Adaptive Notch Filter Research Articles

Finite Control Set Model Predictive Control for Dynamic Reactive Power Compensation With Hybrid Active Power Filters

This paper applies finite control set model predictive control (FCS-MPC) for dynamic reactive power compensation using a hybrid active power filter (HAPF). The FCS-MPC uses a model based on LCL -filter equations to predict the system behavior and optimize the control action. In fact, the application of FCS-MPC in grid-connected converters with LCL -Filter is quite recent. This algorithm is a very promising control technique for power electronics converters and its use for reactive power control of hybrid filter has not been reported in the literature yet. This paper uses the FCS-MPC in a multivariable structure along with an adaptive notch filter to damp resonance. The main purpose is to improve the dynamic response of the HAPF. Simulation as well as practical results prove the feasibility of FCS-MPC application in HAPF reactive power control. The dynamic response of the equipment was significantly improved and represents the main contribution of this paper. As a result, the FCS-MPC allows tracking fluctuations and abrupt changes in load reactive power.

Analysis of Power System Oscillations From PMU Data Using an EPLL-Based Approach

Recently, the application of the adaptive notch filter (ANF) concept to the analysis of damped oscillations and the estimation of frequency and damping factor of such oscillations was introduced. This paper presents the application of the enhanced phase-locked loop (EPLL) to the same problem. A modified version of the EPLL is developed that includes the estimation of damping factor in addition to the already estimated variables of amplitude, phase angle, and frequency. The structure, mathematical formulation, and theoretical stability analysis of the proposed method, including guidelines for its parameter tuning, are presented. Simulation results verify the analytical derivations and the desirable performance of the proposed method. This paper concludes that the EPLL-based approach can address the problem as efficient as the ANF approach while offering more robust and accurate results at low sampling rate applications.

Variable step‐size oscillator‐based adaptive notch filer algorithm using maximum correntropy criterion

A novel oscillator-based adaptive notch filter (OSC-ANF) algorithm is presented. The proposed algorithm has robustness against the impulsive noise because it is derived by using the maximum correntropy criterion (MCC). In addition, the variable step-size MCC-OSC-ANF algorithm is proposed to improve the frequency estimation performance. Experimental results show that the proposed algorithms perform better than the previous algorithm under impulsive noises.

Knowledge-Based Generalized Side-Lobe Canceller for Ionospheric Clutter Suppression in HFSWR

High frequency surface wave radar (HFSWR) has been successfully developed for early warning and remote sensing. However, the ionospheric clutter is a difficult challenge that can make HFSWR system inefficient. The Generalized Side-lobe Canceller (GSC) has been proved to be an effective algorithm for clutter suppression in theory, but it suffers from the performance degradation for some non-ideal conditions in practice. The most intolerable shortcoming is the signal to noise ratio (SNR) loss caused by the residual signal in the secondary data. In this paper, a knowledge-based GSC (KB-GSC) method has been proposed via an adaptive single notch filter design to reject the residual signal for reducing the SNR loss. The feasibility and availability has been demonstrated by measured data.

Adaptive Control and Predictive Control for Torsional Vibration Suppression in Helicopter/Engine System

In order to damp torsional vibrations in a helicopter, which would cause resonance in rotating components like engine, transmission, and rotor, an adaptive notch filter is proposed. Instead of fixed notch filter, the adaptive one, with FFT analyzer and sorting algorithm, can damp the low-order torsional vibration signal with natural frequency varying in a wide range. Then, in order to enhance the power following capability of the engine, a nonlinear model predictive controller based on the supported vector machine is designed to compensate for the dynamic control performance. Through the adaptive notch filter, the torsional vibration of the free turbine speed whose frequency is away from the set-point value can effectively be suppressed by 50% compared with the fixed notch filter. Furthermore, instead of conventional PID controller, the nonlinear model predictive controller based on the adaptive notch filter can reduce the sag of the free turbine to less than 0.4%. Therefore, the control strategy achieves fast high-quality response of the turbo-shaft engine.

