Modulation Rectifier Research Articles

Stabilized Negative Resistance Emulating Control for Grid-Connected Inverter

Resistance emulating control is attractive due to the advantages of ease to use and less voltage sensor. However, it is only suitable for rectification mode. This letter presents a simple stabilized negative resistance emulating control for inverter mode, which overcomes the limitation of the conventional resistance emulating control. To stabilize the converter, a stabilizer based on negative inductance emulating is designed. Moreover, the unity power factor is realized by the steady-state inductance emulating technique. Since only the input current information is required, this control scheme is cost-effective and robust. Experimental results verify the effectiveness of the proposed method.

An Optimization Method of Dual-Side LCC Compensation Networks Simultaneously Considering Output Power and Transmission Efficiency in Two Directions for BWPT Systems

This article presents an optimization method of dual-side <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensation networks for bidirectional wireless power transfer systems, which aims to simultaneously realize the rated forward and reverse output power directly through compensation network designing. In addition, due to that the optimization results of compensation networks are close to the values that meet the condition of the maximum transmission efficiency, good system efficiency in the two directions can be simultaneously obtained under the rated condition. Firstly, an equivalent circuit of bidirectional power converter (BPC) working in rectification mode is established, which includes the parasitic and external parallel capacitance of metal oxide semiconductor (MOS) devices. Also, its equivalent impedance is calculated. Then, considering the reactance part of the BPC equivalent impedance, the optimization method of the dual-side <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LCC</i> compensation networks is analyzed. Finally, a 3.3 kW BWPT prototype is developed to verify the proposed method. The simulation and experiment results showed that the effect of the parasitic and parallel capacitance of MOS devices, on the reactance part of BPC equivalent impedance is more obvious; the proposed optimization method can simultaneously realize the rated forward and reverse output power, and both forward and reverse transmission efficiency are greater than 94% under the rated condition.

The magnetic field self-display system of coupler for wireless power transfer systems based on magnetic structure factor

The magnetic field surrounding wireless power transfer (WPT) systems is difficult for the general public to discern in practice. To address this problem, a system that only measures the current in the coils for transferring and receiving to get the coupler’s magnetic field strength at a specific geographic location in space is proposed. The system includes a current transformer, inductive power-harvesting device, rectifier module, voltage regulation module, microprocessor, AD module, and display module. Due to the fixed mechanical structure and position of the coupler when working, the calculation model of the magnetic field of the coupler is established, and the magnetic structure factor based on the mechanical structure of the coupler is defined. The system can obtain power and operate based on the inductive power harvesting principle without damaging the WPT system structure. It also can realize the convenient display of the magnetic field and avoid the dependence on professional instruments when measuring the magnetic field of the coupler. In addition, it is easy to implement in practice.

Pavement crack detection from CCD images with a locally enhanced transformer network

• A novel Transformer-based deep neural network was proposed for pavement crack detection. • Transformer modules extracted global contextual information for long-range dependency modeling. • A local enhancement module was designed to compensate for fine-grained local features. • A manually annotated pavement crack dataset was built for high-resolution CCD image-based pavement crack detection. Precisely identifying pavement cracks from charge-coupled devices (CCDs) captured high-resolution images faces many challenges. Even though convolutional neural networks (CNNs) have achieved impressive performance in this task, the stacked convolutional layers fail to extract long-range contextual features and impose high computational costs. Therefore, we propose a locally enhanced Transformer network (LETNet) to completely and efficiently detect pavement cracks. In the LETNet, Transformer is employed to model long-range dependencies. By designing a convolution stem and a local enhancement module, both low-level and high-level local features can be compensated. To take advantage of these rich features, a skip connection strategy and an efficient upsampling module is built to restore detailed information. In addition, a defect rectification module is further developed to reinforce the network for hard sample recognition. The quantitative comparison demonstrates that the proposed LETNet outperformed four advanced deep learning-based models with respect to both efficiency and effectiveness. Specifically, the average precision, recall, ODS, IoU, and frame per second (FPS) of the LETNet on three testing datasets are approximately 93.04%, 92.85%, 92.94%, 94.07%, and 30.80FPS, respectively. We also built a comprehensive pavement crack dataset containing 156 high-resolution manually annotated CCD images and made it publicly available on Zenodo.

Multiple open-circuit fault diagnosis of three-phase rectifier based on current data reconstruction

ABSTRACT A novel and real-time fault diagnosis method based on current data reconstruction for rectifiers is proposed in this article. The symmetry of a 3-phase pulse-width modulation rectifier’s topology can be used for fault diagnosis. The symmetry is broken when open-circuit faults happen, a similarity measurement algorithm based on current data reconstruction is used for fault detection. Fault characteristics for current lists and multi-scale entropy are proposed to locate different kinds of faults. The proposed diagnostic method doesn’t need additional hardware devices and costs low. It is convenient to be embedded in an existing control system as a subprogram without significant adjustments. The experimental results show the effectiveness of the proposed diagnostic method for both single and multiple open-circuit faults.

