Input Filter Research Articles

A New Approach to Input Filter Design for Regenerative Cascaded H-Bridge Drives

The diode-front-end (DFE) cascaded H-bridge (CHB) inverter has prevailed in the nonregenerative industry drive domain for high power medium voltage applications due to its modularity, scalability, and fault-tolerant capability. The regenerative version of the CHB drives is made possible by adding the extra active-front-end (AFE) rectifier in each power cell, such as a three-phase Pulse width modulation (PWM) rectifier. However, AFE introduces the switching harmonics which requires to be attenuated by designing a grid interfaced filter to comply with the harmonic standard IEEE 519-2014. High-order filters like <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCL</i> filters are not preferred due to complex inherent resonances in a multiparallel AFE system. A large number of capacitive components in the system rouse multiple resonances, which decreases system reliability and modularity. This article proposes an active filtering strategy based on the optimal asymmetric carrier-shifting method for regenerative CHB drives with only <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> filters. The required filter size is reduced significantly while complying with IEEE 519-2014 standard and thus improves the overall size, cost, and efficiency. The proposed filtering strategy is validated experimentally using a seven-level regenerative CHB drive.

Inter-patient arrhythmia identification method with RR-intervals and convolutional neural networks

Objective. The arrhythmia identification method based on the U-net has the potential for fast application. The RR-intervals have been proven to improve the performance of single-heartbeat identification methods. However, because both the heartbeats number and location in the input of the U-net are unfixed, the approach based on the U-net cannot use RR-intervals directly. To solve this problem, we proposed a novel method. The proposed method also can identify heartbeats of four classes, including non-ectopic (N), supraventricular ectopic beat (SVEB), ventricular ectopic beat (VEB), and fusion beat (F). Approach. Our method consists of the pre-processing and the two-stage identification framework. In the pre-processing part, we filtered input signals with a band-pass filter and created the auxiliary waveforms by RR-intervals. In the first stage of the framework, we designed a network to handle input signals and auxiliary waveforms. We proposed a masking operation to separate the input signal into two signals according to the result of the network. The first signal contains heartbeats of SVEB and VEB. The second signal includes heartbeats of N and F. The second stage consists of two networks and can further identify the heartbeats of SVEB, VEB, N, and F from these two signals. Main result. We validated our method on the MIT-BIH arrhythmia database with the inter-patient model. For classes N, SVEB, VEB, and F, our approach achieved F1 scores of 98.26, 68.61, 95.99, and 47.75, respectively. Significance. Our method not only can effectively utilize RR intervals but also can identify multiple arrhythmias.

Storytelling in the Inclusive L2 Classroom

This paper examines storytelling as a technology of teaching foreign languages with the help of fascinating stories in the inclusive environment. The relevance of developing inclusive education, i.e. integrating students with different individual characteristics (in particular, disabilities) into the learning process, is highlighted. In this regard, the concept of cognitive learning styles and Gardner’s theory of multiple intelligences are characterized as not quite suitable for the role of a general foundation of language teaching methodology in an inclusive classroom. Krashen’s Monitor Model, in its turn, is adopted as the theoretical basis of the modern approach to second language acquisition, emphasizing the importance of comprehensible input (received speech material) and emotional filter (psychological barrier) as key factors in the development of speech competence. In light of this, the advantages of a multisensory approach to language learning, and, in particular, the inclusive potential of using multisensory stories and creating students’ own stories with the support of a teacher (storybuilding), are clarified. Storytelling, thus, is considered by the authors of the article as a universal method for developing both receptive and productive speech skills in a foreign language for all kinds of students, including children with disabilities. The paper contains methodological recommendations regarding the implementation of storytelling technology in an inclusive classroom, including the conditions for effective assimilation of educational material by students with special educational needs. The principles of scaffolding (teacher support), mutual cooperation, clarity of instructions, sequence of material presentation, individualized information delivery forms, emotional involvement and integration are also explained. Based on the research literature on psychology, inclusive pedagogy and language education (Vygotsky, Rubinstein, Asher, Krashen), as well as some case studies featuring diverse students with varying disabilities, the authors argue for the need to gradually shift from skill-building to implicit teaching (and learning).

