Adaptive Notch Filter Research Articles

Analysis and Suppression of Rotor Eccentricity Effects on Fundamental Model Based Sensorless Control of Permanent Magnet Synchronous Machine

In the past, various fundamental model based sensorless control methods have been proposed. However, most of them are developed under a healthy condition. Hence, in this article, fundamental model based sensorless control of permanent magnet synchronous machines (PMSM) under rotor eccentricity (RE) is investigated which is a common issue in many drive systems. It is known that under RE, three-phase back-EMFs, flux-linkages, inductances, and torque will be influenced. Mathematical derivation reveals that these effects will cause undesired harmonics in the position estimation. Since the frequencies of these low-order harmonics are much smaller than the bandwidth of position observer such as phase-locked loop, it is difficult to effectively eliminate them. Hence, the conventional back-EMF method is modified by adding an adaptive notch filter to suppress these undesired harmonics. Furthermore, the RE effects on PMSM characteristics are examined by measurements. The modified position estimator is implemented on a dSPACE platform and is verified by experiment results.

A new signal processing method for the nondestructive testing of a steel wire rope using a small device

Problems arise in the detection of defects in wire rope by magnetic flux leakage testing. The most obvious problems are that the excitation devices are cumbersome and inconvenient and the signal-to-noise ratio of damage signals is often low. This paper proposes a small detector. Compared with traditional detection devices, the proposed device has the advantages of a simple structure, easy installation, low weight and good portability. The weight of the device is only 508 g. The surface of the wire rope is characterized by wires and strands. The amplitude of the strand-waveform magnetic signal generated by the special helical structure of wire rope is larger than that of the defect signal. The magnetic image is processed using an adaptive spatial notch filter and the gradient method, and the detection results are analyzed. The strand-waveform magnetic signal cannot be completely eliminated, and not all defects can be detected. A new method is proposed to eliminate strand-waveform noise using the instantaneous phase solution in Hilbert transform and wavelet analysis. Experiments show that the proposed method suppresses noise well and detects and accurately locates all defects.

Adaptive Gaussian notch filter for removing periodic noise from digital images

Periodic noise corrupts digital images during acquisition and transmission stages by adding repetitive patterns. This study introduces a new adaptive Gaussian notch filter (AGNF) in Fourier transform domain for effectively restoring images contaminated with periodic, quasi-periodic and Moire pattern noises. Since periodic noises are sinusoidal functions added to the uncorrupted images, Fourier transform of images make these noisy functions to concentrate as easily distinguishable conjugate peaks in frequency domain. The proposed AGNF effectively identifies the noisy peak positions and adaptively quantifies the associated noisy areas by analysing the ratio of averages of frequencies from adaptively varying neighbourhoods. These identified noisy peaks are then diffused by Gaussian notch filter of adaptively varying sizes. The proposed filter ensures maximum diffusion of identified noisy peak areas by maintaining the minimum frequency values from the outputs of overlapping notch filters. Visual and quantitative experimental analysis of the proposed algorithm with mean absolute error, peak signal-to-noise ratio, mean structural similarity index measure and computation time reveals that AGNF is better in restoring images contaminated with periodic noises when compared to other methods.

An Assessment of Impact of Adaptive Notch Filters for Interference Removal on the Signal Processing Stages of a GNSS Receiver

With the fast growing diffusion of real-time high-accuracy applications based on the global navigation satellite system (GNSS), the robustness of GNSS receiver performance has become a compelling requirement. Disruptive effects can be induced to signal processing stages of GNSS receivers due to the disturbances from radio frequency interference (RFI), even leading to a complete outage of the positioning and timing service. A typical RFI threat to GNSS signals is represented by portable jammers, which transmit swept-frequency (chirp) signals in order to span the overall GNSS bandwidth. The implementation in the receivers of adaptive notch filters (ANFs) for chirp cancellation has been extensively investigated and proved to be an efficient countermeasure. However, the performance of the ANF is strongly dependent on its configuration setup. Inappropriate parameter settings of the ANF for interference removal may induce severe distortion to the correlation process. In addition, an effective mitigation will still introduce a vestigial signal distortion contributed by the residual unmitigated chirp and the ANF operation itself, being not negligible for high-accuracy solutions. This article addresses the detailed analysis for assessing the effects of interference mitigation by notch filtering. A bias compensation strategy is proposed, wherein for each pseudorandom noise, the biases due to parameter settings of the notch filter are estimated and compensated. The impact of using the ANF operation on chirp signals at the acquisition and tracking stages of GNSS receivers is analyzed. On the basis of the three proposed metrics, the effects can be quantitatively estimated to depict a complete picture of the most influential parameters of the chirp and the ANF configurations, as well as the optimal achievable performance at the acquisition and tracking stages.

