Multiple Notch Filter Research Articles

Design method for VDCC-based analog comb filter for power line interference cancellation

An analog comb filter is implemented by linking multiple VDCC-based notch filters in a cascading fashion (N in total), eliminating N different pole frequencies. This study focuses on suppressing a fundamental frequency of power-line interference of 50 Hz and its consecutive three odd harmonics at 150 Hz, 250 Hz, and 350 Hz. One significant advantage of this comb filter is the independent control over filters' parameters like quality factor and pole frequency. Additionally, these filters can be electronically tuned by adjusting the transconductance gain of VDCC. The suggested notch filter configuration involves 2 capacitors, 2 resistors, and 1 VDCC element. Extensive simulations were conducted using PSPICE simulator software to validate the effectiveness of these filters. The basic building block, VDCC, is designed and implemented in the simulation using integrated circuits MAX435 and AD844.•Design uses a VDCC-based high Q notch filter as the active building block.•The filter employs fewer active and passive components.•Simulated results using commercially available ICs, MAX435 and AD844, confirm the filter's practical utility.

Improved control of dynamic voltage restorer for compensation of unbalanced and harmonic-distorted grid voltage

Doubly fed induction generator (DFIG) are vulnerable to unbalanced voltage and harmonic distortion, which will lead to the heating problem of stator/rotor windings and the damage of gearbox. This paper establishes the transient modeling of the DFIG under composite unbalanced voltage and harmonic distortion condition, and elaborates the dynamic response of DFIG from the perspectives of rotor voltage, active power and reactive power under voltage harmonics and unbalance. It also presents an improved control strategy for a dynamic voltage restorer (DVR) to accurately track the specific voltage harmonics, with targeted consideration of constraining unbalanced voltage and fifth- and seventh-order voltage harmonics. The extractions of each voltage signals are presented in this paper via multiple notch filter (MNF), which has a good low-pass characteristic and an excellent performance in trapping the specific AC signals. The presented notch-filter-based algorithm has the advantages of simper control structure and faster response speed, and is more accurate in harmonic extraction. A 1.5-MW DFIG has been employed to establish the object of protection in simulation analysis to verify the validity of the proposed control strategy. The results show that the proposed control strategy is effective which is consistent with the theoretical model, and the oscillations of each crucial parameter can be well-suppressed.

Projection-Based Multiple Notch Filtering

A method for multi-frequency notch filtering is described. The approach is based on quadratic programming, which leads to projecting the signal vector onto the orthogonal complement of the subspace spanned by a set of sinusoidal basis vectors, each corresponding to a notch frequency. The projection matrix uses a weighted inner product whose weights are samples of a standard spectral analysis window. An overlap-add method suitable for block processing is also described. The projection-based notch filter (PNF) is compared with linear-phase FIR and IIR multiple notch filters and is found to have improved amplitude and phase distortion.

Real-Time Implementation of PV fed Universal Active Power Filter Using CF-SOGI based IPBT Control Scheme

This paper proposed a new control scheme of comb filter based second-order generalized integrator (CF-SOGI) in instantaneous power balance theory (IPBT) for photovoltaic (PV) fed universal active power filter (UAPF). The conventional SOGI frequency locked loop (SOGI-FLL) can provide good accuracy and fast dynamics, and better filtering abilities during idle grid conditions. To enhance the filtering ability and improve the accuracy under distorted conditions usually multiple notch filters are used. However, it suffers from a heavy computational burden due to the presence of multiple filters, the system becomes a complex structure and deteriorate dynamic performance. To overcome the above a comb filter is incorporated in the conventional SOGI-FLL. It extracts the frequency and fundamental positive component of voltage under adverse grid voltages. Along with it, a new IPBT control scheme generates the reference signals for UAPF using reference and load power calculations. It improves the dynamic performance by maintaining power balance in the system along with effective DC voltage regulation. The proposed system enhances the power quality issues on both source and load side as per IEEE-519 and integrates the PV into the utility grid on a two-stage topology. Also, it extracts the maximum power from the PV and delivers it to the load and grid connected at the point of interconnection (PIC). The system with the proposed control scheme is simulated on MATLAB/Simulink and the same is validated in the laboratory prototype experimental setup. The performance of a system is validated under grid voltage fluctuations, non-linear load, unbalance load, and change in irradiation conditions.