Soft-Switched High Voltage Gain Boost-Integrated Flyback Converter Interfaced Single-Phase Grid-Tied Inverter for SPV Integration

A two-stage grid-tied efficient solar photovoltaic (SPV) system with zero voltage switching (ZVS) and zero current switching (ZCS) at the dc–dc converter stage and adaptive synchronization at the inverter stage is proposed. In the first stage, an improved high step-up boost-integrated flyback converter with quasi resonant voltage multiplier cell is proposed. ZVS turn-on of all mosfet s and ZCS turn-off of all diodes of resonant voltage multiplier cell results in high efficient power conversion compared with the conventional boost-integrated flyback converters. Small-sized coupled inductor enhances magnetic utilization in this converter. Second stage consists of a single-phase H-bridge grid interfaced inverter with variable band hysteresis current control technique. Amplitude adaptive notch filter is used to extract fundamental unit voltage vector of grid voltage required for estimation of synchronized reference current for hysteresis controller. A 250 W laboratory prototype is developed and experimentally evaluated. Experimental results demonstrate efficient renewable energy conversion at dc–dc converter stage and quality power injection at dc–ac inverter stage of the proposed grid-tied SPV system under changing solar insulation levels.

A Comparative Performance Evaluation of Extended AANF with Different Parameter Estimation Techniques for Renewable Energy Integration

This paper presents real time performance evaluation of three phase extension of an amplitude adaptive notch filter (AANF) for online estimation of frequency, amplitude, and sequence components of the input grid voltage signal. The performance of an extended AANF is compared with conventional synchronous reference frame-phase lock loop (SRF-PLL), enhanced phase lock loop (EPLL), and existing adaptive notch filter (ANF). Comparative analysis has been carried out based on their ability in extracting frequency and amplitude of input grid voltage signal under balanced and unbalanced voltage sag/swell, frequency shift and distorted grid condition. Three phase AANF method provides high degree of accuracy than SRF-PLL, EPLL, and ANF in extracting appropriate signal information for unbalanced and harmonically distorted grid condition. The important feature of this method is its amplitude adaptability, which improves its speed of response and accuracy when grid signal is of variable amplitude. OPAL-RT’s (OP4500) real time controller with an in-built Xilinx Kintex-7 FPGA processor is used for real time implementation. Experimental results validate fast and accurate performance of an extended AANF in extracting frequency, amplitude, and sequence components of the utility grid voltage signal, which can be further used for performance improvement of grid connected renewable energy systems, custom power devices, and flexible ac transmission systems (FACTS) devices.

Research on passive detection parameter measurement technology based on single vector sensor

Passive detection as a major function of the sonar system, over the years has been the work of waterborne workers to solve the problem. This paper mainly talks about the measurement technology of passive detection parameters based on single vector sensor. The problem of low frequency line spectrum signal extracted from ship radiated noise is studied, and the azimuth sequence and frequency sequence are obtained by estimating and analyzing the low frequency line spectrum signal. Ship radiated noise contains a lot of target information, so the extraction of the line noise of the ship's radiated noise is of great significance in the measurement of passive detection parameters. The radiation noise of the ship is a broadband spectrum modulated by the spectral signal envelope. The average azimuth and complex intensifier are used to estimate and analyze the target azimuth, and the estimated angle is statistically processed by histogram and weighted histogram. For the frequency estimation technique, the adaptive frequency estimator based on the adaptive notch filter and the adaptive LMS (Least Mean Square) algorithm is chosen to study the target signal frequency. Through the simulation experiment, the azimuth estimation technique and the adaptive frequency estimation technique are feasible. By estimating the azimuth sequence and frequency sequence of the target radiation signal, the relevant information of the target can be obtained, so it is of great significance in the research of underwater acoustic detection technology.

Grid Interfaced Distributed Generation System With Modified Current Control Loop Using Adaptive Synchronization Technique

This paper presents real-time implementation of a grid interfaced distributed generation (DG) system with modified current control loop using three phase amplitude adaptive notch filter (AANF) based synchronization tool. A grid current feedback based modified $dq$ -current control technique for interfacing inverter is developed in order to achieve constant loading on the grid, transient-free operation, and power factor improvement close to unity power factor (UPF) of the utility grid during sudden load variations. This technique does not require separate calculation of reference reactive component and harmonics component of currents hence reduces control circuit complexity. In addition, it requires only three voltage and three current sensors. Three phase AANF is developed and is used for online extraction of utility voltage phase angle to generate synchronized reference current signals for interfacing inverter. AANF is used because of its adjustable accuracy and amplitude adaptability even under unbalanced voltage sag and swell, frequency variation, and distorted grid conditions. Fast and accurate behavior of three phase AANF improves the dynamic response of entire DG system control performance for sudden load variations. The dynamic behavior of the proposed grid interfaced DG system is experimentally evaluated in maintaining constant loading on grid, transient-free operation, and power factor improvement close to UPF operation of the utility grid, by compensating total reactive power and harmonic current demanded by variable linear as well as nonlinear load.