A New PV-Open-UPQC Configuration for Voltage Sensitive Loads Utilizing Novel Adaptive Controllers

In this article, a novel topology for photovoltaic (PV) fed open unified power quality conditioner has been proposed focusing on the requirement of voltage sensitive loads. It has incorporated the advantages of open unified power quality conditioner (UPQC) and grid connected PV systems by providing a possible solution towards the demand of different power quality levels at end user. Increasing the system robustness for various voltage and current distortions, adaptive controllers have been implemented for series and shunt compensators of UPQC. Adaptive notch filter based improved Syncronous Reference Frame (SRF) scheme has been utilized for the control of series compensator. An adaptive logarithmic absolute algorithm has been implemented for shunt part of proposed system. The utilization of moving average filter (MAF) instead of low pass filter (LPF) for dc bus voltage regulation has neglected the chance of high as well as low frequency ripples. A feed forward component has been added to the shunt controller to regulate the grid current at constant level in presence of grid disturbances. The proposed controllers are verified on a developed prototype of proposed system in the laboratory. The system performance is found satisfactory under various grid conditions like voltage sags, voltage swells, voltage unbalance, voltage harmonics, sudden load addition and removal, and variation in solar irradiation.

A multi‐tone central divided difference frequency tracker with adaptive process noise covariance tuning

SummaryThe problem of real‐time frequency estimation of nonstationary multi‐harmonic signals is important in many applications. In this paper, we propose a novel multi‐frequency tracker based on a state‐space representation of the signal with Cartesian filters and the second‐order central divided difference filter (CDDF), which improves the performance of the extended Kalman filter (EKF) by using Stirling's interpolation method to approximate the mean and covariance of the state vector. A crucial element of the method is the adaptive scaling of the process noise covariance matrix appearing in the filter equations, as a function of the innovation sequence, which tunes the accuracy‐reactivity trade‐off of the filter. The proposed solution is evaluated against two approaches from the literature, namely the factorized adaptive notch filter (FANF) and the extended Kalman filter frequency tracker (EKFFT). Several experiments emphasize the estimation accuracy of the proposed method as well as the improved robustness with respect to initial errors and input signal complexity. The presented method appears to be particularly efficient with rapidly varying frequencies, thanks to the update mechanism that adjusts the filter parameters based on the amplitude of the estimation error.

Adaptive Complex Filtering for Narrowband Jamming Mitigation in Resource-Constrained Wireless Networks

Jamming attacks present a major challenge for the physical layer security of wireless communication systems. Among the large number of existing methods for jamming mitigation, filtering is a simple but promisingly effective solution that can be applied in resource-constrained and low-power wireless networks. In this article, a first-order adaptive complex narrowband notch filter is proposed for use against high-power narrowband jamming attacks. The central frequency of the filter is adaptively adjustable to match the interfering frequency. This enables the proposed solution to perform effectively in the presence of a jammer whose frequency varies in fixed or random time periods. The simulation results demonstrate the filter's behavior and the efficiency of the proposed technique.