Modelling and Control of Single-Phase Bidirectional AC/DC Converter Used in Microgrid Energy Systems

In this study, bidirectional single-phase PWM AC/DC converter that is used in microgrid systems at connection point to the grid, is modelled and controlled. PWM signals of the converter is generated with hysteresis current control technique. The mathematical model is developed in Matlab/Simulink. The converter with 5 kW active power capability is examined in rectifier and inverter mode for steady-state and transient response. Two operation modes of the converter is existed by changing power of the DC load and source. The converter transfers the energy from grid to DC bus in rectifier mode while the energy in the DC bus is transferred to grid in inverter mode. The grid current THD% values meet IEEE 1547 and IEEE 519 standards in both modes with 1.52%. The reactive power support of the converter with phase angle control of the grid current is presented. In both modes, reactive power of 500-900 VAr are provided. The obtained results show the availability of the modelling and control of the converter for active and reactive power generating.

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.

Switching Transition Analysis and Optimization for Bidirectional CLLC Resonant DC Transformer

The demand for isolated bidirectional dc transformer (DCX) is driven by the fast development of energy storage system, data center power supply and transportation electrification. Due to zero voltage switching (ZVS) and small rms current, the open-loop CLLC resonant converter operating at the resonant frequency is considered a promising candidate for DCX with a constant voltage transfer ratio. To solve unsmooth bidirectional power flow and current distortion in traditional CLLC-DCX with synchronization rectification (SR) modulation, a dual-active-synchronization (DAS) modulation is adopted with identical driving signals on both sides. Firstly, the switching transition of this modulation is fully analyzed with the consideration of large device output capacitances. After comparison of different transitions, a so-called Sync-ZVS transition is found more desirable with ZVS, no deadtime conduction loss, and load-independent voltage gain. In order to achieve this switching transition, an Axis and Center Symmetric (ACS) method is proposed. Based on this method, an overall design procedure of CLLC-DCX with DAS modulation is also proposed. Finally, Sync-ZVS transition and the proposed ACS method are both verified by three 18 kW 500 kHz prototypes with a 98.8% peak efficiency. This article is accompanied by one video demonstrating the load changing test.

Low-Frequency Oscillation Analysis in Train-Traction Power Supply System Using an SISO Voltage Loop Model

Low-frequency oscillation (LFO) in the train-grid coupling system severely endangers the stability and safety of railway operation. It is well known that this phenomenon is caused by impedance mismatch among the trains and the traction power supply system (TPSS). A novel voltage loop model of the single-phase pulsewidth modulation rectifier is proposed in this article. Unlike the commonly adopted multi-input multi-output (MIMO) <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> impedance model in the literature, this is a single-input single-output (SISO) model that enjoys some advantages, such as easier calculation of the system poles and quantitative analysis of the stability margin. The most attractive character of this model in comparison to the MIMO one is perhaps the decoupling of the controller and the voltage loop. This paves the way toward the analytical design of the dc-link voltage controller (DVC), whereas the impedance model is mainly useful for analysis. Furthermore, the maximum amount of trains allowed for keeping stability is derived from the steady-state equation. Robust stability margin (RSM) and sensitivity analysis are adopted to quantitatively investigate the influence of the control parameters and the circuit element parameters. LFO is guaranteed to be eliminated permanently by adjusting the controller parameters.

Enhancing Doubly Fed Induction Generator Low-Voltage Ride-through Capability Using Dynamic Voltage Restorer with Adaptive Noise Cancellation Technique

Some of the major challenges facing micro-grids (MGs) during their connection with the utility grid are maintaining power system stability and reliability. One term that is frequently discussed in literature is the low-voltage ride-through (LVRT) capability, as it is required by the utility grid to maintain its proper operation and system stability. Furthermore, due to their inherent advantages, doubly fed induction generators (DFIGs) have been widely installed on many wind farms. However, grid voltage dips and distortion have a negative impact on the operation of the DFIG. A dynamic voltage restorer (DVR) is a commonly used device that can enhance the LVRT capability of DFIG compared to shunt capacitors and static synchronous compensator (STATCOM). DVR implements a series compensation during fault conditions by injecting the proper voltage at the point of common coupling (PCC) in order to preserve stable terminal voltage. In this paper, we propose a DVR control method based on the adaptive noise cancelation (ANC) technique to compensate for both voltage variation and harmonic mitigation at DFIG terminals. Additionally, we propose an online control of the DC side voltage of the DVR using pulse width modulation (PWM) rectifier to reduce both the size of the storage element and the solid-state switches of the DVR, aiming to reduce its overall cost. A thorough analysis of the operation and response of the proposed DVR is performed using MATLAB/SIMULINK under different operating conditions of the grid. The simulation results verify the superiority and robustness of the proposed technique to enhance the LVRT capability of the DFIG during system transients and faults.