Optimal input filtering for networked iterative learning control systems with packet dropouts and channel noises in both sides

AbstractThis article is concerned with the convergence performance of wireless networked iterative learning control (ILC) systems with data dropouts and channel noises in both sensor‐to‐controller and controller‐to‐actuator channels. In order to improve the convergence performance of such ILC systems, an optimal input filter is developed at the actuator side to estimate controller updated input with the effect of these network uncertainties. Specifically, a filtering model is constructed only by using the learning process of P‐type controllers and the transmission process of both measured output data and updated input data. On the basis of this model and the orthogonality principle, the filter in the sense of linear minimum variance is designed at the actuator side so that the controller updated input could be estimated in iteration domain. The convergence performance of filtering error covariance matrix is analyzed theoretically. Moreover, because the filter design does not employ plant information, the tracking performance of any plant with P‐type learning controllers can be improved by driving with the filtered input. Simulation results show that the proposed filtering method is effective.

Three-Level Indirect Matrix Converter With Neutral-Point Potential Balance Scheme for Adjustable Speed Drives

To improve the performance and explore a new solution of adjustable speed drive systems, a T-type three-level indirect matrix converter (T3LIMC) topology and its modulation scheme are presented in this article. The presented topology is composed of an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> input filter, a current-source rectifier, and a T-type three-level inverter, where the split dc source voltage of the inverter is formed by two input line-line voltages and the neutral-point voltage. A multicarrier-based modulation scheme for the inverter and a specific zero-sequence voltage are also developed, and the desired neutral-point current of the inverter is constructed to compensate for the input currents. Consequently, the balanced neutral-point potential and symmetric sinusoidal input currents are achieved without additional control effort. In addition to advantages such as bidirectional power flow, sinusoidal input–output currents, controllable input power factor, no dc-link energy storage elements, and compact structure, the T3LIMC also improves the output waveform quality by generating the three-level output voltages. Meanwhile, the zero current switching (ZCS) operation of the rectifier helps to improve efficiency. Finally, the functionality and effectiveness of the presented topology and modulation scheme are verified by experimental results.

Bias-Compensated Sign Subband Adaptive Filter Algorithm With Individual Weighting Factors for Input Noise

To thoroughly exploit the decorrelation property of the traditional sign subband adaptive filter (SSAF), an individual weighting factors SSAF (IWF-SSAF) was presented. However, when the input of the adaptive filter is polluted by white Gaussian noise, the IWF-SSAF will produce estimation bias for unknown system identification. Thus, this brief proposes the bias-compensated IWF-SSAF (BC-IWF-SSAF) for resolving the above trouble. Especially, the unbiased criterion is applied to obtain compensation term for the conventional IWF-SSAF to alleviate the effect of noisy input. The proposed BC-IWF-SSAF both retains stability of impulse noise and decreases the estimated bias. The stable condition of the proposed BC-IWF-SSAF is achieved resorting to Price’s theorem with some reasonable assumptions and theorems. In addition, the complexity is given as well. Finally, simulations confirm the superiority of the proposed BC-IWF-SSAF algorithm.

A Variational Bayesian Deep Network with Data Self-Screening Layer for Massive Time-Series Data Forecasting.

Compared with mechanism-based modeling methods, data-driven modeling based on big data has become a popular research field in recent years because of its applicability. However, it is not always better to have more data when building a forecasting model in practical areas. Due to the noise and conflict, redundancy, and inconsistency of big time-series data, the forecasting accuracy may reduce on the contrary. This paper proposes a deep network by selecting and understanding data to improve performance. Firstly, a data self-screening layer (DSSL) with a maximal information distance coefficient (MIDC) is designed to filter input data with high correlation and low redundancy; then, a variational Bayesian gated recurrent unit (VBGRU) is used to improve the anti-noise ability and robustness of the model. Beijing’s air quality and meteorological data are conducted in a verification experiment of 24 h PM2.5 concentration forecasting, proving that the proposed model is superior to other models in accuracy.

Identification of Even-Order Harmonics Injected by Semiconverter into the AC Grid

In this study, the feedback effects of a three-phase half-controlled rectifier (also known as a semiconverter) to three-phase AC power grid was analyzed. Special attention was paid to the identification of harmonic order of the phase current. As a reference point for analysis, the mathematical model of an uncontrolled rectifier was used. The harmonic order of the phase current was identified by displaying the measurement results as well as using a mathematical model that is easily applicable, although this is unusual for harmonic analysis because it is based on time domain data. For this purpose, laboratory models of uncontrolled and half-controlled rectifiers were assembled. For both converters, the results obtained by practical laboratory measurements were compared to the mathematically obtained results, with the commutation in the mathematical model being ignored. The effects of commutation were analyzed in more detail for the laboratory model. For the semiconverter, the characteristic waveforms were studied for few different firing angles of the thyristor. Additionally, total power factor and total harmonic distortion of phase current were determined for all chosen firing angles. Finally, a comprehensive conclusion was drawn based on theoretically and practically obtained results on the appearance of even-order current harmonics, which should be taken into consideration when designing input filters and which contributes to power quality of the AC power grid.