Design and Analysis of Activation Strategies for Adaptive Notch Filters to Suppress GNSS Jamming

Adaptive notch filters (ANFs) have been widely investigated in literature for their low complexity and good performance, and used in many signal processing applications. More recently, they have been proven to be an effective solution against jamming interferences, considered more than ever a real threat to Global Navigation Satellite System signals. This article focuses on a specific family of ANF, where the adaptation algorithm is implemented as a frequency-lock-loop (FLL), namely FLL-equivalent ANFs. It presents the theoretical derivation of two detection approaches, namely power ratio-based and gradient-based, in charge of activating/deactivating such kind of filters. Both the theoretical and statistical analysis in case of swept-frequency jamming signals are provided. The performance evaluation for several interference-to-noise ratio conditions shows a tradeoff between the two solutions, with a slight advantage of the power ratio-based strategy. The results achieved in simulation clearly demonstrate that the proposed activation strategies can be combined with ANFs and that they can be effectively adopted for the mitigation of jamming signals.

Frequency tracking and mitigation method based on CPHD filter and adaptive multiple linear Kalman notch filter for multiple GNSS interference

NAVIGATIONVolume 67, Issue 1 p. 213-213 ERRATUMFree Access Frequency tracking and mitigation method based on CPHD filter and adaptive multiple linear Kalman notch filter for multiple GNSS interference This article corrects the following: Frequency tracking and mitigation method based on CPHD filter and adaptive multiple linear Kalman notch filter for multiple GNSS interference Sun Young Kim Chang Ho Kang Chan Gook Park Volume 66Issue 4Navigation pages: 803-830 First Published online: January 14, 2020 First published: 20 March 2020 https://doi.org/10.1002/navi.351AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onEmailFacebookTwitterLinked InRedditWechat In Kim et al,1 the Acknowledgements section was published with missing content. The text “This work was done while the first author was a member of the Department of Mechanical and Aerospace Engineering, Seoul National University.” should be added. The complete Acknowledgements section is shown below: ACKNOWLEDGEMENTS A preliminary version of this paper was presented at the ION GNSS+ 2018 conference. This work has been supported by the National GNSS Research Center program of the Defense Acquisition Program Administration and Agency for Defense Development, and the Ministry of Science and ICT of the Republic of Korea through the Space Core Technology Development Program (No. NRF- 2018M1A3A3A02065722). This work was done while the first author was a member of the Department of Mechanical and Aerospace Engineering, Seoul National University. The online version was already corrected. We apologize for this error. REFERENCE 1Kim SY, Kang CH, Park CG. Frequency tracking and mitigation method based on CPHD filter and adaptive multiple linear Kalman notch filter for multiple GNSS interference. NAVIGATION. 2019; 66(4): 803- 830. https://doi.org/10.1002/navi.332Wiley Online LibraryWeb of Science®Google Scholar Volume67, Issue1Spring 2020Pages 213-213 ReferencesRelatedInformation

Polarizing Voltage Generating Method for Distance and Directional Protection Elements

Distance and directional elements are widely used in power system protection. One of the used essential signals, having a substantial impact on proper operation, is polarizing voltage. During faults close to a protection relay, memory filters can be used to ensure the availability of this voltage. A basic assumption of these memory filters is that during a fault only an amplitude of a measured voltage changes rapidly and other parameters change very slow. The assumption is correct in power systems with an overwhelming share of traditional rotating generators. However, today, more and more energy sources are connected to power systems through inverters. Algorithms implemented in inverters can control parameters of output voltage so that they can be changed rapidly without any inertia. Therefore, a source of robust polarizing voltage is needed to ensure proper operation of distance and directional elements. The paper presents a method of a reference signal generation based on phase-locked loop (PLL). The algorithm consists of PLL with an adaptive notch filter, and elements adding inertia to the generated signal. The reference signal can be used as a polarizing voltage in protection elements. The paper describes all elements of the algorithm and presets operational tests.