Adaptive notch filter design for levitation sensing system based on vibration computation

In this study, to suppress the vehicle-guideway coupled vibration with variable frequencies, an adaptive notch filter is designed for a maglev train on different elastic supporting beams at a low speed. By the analysis of the vibration signals from sensors of suspension control system, the effective frequency band of the vibration signals is determined firstly. Then the vibration frequency is real-time searched and identified with high resolution as the center frequency of a small effective bandwidth notch filter. Finally, the designed adaptive notch filter with the identified signal frequency, which always runs automatically, is used in a closed-loop control system of permanent-electro magnetic suspension-type maglev train. Theoretical analysis and simulation experiments show that the adaptive notch filter can restrain the resonance phenomenon on different elastic supporting beams effectively.

ACTIVE VIBRATIONAL CONTROL OF FLEXIBLE MANIPULATOR USING FILTERED-X LMS ALGORITHM

This paper describes the vibration control of a flexible manipulator using Filtered-x LMS algorithm. In this study adaptive notch filter is applied to the vibration control of a flexible manipulator model. The adaptive notch filter is designed to estimate multiple vibration mode frequencies of the flexible manipulator and to minimize the effect of vibration. The filtered-x LMS algorithm is applied to make the root strain error and the system input as close to minimization as possible. In the process, the adaptive notch filter learns to eliminate the resonant vibration frequencies of the system. The experimental results show that this presented adaptive notch filter system can suppress the vibration of the flexible manipulator and track the desired joint angles.

Adaptive notch filter design under multiple identical bandwidths

Digital notch filters are applied to remove or suppress the narrow-band interferences in digital signals, while preserving other components unchanged. Under the condition of the identical notch bandwidths, a novel design method is put forward in this paper to realize the adaptive notch filter with infinite-impulse response (IIR). Firstly, a specially simplified all-pass filter is introduced to construct an IIR non-adaptive notch filter, which serves as the core part in the adaptive one. Secondly, the criterion of least-mean-square (LMS) is applied to design the desired adaptive notch filter (ANF). The designed ANF can track and suppress multiple non-harmonic interference components simultaneously. Finally, the effectiveness and practicability of the proposed design method are verified by a set of experimental results.

A Novel Complex-Coefficient In-Band Interference Suppression Algorithm for Cognitive Ultra-Wide Band Wireless Sensors Networks.

With the rapid development of wireless communication systems and electronic techniques, the limited frequency spectrum resources are shared with various wireless devices, leading to a crowded and challenging coexistence circumstance. Cognitive radio (CR) and ultra-wide band (UWB), as sophisticated wireless techniques, have been considered as significant solutions to solve the harmonious coexistence issues. UWB wireless sensors can share the spectrum with primary user (PU) systems without harmful interference. The in-band interference of UWB systems should be considered because such interference can severely affect the transmissions of UWB wireless systems. In order to solve the in-band interference issues for UWB wireless sensor networks (WSN), a novel in-band narrow band interferences (NBIs) elimination scheme is proposed in this paper. The proposed narrow band interferences suppression scheme is based on a novel complex-coefficient adaptive notch filter unit with a single constrained zero-pole pair. Moreover, in order to reduce the computation complexity of the proposed scheme, an adaptive complex-coefficient iterative method based on two-order Taylor series is designed. To cope with multiple narrow band interferences, a linear cascaded high order adaptive filter and a cyclic cascaded high order matrix adaptive filter (CCHOMAF) interference suppression algorithm based on the basic adaptive notch filter unit are also presented. The theoretical analysis and numerical simulation results indicate that the proposed CCHOMAF algorithm can achieve better performance in terms of average bit error rate for UWB WSNs. The proposed in-band NBIs elimination scheme can significantly improve the reception performance of low-cost and low-power UWB wireless systems.

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.

An Efficient Narrowband Interference Suppression Approach in Ultra-Wideband Receiver

Ultra-wideband (UWB) radio will be sharing the propagation environment with other pre-existing wireless systems, some possibly creating UWB multiple access interference, and others creating narrowband interference in the UWB radio bands. The Federal Communications Commission regulations have set conditions that limit the interference from the UWB radiators to other wireless systems, however, the issue of eliminating interference to the UWB radios from the pre-narrow band interference existing system is left to the ingenuity of the UWB radio designer. To optimize the performance of UWB wireless communication systems deteriorated by strong narrowband interferences, a high-efficiency interference suppression scheme is proposed in this paper. The closed-form weight coefficient iteration expression of basic adaptive notch filter cell with two constrained zero-pole pairs is derived. For multiple narrowband interferences case, a high-order cascaded adaptive interference suppression scheme is also presented. The simulation result demonstrates that the proposed narrowband interference suppression approach has excellent suppression effects to narrowband interferences in UWB systems, since a significant signal to noise ratio improvement is obtained. In addition, the proposed narrowband interference suppression algorithm is particularly fit for low-cost UWB wireless reception connected with Rake combining techniques.