Power decoupling control of single‐phase or three‐phase input high‐frequency single‐phase output matrix converters

AbstractThis study proposes a matrix converter (MC) control method capable of power decoupling (PD) for a single‐phase input isolated AC‐DC converter. The proposed converter can also be fed by a three‐phase source without any additional components. The PD circuit shares its capacitors with the input filters and its switches with the MC, and absorbs the source power ripple to supply a constant DC voltage for the load. Moreover, the MC control method achieves a sinusoidal source current, a high output frequency, and soft switching. Additionally, the feedback control to compensate for the DC output voltage error is applied. The proposed method is evaluated experimentally.

A Novel Multiphase Interleaved DC-DC Boost Converter with Reduced Input Current Ripple for Renewable Energy Application

This paper presents a new multiphase boost converter with improved input current ripple characteristics. The low input current ripple is important due to its effect on the converter’s efficiency and upstream dc bus noise level. It will further affect other devices connected to the same bus. Furthermore, for battery-connected systems such as renewable energy systems, the low current ripple increases the battery life. The method in this research uses split inductance and capacitance configuration as an input filter. The input filter helps compensating for the rippled converter topology, it reduces conduction-switching noise without affecting transient response, and it minimizes the physical size. Therefore, in this new topology, the use of smaller sized components directly influences the converter's size. Interleaved is used for improved heat distribution on the physical circuit board while retaining the benefits of a multiphase converter. Additionally, the low current ripple implies using smaller sized components that directly affect the size of the converter. A three-phase example of the proposed boost converter will be described, along with the derivation of its state space equations. Compared with the standard three-phase boost, the proposed converter can reduce the input current ripple and the output current ripple by 21% and 43%, respectively.

Speed-Sensorless Control of Induction Machines with LC Filter for Geothermal Electric Submersible Pumping Systems

A speed-sensorless state-feedback controller for induction machines (IMs) with LC filter is proposed. The speed and state estimation is based on a speed-adaptive observer, requiring only the measurement of the filter input currents. The motor currents are controlled by a state-feedback controller with prefilter and integral control action, in order to achieve fast and asymptotic set point tracking. Observer and controller gains are calculated offline using linear quadratic regulator (LQR) theory and updated online (gain-scheduling) in order to attain stability and improve controller performance in the whole operation range. Implementation aspects, such as discretization of the control system and reduction of computational effort, are taken into account as well. The proposed control scheme is validated by simulations and experimental results, even for critical operating conditions such as speed zero-crossings. It is shown that the overall control system performs very well under various load- and speed conditions; while its tuning remains simple which makes it attractive for industrial application such as geothermal electric submersible pumping (ESP) systems.

Vector Control and Modeling of Modular Multilevel High Voltage Converter for Rail Vehicle Traction

Rail transit plays an important role in the social and economic life of China and even all countries in the world, especially some populous countries or regions. The traction drive system of rail vehicle provides three-phase AC with adjustable voltage and frequency for the traction motor, controls the speed and torque of the traction motor, and then controls the operation of the vehicle. The modular multilevel converter has the advantages of low harmonic, good power quality of output waveform, high reliability, no input filtering and power compensation, and is suitable in the field of frequency conversion. In this work, the open-loop scalar control and vector closed-loop control of modular multi-level high-voltage inverter were adopted. It was found that driven by modular multi-level variable frequency vector control system, asynchronous motor not only has less harmonic content of voltage and current waveform, but also its speed regulation characteristics have been improved.

A New Design of a Miniature Microstrip Bandpass Filter for DCS Applications

This paper presents a new miniature Microstrip Bandpass Filter optimized and validated for DCS (Digital Cellular System) Band. The proposed filter is based on a Microstrip resonator. Each port has a step impedance feed line that can be used to adapt the filter's input impedance to the characteristic impedance Z0. The suggested filter is installed on a low-cost FR-4 substrate with a dielectric constant of 4.4, a thickness of 1.6 mm, a loss tangent tan (δ) = 0.025, and a metal thickness of t = 0.035 mm. It has a bandwidth of 1.68GHz to 2.05GHz. Two electromagnetic solvers are used to optimize and validate this filter. The whole dimensions of the final circuit are 33.6x40 mm2. This filter is suitable for mobile communication.