Multiple Frequency Tracking and Mitigation Based on RSPWVD and Adaptive Multiple Linear Kalman Notch Filter

In this paper, the multiple frequency tracking and mitigation method based on the reassigned smoothed pseudo Wigner-Ville distribution (RSPWVD) and an adaptive multiple linear Kalman notch filter (AMLKNF) is proposed to track and mitigate multiple global positioning system (GPS) interference signals. Compared to the conventional notch filters, the AMLKNF has a faster convergence rate and smaller signal loss. However, for using this method, we need to know the notch frequency which is the interference frequency to remove. Thus, we use the RSPWVD method, one of the time-frequency analysis methods. In addition, an adaptation logic is designed in the AMLKNF to adjust the notch depth according to the power of the jamming signal. Matlab-based simulations are performed for analyzing the performance of the proposed method. The simulation results show that the proposed algorithm can efficiently track and eliminate interference well compared to the conventional methods.

Gain normalized adaptive observer for three-phase system

This paper proposes the estimation of parameters and symmetrical components of unbalanced grid using adaptive observer framework. Recent adaptive observers proposed in the literature doesn’t employ any gain normalization in their frequency estimation loop. This can be problematic in the presence of large voltage dip. This paper proposes a solution to overcome this limitation using a novel gain normalized - frequency-locked loop (GN-FLL). Technical details of GN-FLL, stability analysis and tuning are provided in this paper. Comparative experimental results with adaptive Luenberger observer, second-order generalized integrator - phase-locked loop (SOGI-PLL) and enhanced PLL (EPLL) are provided to demonstrate the effectiveness the proposed technique in the single-phase case. Comparative experimental results with double SOGI-FLL (DSOGI-FLL) and adaptive notch filter (ANF) are provided to demonstrate the effectiveness the proposed technique in the three-phase case.

A Novel Grid Synchronization Method Based on Hybrid Filter Under Distorted Voltage Conditions

The phase-locked accuracy of conventional phase-locked method is reduced when the grid voltage contains fundamental frequency negative sequence(FFNS) component, harmonic component, and DC offset component. Aiming at this problem, a novel adaptive notch filter (NANF) is proposed, and a dual NANF (DNANF) structure is designed to eliminate the FFNS component and extract the fundamental frequency positive sequence(FFPS) component based on NANF. Furthermore, dc DNANF with DC offset rejection capability is proposed by adopting DNANF. Then a novel hybrid filter in dq -frame is designed by combining dc DNANF and the cascaded delay signal cancellation operator filter whose delay parameters are 4 and 24 in dq -frame ( dq CDSC4,24). Meanwhile, a new SRF-PLL design method is proposed based on the novel hybrid filter. This proposed method employs dq CDSC4,24 to separate the positive and negative sequences of the voltage and eliminate the high frequency harmonics in the grid voltage, and uses dc DNANF to reject the DC offset, so as to achieve the accurate acquisition of the fundamental voltage information under distortion and unbalanced grid. Simulation and experimental results show that compared with the conventional SRF-PLL methods, the proposed method can obtain faster phase tracking speed, better phase-locked effect, faster dynamic response, and better stability.

A Method for Correcting Frequency Estimates for Synthetic Inertia Control

This paper presents three frequency estimation algorithms, one based on extended Kalman filtering, another on quadrature phase-locked loop and an adaptive notch filter. The paper proposes using some internal signals of these algorithms as an inverse reliability metric to determine the quality of the frequency estimate. The paper presents an algorithm to correct frequency estimates using these inverse reliability metrics. The algorithm is tested with signals with phase jumps and severe distortions. Accurate frequency estimates are of particular importance in real-time control applications. This paper shows the value of the proposed frequency correction algorithm in synthetic inertia (SI) control. It shows that for a test power system the corrector algorithm is critical in preventing the SI controller from erroneously injecting power that can exacerbate system faults.

Modeling and Adaptive Design of the SRF-PLL: Nonlinear Time-Varying Framework

Synchronous reference frame phase-locked loops (SRF-PLLs) are widely used in different technologies, such as wind turbines, electric vehicles, more electric aircraft, and motor drives, to estimate system's variables. The SRF-PLL is an adaptive notch filter that is used to estimate a sinusoidal signal's amplitude, phase angle, and frequency. However, when the input signal is subjected to a considerable variation or includes a significant noise, its stability and performance become challenging. In this paper, the stability of the SRF-PLL for substantial changes in the input signal's variables are investigated. To do so, the nonlinear time-varying (NTV) model of the system is proposed and is used for the large-signal stability assessment. Then, an adaptive tuning method, based on the proposed NTV model, is designed to improve its transient performance during and after the variation. Simulation and experimental results are used to validate the proposed method.