IPWM Based IBMSC DC-AC Converter Using Solar Power for Wide Voltage Conversion System Convertisseur DC-AC IBMSC basé sur l’IPWM et utilisant l’énergie solaire pour un système de conversion à large tension

This article proposes isolated bidirectional micro dc-ac single phase controlled (IBMSC) converter based on in-phase–voltage pulsewidth modulation (IPWM). This resonant IPWM converter, ratio of voltage conversion can be controlled from 0 to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\infty $</tex-math> </inline-formula> . So, this converter is highly referred for huge range voltage conversion. However, voltage conversion ratio determines power transfer direction and duty ratio. Power flow direction and duty cycle value can be varying smoothly, so it is suitable for dc-ac bidirectional power conversion application. Inverter mode and also rectifier mode are possible from bidirectional operation, which is controlled by a unified current controller. The proposed solution can achieve smooth switching grid operation with high efficiency. Working principle, design procedure, control strategy, and characteristics of the proposed converter are implemented with a prototype model of power rating 500 W with a voltage range of 20–50 V to test the ability of withstanding. Performance, feasibility, and effectiveness of the proposed converter are tested with this hardware test-bench model.

Feature Split–Merge–Enhancement Network for Remote Sensing Object Detection

Recently, multicategory object detection in high-resolution remote sensing images is still a challenge. First, objects with significant scale differences exist in one scene simultaneously, so it is generally difficult for the detectors to balance the detection performance of large and small objects. Second, because of the complex background and the objects&#x2019; densely distributed characteristics in the remote sensing images, the extracted features usually have noise and blurred boundaries, which interfere with the detection performance of the object detectors. With this observation, we propose an end-to-end scale-aware network called feature split&#x2013;merge&#x2013;enhancement network (SME-Net) for remote sensing object detection, composed of the feature split-and-merge (FSM) module, the offset-error rectification (OER) module, and the object saliency enhancement (OSE) strategy. FSM eliminates salient information of large objects to highlight the features of small objects in the shallow feature maps. It also transmits the effective detailed features of large objects to the deep feature maps, alleviating feature confusion between multiscale objects. OER corrects the inconsistency of the features spatial layout among the multilayer feature maps by the proposed offset loss, so as to achieve supervised elimination and transmission in FSM. OSE enhances the features of interests and suppresses the background information by the proposed membership function, thus preventing false detection and missed detection caused by noise and blurred boundaries. The effectiveness of the proposed algorithm has been verified on multiple datasets. Our code is available at: <uri>https://github.com/Momuli/SMENet.git</uri>

Slidable Button-shaped Rectifier Module with LED on Conductive Yarn for Antenna Matching Powered by Microwaves

Slidable Button-shaped Rectifier Module with LED on Conductive Yarn for Antenna Matching Powered by Microwaves

A Multifunctional Device Based on Graphene/Silicon Heterojunction

Heterojunction devices based on two-dimensional materials have been widely studied in the fields of electronics and optoelectronics. As the complexity of the chip system increases, the ability to realize multi-function in a single device is increasingly in demand. Here, we propose a multifunctional device based on graphene/silicon heterojunction, which can operate in photodetection mode or tunable rectifier mode. The heterojunction barrier is tunable by the external electric field. The photodetection range covers ultraviolet to visible, and the responsivity can reach 51 A/W and 495 A/W at 266 nm and 532 nm while keeping the off-state current at a low level of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-8</sup> A. With the control of the external electric field, the device can also function as a tunable rectifier to achieve three states: positive-pass, off, and negative-pass, which can be applied in signal processing and logic circuit. The multifunctional integrated device has potential in future optoelectronic logic applications while reducing the cost and the device footprint.

A New Technique for Online Open Switch Fault Detection and Location in Single-phase Pulse Width Modulation Rectifier

A New Technique for Online Open Switch Fault Detection and Location in Single-phase Pulse Width Modulation Rectifier

Elimination of Circulating Current in a Parallel PWM Rectifier Using an Interface Circuit

Parallel pulsewidth modulation rectifiers are a good solution for high-power ac–dc applications, which enhance quality and reliability. However, the main and inevitable shortcoming of parallel structures is a generation of circulating current. Various methods are proposed to reduce or eliminate circulating current, most of which tend to change or limit the switching pattern of parallel converters. This article presents an interfacing circuit with low rating elements, which eliminates the circulating current without any limitation for the switching pattern of parallel converters. Therefore, voltage and current waveforms are in high quality. Moreover, unlike previous methods that had complex control and high mathematical computations, the presented method has simple control. Therefore, multiple modules can be implemented in a modular fashion with a fast dynamic response. Simulation and Laboratory results are presented to validate the analysis.