A High Step-Up Interleaved Current-Fed Resonant Converter for High-Voltage Applications

A current-fed LLC resonant converter is proposed for high-voltage and high-power applications. Here, a two-phase interleaved structure is used in the input stage under the continuous conduction mode (CCM) to effectively reduce the input current and output voltage ripple values and the input filter and the output capacitors volumes. Due to the expandable structure and high voltage gain, the proposed configuration is suitable for high voltage applications since low voltage stresses are applied across its components. In fact, voltage stresses across the power semiconductors, i.e., MOSFETs and output diodes, along with the output capacitors, are almost one-third of the output voltage in the implemented three-stage configuration of the proposed converter. Here, the switching frequency is chosen close to, but less than, the converter series resonant frequency to reduce its different components’ current stresses and perform soft-switching operation for all power devices under wide input voltage and output power variations. Therefore, conduction and switching losses, and EMI noises are effectively reduced. Consequently, efficiency is improved and high-frequency operation is possible, which reduces the volume of passive components to achieve high-power density. The given topology is thoroughly analyzed mathematically. Also, a 1 kW prototype converter has been implemented to validate the given simulations and analyses. Here, wide input voltage (100 V-200 V) and output power (100 W-1000 W) variations are applied, and an asymmetric pulse width modulation (APWM) technique is used at 143 kHz switching frequency to regulate the output voltage at 1 kV. The obtained maximum efficiency value is 95.3%.

General Tensor Least-Mean-Squares Filter for Multi-Channel Multi-Relational Signals

Least-mean-squares (LMS) algorithms constitute a prevalent approach to implement the linear adaptive filters whose coefficients can be updated sample by sample so as to track time-varying dynamics. As the memory and computational complexities required for the realization of LMS filters are very low, they have been widely adopted in many real-time signal processing applications. The input of any conventional LMS filter has to be a sequence of scalar samples (one-dimensional time series), whereas such assumption is too restrictive nowadays for multi-channel (high-dimensional) signals and multi-relational data in the rise of a big-data era. It is crucial to deal with high-dimensional data-arrays, a.k.a. tensors, to manifest the variety and complex interrelations of data. Owing to lack of a sufficient mathematical framework to govern relevant tensor operations, the general tensor LMS filter, whose input is allowed to be an arbitrary tensor, has never been established for realization to the best of our knowledge. In this work, we will dedicate a new mathematical framework for tensors to establish the general tensor least-mean-squares (TLMS) filter theory and propose two novel TLMS algorithms with update rules based on stochastic gradient-descent and Newton's methods, respectively. Furthermore, as we establish the tensor calculus theory, the performance evaluation on convergence-rate and misadjustment for our proposed TLMS filters can be conducted. Finally, the memory and computational complexities of the new TLMS algorithms are also studied in this paper.

Reconfigurable Non-Foster Elements and Squint-Free Beamforming Networks Using Active Transversal Filter-Based Negative Group Delay Circuit

A new type of reconfigurable negative group delay (NGD) circuits based on active transversal filter topology is introduced in this work. By incorporating varactors with the NGD circuit at the input and output ports of active transversal filter based on distributed amplifiers (DAs), one can notably enhance the tunability for both amplitude and phase responses, thereby enabling NGD characteristic synthesis with a wider reconfigurable range. In this article, the proposed reconfigurable NGD circuits are applied to create both tunable non-Foster elements and tunable squint-free beamforming networks, which are verified by experiment. Furthermore, a general <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$N$ </tex-math></inline-formula> -stage transfer function for the proposed reconfigurable NGD circuit is derived, in which a two-stage particular case is given as an illustrative proof-of-concept example. Based on the reconfigurable NGD circuits, a prototype of a tunable negative capacitor is fabricated and measured, of which the capacitance can be tuned from −1.0 to −4.0 pF over a bandwidth of 100 MHz at 1 GHz or around 10% relative bandwidth. In addition, such an NGD circuit is utilized to create a low-dispersion superluminal transmission line, which enables a reconfigurable series antenna feedline for squint-free beam steering. Experimental results show that the main beam of the NGD antenna array has a tuning range from −15° to 15° within a squint-free bandwidth of 100 MHz at 2 GHz or within a relative bandwidth of around 5%.

