs) in power systems. Nevertheless, an undesirable second harmonic current (SHC) will be generated in the battery units since the single-phase instantaneous power of the SSBC pulsates at twice the line frequency. Such SHC-dominated low-frequency current ripple not only shortens the lifespan of the BUs but also degrades the system's efficiency. However, this intrinsic issue is overlooked in recent studies. To this end, an SHC suppression scheme that makes full use of the residual modulation index of the system to inject an optimal third harmonic voltage (THV) is proposed. The phase of the THV is determined first, followed by a closed-loop control strategy to regulate its magnitude dynamically for achieving a minimum SHC within the modulation constraints. The scheme is implemented with the variables that already existed in the main control system, resulting in a low increase in cost. The adverse impact of the technique on the AC-side output characteristics is investigated quantitatively, and a modified design procedure for the DC filter network is presented to address this issue. Hardware-in-the-loop experiments are carried out to validate the technique.

Analysis of Offline Transient Power Oscillation and Its Suppression Method in the Microgrid with Multiple Virtual Synchronous Generators

When multiple Virtual Synchronous Generators (VSGs) operate in parallel in an islanded grid, power and frequency oscillations will occur when one VSG goes offline. However, the existing literature does not cover the related analysis and transient suppression schemes for this scenario. To analyze these complex high-order system dynamics, this paper first establishes an intuitive equivalent circuit model for multiple VSGs, and the frequency domain expressions of the multi-machine VSG system during the VSG offline transient simulation are then derived. Based on the multi-VSG model and its transient oscillations analysis, this paper further proposes a configuration scheme for the equivalent circuit parameters. Equivalently, the virtual inertia, damping coefficient and virtual impedance of the VSGs can be configured. With the proposed parameter configuration scheme, the power oscillation during the VSG offline transient can be eliminated, as verified by experiments with a microgrid lab platform using three VSGs. Compared with the existing multi-VSG studies, the proposed scheme is not only the first attempt to study the transient suppression when a VSG goes offline, but also is more intuitive in analysis and less complicated in the controller parameter tuning.

CHATTER SUPPRESSION FOR ROBOTIC MILLING USING A NOVEL MAGNETORHEOLOGICAL FLUID ABSORBER

Industrial robots are more compliant than CNC machine tools, which makes them prone to chatter during robotic milling. Chatter has slowed down the adoption or sometimes inhibited the use of robots for machining tasks. This work presents a new chatter suppression scheme by mounting a magnetorheological fluid (MRF) absorber on the spindle housing to absorb the vibration with a specific frequency range. Firstly, a Gaussian process regression (GPR) model is used to predict the modal parameters at different machining positions. Subsequently, the predicted modal parameters are employed as input to obtain the transfer matrix for chatter frequency calculation. After that, a novel MRF absorber is designed based on the controllable shear modulus of the MRF in its pre-yield region. The simulation verifies that the designed MRF absorber can suppress chatter and thus improve the surface quality of the workpiece.

An Extended Active Resonance Suppression Scheme Based on a Dual-Layer Network for High-Performance Double-Inertia Drive System

An Extended Active Resonance Suppression Scheme Based on a Dual-Layer Network for High-Performance Double-Inertia Drive System

Pulse-efficient quantum machine learning

Quantum machine learning algorithms based on parameterized quantum circuits are promising candidates for near-term quantum advantage. Although these algorithms are compatible with the current generation of quantum processors, device noise limits their performance, for example by inducing an exponential flattening of loss landscapes. Error suppression schemes such as dynamical decoupling and Pauli twirling alleviate this issue by reducing noise at the hardware level. A recent addition to this toolbox of techniques is pulse-efficient transpilation, which reduces circuit schedule duration by exploiting hardware-native cross-resonance interaction. In this work, we investigate the impact of pulse-efficient circuits on near-term algorithms for quantum machine learning. We report results for two standard experiments: binary classification on a synthetic dataset with quantum neural networks and handwritten digit recognition with quantum kernel estimation. In both cases, we find that pulse-efficient transpilation vastly reduces average circuit durations and, as a result, significantly improves classification accuracy. We conclude by applying pulse-efficient transpilation to the Hamiltonian Variational Ansatz and show that it delays the onset of noise-induced barren plateaus.

The time invariant beamformer for Doppler spread suppression in high‐mobility transmission

AbstractBeamforming network with the Doppler suppression scheme reducing the channel time‐varying effects has attracted much research interests in high‐mobility massive MIMO communications. However, the current time‐varying beamforming network still suffers from high volatility peak‐to‐average power ratio (PAPR) fluctuations. For this reason, a time invariant compensation optimized beamformer is proposed to mitigate the peak‐to‐average power ratio high volatility and the channel time variation in the high‐mobility uplink transmission. To attain the Doppler spread and implement the Doppler spread suppression scheme, a time‐varying spectrum (TVS) is proposed and its statistical properties of time‐varying spectrum is analyzed. The simulation results are provided to verify the proposed studies.