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Accurate and timely fault diagnosis of the rotating rectifier for a wound-rotor synchronous starter/generator is of great importance to improve system reliability. In the generation mode of the system, there is one idle stator winding of the main exciter. The terminal voltage characteristic of the idle stator winding is analyzed, and a novel fault diagnosis method for the rotating rectifier in the generation mode of the system is proposed. In this method, two feature voltages, namely, the maximum peak voltage and any other peak voltage of the idle stator winding terminal voltage are extracted through voltage sequence reconstruction to calculate the feature ratio for fault detection. The corresponding rotor position obtained by an inherent position sensor where the maximum peak voltage occurs is collected to determine the faulty diode location. The experimental results verify the feasibility and effectiveness of the proposed fault diagnosis method.

To utilize the full potential of the direct matrix converter (DMC) and improve the output waveform quality, a three-level output strategy for conventional 3 × N ( N ≥3) DMCs is presented, where three-level output voltages are achieved without any changes in the topology. In this developed strategy, the DMC is treated as a two-stage converter that consists of a fictitious rectifier and a neutral-point clamped (NPC) three-level inverter. By applying a phase-shifted carrier modulation strategy to the rectifier and a modified carrier-based double-signal pulsewidth modulation strategy to the NPC inverter, sinusoidal input and output, reduced switching losses, and controllable input power factors are achieved in conventional 3 × N DMCs. The developed three-level output strategy improves output waveform quality while sacrificing input performance to some extent. Finally, the effectiveness of the developed strategy is verified by both simulations and experimental results.

In the mm-wave frequency band, the rectifier’s sensitivity is the bottleneck of a wireless-powered IoT transponder’s distance. At a meter’s distance, the received power is weak, and transistors in a front end of a wireless power receiver operate in the weak inversion region. This article presents a mathematical analysis of the mm-wave multi-stage rectifier in the low-power region. A design methodology of a 57–64-GHz fully integrated eight-stage rectifier with a bulk-drain connection in 40-nm CMOS technology is presented. Parasitic effects on a multi-stage rectifier are analyzed. Based on the analysis, an intrinsic threshold voltage modulation is applied to improve the sensitivity. A tree-type power splitter is also proposed for the RF power signal’s phase balance. With this method, the RF signal arrives at each stage with an equal phase, and its suppression at the output is improved by 16 dB. This mm-wave rectifier achieves − 7.1-dBm input sensitivity at 57 GHz with 1-V dc output voltage. The overall sensitivity from 57 to 64 GHz is better than − 4.5 dBm. Compared to other mm-wave silicon-based rectifier state of the arts, the proposed mm-wave rectifier achieves better sensitivity while maintaining a compact size.

In this paper, an innovated buried layer rectifier (BLR) breakdown voltage (BV) instability has been tested and analyzed. Under the reverse current stress (RCS) condition, the BV read-out profiles show walk-in and walk-out phenomena. Based on the experimental results and surface traps theory, a sort of time dependent degraded simulation is developed by TCAD tools, which is considered with hydrogen depassivation and diffusion process. In order to explore the inner mechanism, the dynamic electric parameters are analyzed during the degraded period. Due to the hole interface traps, the termination Si-SiO2 surface leakage current is deteriorated and the depletion boundary is shrunk, which reveals the BV values instability. Thus, the proposed physical model could clearly explain the whole process of degradation, while it fits BV and junction temperature curves to the experimental results identically. Furthermore, the investigated mechanism will be helpful to future device design and failure situations analysis.

This paper presents general modeling approaches to achieve accurate real-time simulation of high switching frequency converters. The proposed methods are based on the direct mapped method (DMM) and make use of decoupling techniques when appropriate. The DMM links state variables to diode statuses and provides an exact and noniterative solution to network equations. An electric vehicle battery charger (EVBC) test case comprised of a full bridge rectifier, an interleaved boost, and a three-phase LLC is used to demonstrate the high accuracy achieved by the proposed methods compared to a conventional approach. FPGA implementations are proposed and shown to achieve from 75 ns to 175ns real-time simulation time-steps for this test case circuit, allowing its accurate simulation while switched at 200 kHz. To further validate the effectiveness of the FPGA-based simulator, a resonant boost converter is also implemented and simulated in real-time.

This paper proposes a primary-side linear control strategy to realize the constant current (CC)/voltage (CV) charging for the wireless power transfer (WPT) system, based on the LCC-N circuit. Different from the conventional compensation topology used in control strategies, this paper combines magnetic integration structure on the primary side and non-compensation topology on the secondary side. Firstly, the LCC-N magnetic integration and non-compensation topology is introduced. An improved parameters identification method considering the non-pure resistive input impedance characteristics of the rectifier is proposed to identify the current, voltage and equivalent resistance of the load, based on the LCC-N topology. In the process of identification, the relationship between the input impedance of the rectifier and the load is needless. Then, according to the LCC-N output characteristics and identified load parameters, the relationship between the input voltage and load current and voltage is simplified to linear through the linear superposition of fundamental wave and third harmonic. A linear control strategy on the primary side is proposed to achieve CC/CV output. Finally, a 1 kW WPT prototype is built. The experimental results show that the maximum error of the output current and voltage are 1.8% and 1.2% during the CC and CV charging, respectively.