단시간 푸리에 변환과 전역 통과 필터 기반 노치 필터를 이용한 다중 주파수 제거 기법

This paper proposes a novel multiple frequency rejection technique based on the STFT (Short-Time Fourier Transform) and APNF (All-Pass filter-based Notch Filter). Because a non-adaptive multiple notch filter cannot track the target frequencies, an adaptive filter is often used. However, the existing adaptive notch filters cannot accurately identify the number of frequencies, which may deteriorate the filtering performance. Furthermore, a time-frequency analysis can be performed to simultaneously estimate the number of target frequencies and track them. Therefore, a novel adaptive multiple notch filtering method is developed, adopting the STFT at the front end of APNF. In particular, an interpolation scheme is adopted to compensate for the low frequency resolution of STFT. This framework exhibits a smaller amplitude response distortion for the pass-band compared to that in cascade-type multiple notch filters and can thus reject the time-varying frequencies. A MATLAB simulation is performed to verify the performance of the proposed method. The results confirm that the proposed scheme outperforms the conventional adaptive notch filter in removing chirp signals and temporary signals.

Influence of High Pass Filter Settings on Motor Evoked Potentials.

ObjectiveMotor evoked potentials (MEP), obtained by transcranial magnetic stimulation (TMS) are a common tool in clinical research and diagnostic. Nevertheless, reports regarding the influence of filter settings on MEP are sparse. Here, we compared MEP amplitudes and signal to noise ratio (SNR) using multiple high pass filter (HPF) and notch filter settings.Materials and MethodsTwenty healthy subjects were enrolled in the study. Recruitment curves were obtained with HPF settings varied at 10, 20, 50, and 100 Hz. The four HPF settings were tested both with and without 50 Hz active notch filter. Low pass filter was kept constant at 5 kHz.ResultsMEP amplitudes with HPF at 10 and 20 Hz were significantly higher than at 100 Hz, regardless of the notch filter. However, SNR did not differ among HPF settings. An active notch filter significantly improved SNR.ConclusionThe reduction in MEP amplitudes with HPF above 20 Hz may be due to noise reduction, since the different HPF conditions did not alter SNR. Thus, higher HPF above 50 Hz may be an option to reduce noise, the use of a notch filter may even improve SNR.SignificanceOur findings are relevant for the selection of filter settings and might be of importance to any researcher who utilizes TMS-MEP.

Multi-Frequency Interference Detection and Mitigation Using Multiple Adaptive IIR Notch Filter with Lattice Structure

Radio Frequency Interferences (RFI), such as strong Continuous Wave Interferences (CWI), can influence the Quality of Service (QoS) of communications, increasing the Bit Error Rate (BER) and decreasing the Signal-to-Noise Ratio (SNR) in any wireless transmission, including in a Digital Video Broadcasting (DVB-S2) receiver. Therefore, this paper presents an algorithm for detecting and mitigating a Multi-tone Continuous Wave Interference (MCWI) using a Multiple Adaptive Notch Filter (MANF), based on the lattice form structure. The Adaptive Notch Filter (ANF) is constructed using the second-order IIR NF. The approach consists in developing a robust low-complexity algorithm for removing unknown MCWI. The MANF model is a multistage model, with each stage consisting of two ANFs: the adaptive IIR notch filter Hl(z) and the adaptive IIR notch filter HN(z), which can detect and mitigate CWI. In this model, the ANF is used for estimating the Jamming-to-Signal Ratio (JSR) and the frequency of the interference (w(0)) by using an LMS-based algorithm. The depth of the notch is then adjusted based on the estimation of the JSR. In contrast, the ANF HN(z) is used to mitigate the CW interference. Simulation results show that the proposed ANF is an effective method for eliminating/reducing the effects of MCWI, and yields better system performance than full suppression (kN=1) for low JSR values, and mostly the same performance for high JSR values. Moreover, the proposed can detect low and high JSR and track hopping frequency interference and provides better Bit error ratio (BER) performance compared to the case without an IIR notch filter.

Frequencies estimation of gearbox vibration signal based on normalized lattice filter with RLS-based algorithm

In this paper, in order to estimate the meshing frequencies of a gearbox online, based on its vibration signal, an adaptive notch filter with a normalized lattice structure is proposed as an estimator. The notch filter exhibits a high degree of robustness and a low level of estimation errors, due to the minimal dynamic range of the node energies of the normalized lattice structure. A novel lattice recursive least square (NLRLS) algorithm, which introduces a correlation value between the vibration signal and the output signal of the estimation filter into the LRLS algorithm, is used as the adaptive algorithm for the notch filter. Theoretical analysis and simulation results show that the NLRLS algorithm exhibits greater stability than the LRLS algorithm for vibration signals where prior information is lacking. The meshing frequency estimation experiment is performed on a two-stage gearbox experimental platform. A triangular cascade structure is used to connect multiple notch filters to achieve multi-frequency estimation. The experimental results show that the notch filters can estimate meshing frequencies quickly and accurately, which verifies its effectiveness.