An Improved Least Stochastic Entropy Algorithm for Strong Noncircular Inputs and Noise

When the noise is second-order (SO) noncircular, the least stochastic entropy (LSE) algorithm can obtain a low steady-state misalignment compared to the complex-valued least mean-square (CLMS) algorithm. However, the convergence rate of LSE will decrease if the input of the adaptive filter is SO noncircular. This letter analyzes the cause of this problem and proposes an improved LSE (ILSE), which uses a combination strategy to accelerate its convergence rate. To predict its stochastic behavior, the performance of ILSE is analyzed. Simulation results are provided to verify the effectiveness of ILSE and the accuracy of the theoretical analysis.

A Filtering Method for Fast Convex Hull Construction

Computing the convex hull of a set of points is a fundamental issue in many fields, including geometric computing, computer graphics, and computer vision. This problem is computationally challenging, especially when the number of points is past the millions. In this paper, we propose a fast filtering technique that reduces the computational cost for computing a convex hull for a large set of points. The proposed method preprocesses the input set and filters all points inside a four-vertex polygon. The experimental results showed the proposed filtering approach achieved a speedup of up to 77 and 12 times faster than the standard Graham scan and Jarvis march algorithms, respectively.

Magnetically Coupled Single-Phase AC-AC Converter With Reduced Number of Passive Components

An AC-AC direct single-phase converter based on an impedance network is presented in this manuscript. It possesses all privileges of similar impedance source AC-AC converters such as buck-boost ability, maintaining or reversing the phase angle and sharing the same ground between input and output voltage. Furthermore, a magnetic coupling is exploited to provide high voltage gain by adjusting its turns ratio along with the duty cycle. A safe commutation strategy is implemented to avoid current and voltage spikes across switches needless to utilize snubber circuits. The presented converter offers continuous input current, and ac to ac conversion is done directly without using dc storage, making it appropriate for dynamic voltage restorer to compensate voltage sags and voltage swells. In addition, LC input and output filters are eliminated thanks to impedance network structure. In this regard, the presented topology offers good features in size and cost by reducing passive components compared to similar structures. Also, the comparative investigation shows that the proposed converter benefits from superior operational ranges among similar well-known topologies for the same conditions. Finally, theoretical analyses and operation modes of the proposed converter are discussed and testified by both simulation and experimental results.

Analysis of LCL Filter Topologies for DC-DC Isolated Cuk Converter at CCM Operation

In this study, the application and analysis of LCL filter topologies including an LCL, an LCL with damping, and an LCL trap filter used by a DC-DC isolated Ćuk converter operated at CCM are presented. The converter is designed for 50 W with 42 kHz switching frequency using a SiC MOSFET as a power switch. Although LCL filter topologies are commonly used with an inverter, their use in DC-DC converters has not been studied in detail. The main contribution of the paper is the application, design, and analysis of an LCL trap filter, which is not presented for a DC-DC converter in the literature, as an input filter of a DC-DC isolated Ćuk converter. For exact analysis of the effect of the filter, as a second main contribution of the paper, a state-space average mathematical model, small signal analysis of an isolated Ćuk converter for CCM operation, which was not presented before in the literature, is derived and its transfer function is obtained. In this paper, the practical design and transfer functions of LCL-based filter topologies are also presented. In order to analyze the effect of filter topologies by using linear methods including root locus and Bode graphs, the transfer function of the converter is cascaded with the transfer function of each filter separately, which is the third contribution of the paper because such analysis has not been presented in the literature. Furthermore, each cascaded transfer function and the transfer function of the converter are validated by step responses. All LCL filters, with an LC filter for comparison, are employed in the experimental setup. Owing to the applications, control characteristics and input current ripples are measured. In addition, the efficiencies of each different structure are determined. As a result of the analysis and measurements, the LCL trap filter gives better results in terms of efficiency (86%) and input current ripple (0.96 A peak). Moreover, the LCL with damping filter gives poorer control characteristics, but the maximum gain of the controller avoiding the instability of LCL with damping is 0.0855, which is higher than that of the others. Furthermore, it is shown that each LCL filter topology provides a 45% lower total inductor value compared to the LC filter.