PETR: Rethinking the Capability of Transformer-Based Language Model in Scene Text Recognition.

The exploration of linguistic information promotes the development of scene text recognition task. Benefiting from the significance in parallel reasoning and global relationship capture, transformer-based language model (TLM) has achieved dominant performance recently. As a decoupled structure from the recognition process, we argue that TLM's capability is limited by the input low-quality visual prediction. To be specific: 1) The visual prediction with low character-wise accuracy increases the correction burden of TLM. 2) The inconsistent word length between visual prediction and original image provides a wrong language modeling guidance in TLM. In this paper, we propose a Progressive scEne Text Recognizer (PETR) to improve the capability of transformer-based language model by handling above two problems. Firstly, a Destruction Learning Module (DLM) is proposed to consider the linguistic information in the visual context. DLM introduces the recognition of destructed images with disordered patches in the training stage. Through guiding the vision model to restore patch orders and make word-level prediction on the destructed images, visual prediction with high character-wise accuracy is obtained by exploring inner relationship between the local visual patches. Secondly, a new Language Rectification Module (LRM) is proposed to optimize the word length for language guidance rectification. Through progressively implementing LRM in different language modeling steps, a novel progressive rectification network is constructed to handle some extremely challenging cases (e.g. distortion, occlusion, etc.). By utilizing DLM and LRM, PETR enhances the capability of transformer-based language model from a more general aspect, that is, focusing on the reduction of correction burden and rectification of language modeling guidance. Compared with parallel transformer-based methods, PETR obtains 1.0% and 0.8% improvement on regular and irregular datasets respectively while introducing only 1.7M additional parameters. The extensive experiments on both English and Chinese benchmarks demonstrate that PETR achieves the state-of-the-art results.

Robust predictive current control of PWM rectifiers with LCL filters under unbalanced and distorted network conditions

Pulse-width modulation (PWM) rectifiers with LCL filters can achieve better filtering and have lower total inductance than its counterpart of L filters. However, the control complexity is also increased due to the higher system order. Furthermore, the performance may deteriorate significantly when the inductance used in the controller deviates from its actual value due to saturation, temperature, and so on. This paper proposes a robust predictive current control (RPCC) scheme based on the ultra-local model for LCL-filtered PWM rectifiers. Excluding the converter voltage related term, the other part of the system F including the disturbance caused by parameter mismatches and other dynamic process, can be estimated using differential algebra (DA) or an extended state observer (ESO). After obtaining F, the reference voltage vector can be calculated based on the principle of deadbeat current control. The proposed RPCC is extended to an unbalanced and distorted grid by modifying the grid current reference; thus, the three-phase grid currents are balanced and sinusoidal. The proposed RPCC based on DA and ESO is compared to the conventional model-based predictive current control (MPCC), and the experimental results confirm its robustness and effectiveness under mismatched parameters and network disturbances.

Research on a high power density mechanical-electrical-hydraulic regenerative suspension system for high-speed tracked vehicles

High power density energy regeneration is one of the effective solutions to solve the contradiction between improving the damping performance and energy consumption of active suspension. The hydraulic commutator is used to realize hydraulic rectification and hydraulic variable speed/pump/motor with few teeth difference gear pairs is used to match the speed, combined with permanent magnet motor power generation and power supply to put forward kilowatt level high power density mechanical-electrical-hydraulic regenerative suspension system for high-speed tracked vehicles. The mathematical model and fluid-solid-thermo-magnetic multiphysics coupling model are built to analyze the damping performance and regenerative characteristics of the system under passive and semi-active working conditions. The simulation results show that the damping force of the system increases with the increase of the road excitation amplitude and the semi-active control can be realized by adjusting the duty cycle with the PWM control rectifier module. The high power density mechanical-electrical-hydraulic regenerative suspension system can realize kilowatt level energy regeneration, and the regenerative efficiency is more than 50% under low-frequency excitation. The temperature rise of the system is low during operation, which is helpful to improve the reliability and service life.

Performance of Neutral Point Clamped Five Level Inverter Using Space Vector Modulation Control Fed by DPC-VF-SVM Rectifier

The purpose of this paper is to develop a control and regulation method for the input DC voltage of a five level neutral point clamping (NPC) inverter feeding a induction motor. In this context, the authors propose in the first part, the control strategy of three-phase pulse width modulation rectifier, they propose the virtual flux-based direct control (DPC_VF) with vector modulation (SVM), this method is applied for the enhancement of network power quality by compensation of harmonic currents produced by an non linear load, and good regulation of DC-bus voltage. The second part of the paper is dedicated to the presentation of the model of the three phase, five-level NPC voltage source inverter with its space vector modulation (SVM) control method. The performance of the proposed strategy in terms of out-put voltage and THD has studied successfully and shown using MATLAB/Simulink.