Parallel mode notch filters for vibration control of magnetically suspended flywheel in the full speed range

Undesired vibration force caused by harmonic currents is a common problem in a magnetically suspended flywheel (MSFW) rotor system. It poses a potential threat to system stability and performance degradation. In this work, multiple different phase-shift notch filters are connected in parallel mode to suppress the vibration harmonics. First, the multi-frequency vibrations in the MSFW is modelled and analysed. Then multiple different notch filters in parallel mode are proposed to plug into the baseline magnetically suspension system. The performance comparison with the conventional multiple notch filters is investigated. The parameters design and calculation for the proposed method are analysed in details. Moreover, the closed-loop stability of the overall system is given in the full speed range. Finally, simulation and experimental results for the MSFW demonstrate the superiority of the proposed method on both harmonics suppression and stability preservation.

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

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.

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.

Design of nearly linear‐phase double notch digital filters with close notch frequencies

In this study, the authors present a new procedure for the synthesis of the nearly linear-phase infinite impulse response (IIR) filters with two close notch frequencies based on all-pass filter application. The filter is obtained using a parallel connection of the delay line and IIR all-pass filter with a piecewise approximately linear phase. The desired magnitude characteristic is achieved by equiripple approximation of the all-pass filter phase. The magnitude characteristic is equiripple in all passbands. The proposed method is also suitable for the synthesis of complementary filters for extraction of the signal components at prescribed frequencies. The initial solution for the arbitrary order of an all-pass filter is proposed, which attains a sufficient number of phase error extrema. All phase error minima and maxima corresponding to the initial solution have almost identical values, excluding the ones near notch frequencies. As a result, the method exhibits fast and strong convergence. The described method can also be applied for the design of multiple notch filters with two very close notch frequencies.

Design of IIR Multiple-Notch Filters with Symmetric Magnitude Responses About Notch Frequencies

A novel all-pass-based infinite impulse response (IIR) digital multiple-notch filter design method is presented in this paper. The proposed method ensures that, for an arbitrary pass-bands ripple value, specifications regarding positions of notch, left- and right-hand cutoff frequencies are exactly met, which leads to symmetric magnitude responses about notch frequencies. Although iterative in its nature, proposed method requires a small number of iterations to find coefficients of the multiple-notch filter, making it very useful for designers. Since the magnitude response of the all-pass-based IIR multiple-notch filter is more sensitive in the stop-bands than in the pass-bands, sensitivity analysis along with simulation in limited word-length environment is performed.

Influence of flame dynamics on the optimal control of combustion with uncertainties

ABSTRACTA non-linear optimal control system is developed for attenuating thermos-acoustic pressure oscillations in a combustion chamber where the unsteady flow field associated with the internal instability is modelled in terms of a finite set of assumed modes of the non-linear in-homogeneously driven pressure wave field. A distributed set of auxiliary fuel injectors are used to control the thermo-acoustic pressure field with pressure measurements at independent locations. The mathematical model of the thermo-acoustic pressure field with multiple fuel injectors is developed. The flame dynamics is also modelled and its states are included in the design of the controller. Extensive simulations are performed to reveal the features of the thermo-acoustic pressure field within the combustion chamber and qualitatively compared with published data. The controller is synthesized on the basis of a non-linear quadratic Gaussian approach as well as a non-linear H∞ controller approach. The performances of the two controllers are compared. The influence of the flame dynamics is assessed by comparing the closed-loop performance by including the lag effects of a simplified flame transfer function. In particular it is shown that the non-linear H∞ controller approach is well-suited for the control of the combustion chamber pressure field as it has the structure of comb or multiple-notch filter and can attenuate acoustic tones associated with the combustion instabilities.

A Novel Design of Sparse FIR Multiple Notch Filters with Tunable Notch Frequencies

We focus on the design of finite impulse response (FIR) multiple notch filters. To reduce the computational complexity and hardware implementation complexity, a novel algorithm is developed based on the mixture of the tuning of notch frequencies and the sparsity of filter coefficients. The proposed design procedure can be carried out as follow: first, since sparse FIR filters have lower implementation complexity than full filters, a sparse linear phase FIR single notch filter with the given rejection bandwidth and passband attenuation is designed. Second, a tuning procedure is applied to the computed sparse filter to produce the desired sparse linear phase FIR multiple notch filter. When the notch frequencies are varied, the same tuning procedure can be employed to render the new multiple notch filter instead of designing the filter from scratch. The effectiveness of the proposed algorithm is demonstrated through three design examples.