Disturbance Force Self-Sensing and Suppression Method for AMB-Rotor System Based on Disturbance Observer

This paper explores a disturbance force self-sensing and suppression method for active magnetic bearings (AMBs) system. Since the displacement of the AMB-rotor is affected by both the output of the controller and the disturbance force, the mathematical expression of the external disturbance force is deduced based on the inverse model of the controlled plant of the AMB-rotor system. The rotor displacement and output of the controller are both the input of the disturbance self-sensing system. A third-order low-pass filter is added to the self-sensing system so as to avoid the self-sensing system being unstable due to model uncertainty of the controlled plant. Then an adaptive notch filter added to the self-sensing system is used to eliminate the synchronous frequency component in the estimated disturbance. Finally, experiment results validate the proposed self-sensing method can effectively sense the external disturbance force within the range of about 67 Hz, and the AMB-rotor system can well suppress the disturbance force with the sensed value.

Mitigation of hand tremor using an active mass damper driven by an adaptive notch-filter based controller

Mitigation of hand tremor using an active mass damper driven by an adaptive notch-filter based controller

Frequency tracking and mitigation method based on CPHD filter and adaptive multiple linear Kalman notch filter for multiple GNSS interference

In this paper, a frequency tracking method based on a cardinalized probability hypothesis density (CPHD) filter with cardinality compensation and fuzzy-c means (FCM) clustering is proposed to precisely estimate multiple interference frequencies in the received Global Navigation Satellite System (GNSS) signal. In addition, an adaptive multiple linear Kalman notch filter is applied in order to mitigate multiple GNSS interference signals by using tracking results from the proposed CPHD filter. The cardinality refers to the number of interference frequencies, and estimation accuracy on the cardinality has an effect on the tracking and mitigation performance of the filter. For that reason, the cardinality compensation process and FCM clustering are added in the CPHD filter. The proposed tracking and mitigation method is evaluated by theoretical analysis including simulations. It is confirmed that the proposed algorithm has better tracking and mitigation performance compared with the conventional algorithms.

Single-Phase Frequency-Locked Loops: A Comprehensive Review

Synchronization techniques can be classified into open-loop and closed-loop methods. In power and energy applications, which are the focus here, the latter type is more popular. Phase-locked loops (PLLs) and frequency-locked loops (FLLs) are two broad categories of closed-loop synchronization techniques. The aim of this paper is providing a review of recent advances in designing single-phase FLLs, which can be very useful for both researchers and engineers. The historical development of a standard single-phase FLL, its modeling and tuning aspects, its relationship with adaptive notch filters, its advanced versions for the synchronization purposes under adverse grid conditions, its modification for different industrial applications, its connection with single-phase PLLs, and its discretization aspects are the main parts of this review.

Suppression of Synchronous Current Using Double Input Improved Adaptive Notch Filter Algorithm

In order to suppress the influence of the synchronous vibration generated by the unbalance of magnetically suspended control moment gyro on the attitude control accuracy and stability of the satellite platform, this article first introduces the working principle of the magnetically suspended high-speed rotor system, and also establishes the dynamic model of the magnetically suspended rotor with unbalance mass. At the same time, the main sources of unbalance vibration are also analyzed. Finally, an improved adaptive notch filter based on double input is designed. The filter takes the rotor radial X, Y two-channel displacement sensor signals as inputs, and uses the characteristics orthogonal to each other to simultaneously enter the system. The rotor can be automatically balanced by adjusting the convergence factor and the compensation angle to adaptively suppress the synchronous current in a widely operating speed range. Simulation and experimental results show that the method can effectively eliminate the synchronous current in a widely operating speed range and improve the stability of the system. This research on the microvibration of the rotor is of great significance and application value.