Modified repetitive learning control with unidirectional control input for uncertain nonlinear systems

In order to asymptotically track the desired trajectory of nonlinear systems with unidirectional control input under various uncertainties, a modified saturated learning-based control law with adaptive notch filter (ANF) is presented in this paper. The proposed control law ensures the asymptotic convergence of the tracking error by utilizing a saturated function and a repetitive learning-based estimator, which allows the learning of the periodic dynamic behavior of the nonlinear system online to make compensations. Simultaneously, an ANF is integrated with the proposed control law to estimate the frequency of the periodic dynamics online. Differing from the existing methodologies in the literatures, the control law proposed in this paper only requires the unknown dynamics be bounded (the parameters, structure, and period of the unknown dynamics is not required to be known). Finally, applying the proposed control law to the electromagnetic suspension system, simulation, and experimental results are included to demonstrate the effectiveness of the proposed method.

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.

Levitation chassis dynamic analysis and robust position control for maglev vehicles under nonlinear periodic disturbance

In this paper, an experiment for decoupling the dynamic behavior of the levitation chassis of maglev vehicle with four electromagnetic suspension (EMS) modules is implemented, which validated that the stable suspension of maglev vehicle can be achieved by controlling individual EMS modules. Then, a dynamic model for single EMS module is established. A PD controller is designed to control the vertical position of the maglev vehicle. Simulations illustrate that the robustness of the controller is weak against the periodic disturbance. To improve the robustness of the controller, a nonlinear control law for disturbance rejection is applied by combining with a periodic disturbance estimator with an adaptive notch filter, which is capable of compensating exogenous nonlinear periodic disturbance. Different from using the existing control laws, the structure, parameters and period of the disturbance is not required. Moreover, the controller designed in this work satisfies the requirement of unidirectional force input. Simulation results are presented to demonstrate the excellent dynamic performance with the proposed robust controller.

Discrete derivative method for adaptive notch filter-based frequency estimators

This paper presents a new discrete derivative method for adaptive notch filter (ANF)-based frequency estimators. ANF-based frequency estimators are widely used for online frequency estimation because of their small computation requirements and simple structures. A discrete-time derivative is usually required for the estimators because they are implemented in the discrete-time domain. However, conventional discretization processes may cause problems in calculating the derivative of the adaptive filter state. For example, a derivative needs to have a phase of 90°, but finite difference methods produce phase responses that are less than 90° in high-frequency ranges. This phenomenon causes inaccurate frequency estimation results in high-frequency ranges. A bilinear transform method can prevent the phase problem, but it has oscillating transient responses, which deteriorate the convergence properties of the estimated frequency. A new discrete derivative method that modifies the bilinear transform is proposed. The proposed method does not produce the oscillating transient response in the steady state. Moreover, the phase responses of this method remain at 90° even in high-frequency ranges. Therefore, the frequency estimators that use the proposed derivative method can accurately estimate the frequencies of input signals in various frequency ranges.

Unbalance vibration suppression for AMBs system using adaptive notch filter

The unbalance of rotor levitated by active magnetic bearings (AMBs) will cause synchronous vibration which greatly degrade the performance at high speeds in the rotating machinery. To suppress the unbalance vibration without angular velocity information, a novel modified adaptive notch filter (ANF) with phase shift in the AMBs system is presented in this study. Firstly, a 4-degree-of-freedom (DOF) radial unbalanced AMB rotor system is described and analyzed, and the solution of rotor vibration displacement is compared with the experimental data to verify the preciseness of the dynamic model. Then the principle and structure of the proposed notch filter used for the frequency estimation and online identification of synchronous component are presented. As well, the convergence property of the algorithm is investigated. In addition, the stability analysis of the closed-loop AMB system with the proposed ANF is conducted. Simulation and experiments on an AMB driveline system demonstrate the effectiveness and the adaptive characteristics of the proposed ANF on the elimination of synchronous controlled current in a widely operating speed range.