Resonance characteristic analysis and damping control for LCL-filter-based voltage source converter during bus transfer

This paper investigates a new resonance issue of LCL-filter-based voltage source converters (VSCs). Unlike the traditional resonance issue under normal operating condition, the new potential issue is exposed in the application of automatic bus transfer system (ABTS), due to a temporary change of LCL filter structure during bus transfer. The resonance-induced current and voltage spikes may cause damage or nuisance tripping to sensitive equipment, leading to failure of the automatic transfer and interruption of the continuous process. To solve this problem, the transformation of resonance characteristics during bus transfer is analyzed in this paper. Furthermore, the influence factors to the system stability are obtained, and the stable regions of the factors are derived with Nyquist criterion. Besides, when the system parameters locate within the unstable region, a comprehensive damping scheme with an all-pass filter based multiple notch filter is proposed to solve both resonance issues. With the proposed damping strategy, a smooth bus transfer can be achieved without additional hardware. Finally, the experiments are provided to confirm the stability analysis and validate the effective damping scheme developed in this paper.

A novel cost-effective parallel narrowband ANC system with local secondary-path estimation

Many noise reduction applications are targeted at multi-tonal disturbances. Active noise control (ANC) solutions for such problems are generally based on the combination of multiple adaptive notch filters. Both the performance and the computational cost are negatively affected by an increase in the number of controlled frequencies. In this work we study a different modeling approach for the secondary path, based on the estimation of various small local models in adjacent frequency subbands, that greatly reduces the impact of reference-filtering operations in the ANC algorithm. Furthermore, in combination with a frequency-specific step size tuning method it provides a balanced attenuation performance over the whole controlled frequency range (and particularly in the high end of the range). Finally, the use of small local models is greatly beneficial for the reactivity of the online secondary path modeling algorithm when the characteristics of the acoustic channels are time-varying. Several simulations are provided to illustrate the positive features of the proposed method compared to other well-known techniques.

Analysis and design of notch filter-based PLLs for grid-connected applications

Using multiple notch filters (NFs) inside the control loop of a standard PLL is a basic strategy to improve its filtering capability. Often, adaptive NFs (ANFs) are employed for this purpose as they can block the disturbance components even under off-nominal grid frequencies. This advantage is at the cost of a rather considerable increase in the PLL implementation complexity and computational effort, particularly when ANFs have their own frequency estimation mechanism. The non-adaptive NFs (NNFs), contrary to ANFs, are easy to implement. They, however, have received a little attention in PLL applications. Therefore, their performance characteristics are rather unclear. To gain insight about the advantages and disadvantages of NNF-based PLLs (NNF-PLLs), analysis and design of these PLLs is conducted in this paper. This procedure includes: (1) selecting the appropriate number of NNFs inside the PLL control loop, (2) approximating dynamics of cascaded NNFs with a simple first-order low-pass filter, which simplifies the tuning procedure, (3) applying the symmetrical optimum method for selecting the control parameters of the NNF-PLL, and (4) performing extensive experimental results. The obtained results indicate that NNFs can sufficiently mitigate disturbances caused by the presence of harmonics in the PLL input while maintaining a fast dynamic response for the PLL. To be more exact, the NNF-PLL can provide a settling time around 2 cycle of the nominal frequency during phase and frequency jumps while having a peak-to-peak phase error less than 0.2° under a heavily distorted grid condition (THD=15%). It, however, may not be able to effectively reject the double-frequency disturbance component caused by the grid voltage unbalance. To deal with this problem, a hybrid combination of adaptive/nonadaptive NFs is suggested in this paper. The experimental results show that the resultant PLL, which is called the HNF-PLL, completely removes the grid voltage unbalance, effectively suppresses harmonics, and offers a fast dynamic response (a settling time around 1.5 cycle of the nominal frequency). The ease of implementation is kept in the HNF-PLL as only one of the NFs is adaptive and this NF does not require a separate frequency estimation mechanism.

Multiple band notch and Dual-Band filter using concentric and contiguous split ring resonators (CCSRR)

A novel, compact, multiple band notch filter and dual-band filters are presented. Contiguous and concentric split ring resonators (SRRs) and Ring resonator are used to achieve desired multiple narrow band notches. These band notches have been designed to avoid the undesired interference between co-existing wireless channels. The dual-band filter consists of a dual SRR having splits on the opposite sides with Inductive Short Stub Split Ring Resonator. Even- and odd-mode analyses have been performed to calculate the resonance frequencies. Three transmission zeros are achieved between the two passbands by both dominant electric or dominant magnetic coupling and also cancellation effect of electric and magnetic coupling. This results in high passband selectivity and improved band-to-band isolation. The proposed dual-band pass filter has the advantages of being compact with more degree of freedom to achieve desired passbands by controlling the electric and magnetic coupling independently. Proposed filter is implemented on RT/Duroid 5880 (εr = 2.2) substrate of thickness 0.785 mm and surface area of 0.27λg × 0.27λg. Insertion loss of the proposed filter at notch bands is high (>13 dB) and low (<0.8 dB) in pass band. Measured results correlate with the simulated results and thus ensure that the proposed filter is a suitable candidate to mitigate interference caused by the co-existing and emerging wireless technologies.