This paper presents the design of highly efficient rectifiers that can operate at WiFi frequencies (2.45 GHz and 5.8 GHz) and match low input power. The designed dual-band rectifiers use multi-stage dickson voltage multipliers (DVM) (from 1 to 6 stages), and the main idea of this paper is to find the number of stages that offers the best performance and that can be used by applications that operate within the same constraints (operating frequencies, input power). The efficiency and the output voltage (Vout) are the parameters studied to analyze the designed rectifiers. The results showed that as the number of DVM stages increased, the efficiency curves for both frequencies shifted to the higher input power range, even when using the same diode (SMS7630) and the same load (5 KΩ). We concluded that the rectifier with 1-stage DVM is the most suitable to be used for low input power at the selected frequencies since it provides an efficiency of 57.734% at 0 dBm for 2.45 GHz and 36.225% at 1 dBm of input power for 5.8 GHz.

Purpose. Increasing the operational indicators of suburban transportation on railways electrified by alternating current due to the modernization of traction static converters of ER9M electric trains. Methodology. The methodological basis of the study is the general theoretical provisions and principles of the system approach of theoretical electrical engineering, the theory of power converters. The main principles of construction of traction static converters of electric rolling stock of railways are used. Findings. The analysis of the basic rectification schemes of alternating current electric trains was performed. As an alternative scheme, it is proposed to introduce a controlled rectification scheme based on a four-zone rectification scheme, which is similar to electric locomotives, which allows using most of the known advantages of non-contact traction electric drive control systems. Some energy figures are calculated for the fully controlled and semi-controlled circuit. As a result of the comparison, the modernization option based on a semi-controlled rectification scheme was selected. The required values of starting power of the transformer and power factors for schemes with uncontrolled, fully controlled and semi-controlled rectifiers are determined. A selection of modern semiconductor elements is offered for the configuration of converters. It was shown that in the case of modernization of the rectifier scheme, there is no need for significant capital investments due to the preservation of the main traction transformer and traction motors of the electric train. Practical value. The obtained results can be used by enterprises that carry out major repairs of alternating current electric trains., Мета. Підвищення експлуатаційних показників приміських перевезень на залізницях, що електрифіковано змінним струмом за рахунок модернізації тягових статичних перетворювачів електропоїздів ЭР9М. Методи. Методологічною основою дослідження є загальні теоретичні положення і принципи системного підходу теоретичної електротехніки, теорії силових перетворювачів. Використано основні принципи побудови тягових статичних перетворювачів електрорухомого складу залізниць. Результати. Виконано аналіз базових схем випрямлення електропоїздів змінного струму. У якості альтернативної схеми запропоновано впровадження керованої схеми випрямлення на базі чотирьох зонної схеми випрямлення, яка є аналогічною для електровозів, що дозволяє використати більшість з відомих переваг безконтактних систем управління тяговим електроприводом. Обчислені деякі енергетичні показники для схеми з повним керуванням та пів керованої. У результаті порівняння вибрано варіант модернізації на основі пів керованої схеми випрямлення. Визначені необхідні значення пускової потужності трансформатора та коефіцієнти потужності для схем з некерованим, повністю керованим та пів керованим випрямлячами. Пропонується вибір сучасних напівпровідникових елементів для комплектації перетворювачів. Показано, що у разі модернізації схеми випрямляча відсутня необхідність значних капітальних вкладень завдяки збереженню основного тягового трансформатора та тягових двигунів електропоїзда. Практична значимість. Одержані результати можуть бути використані підприємствами, які виконують капітальний ремонт електропоїздів змінного струму.

The need for constant supply of electricity to protect steel structures brings about the use of solar cells. This research work involves the cathodic protection of underground mild steel pipes by impressed current using solar cells as rectifier. The pipes were buried at two separate sites; X and Y. Site X for the control experiment and Y for the main experiment. The Impressed Current cathodic Protection (ICCP) was applied to the pipes on site Y and the pipes on site X buried without any protection for a period of 40 days. The Pipe to Soil Potentials (PSP) was measured for the pipes on the two sites using multimeter. The pipe to soil potentials measured for the pipes on site Y were within the range recommended for protection (

The battery pack of an electric car is a significant energy source that may be used for a variety of things, including charging additional electric vehicles and connecting them to the grid, homes, and homes. The charging modes in this work can be changed to your preference. This essay discusses how electric vehicles charge on-board and how to comprehend the charging process from the vehicle to the home. However, li-ion batteries need safeguards to prevent overcharging or undercharging, which can shorten their useful lives and decrease their efficiency. As the world moves towards a more sustainable transportation system, electric vehicles (EVs) are becoming increasingly popular. However, to support the widespread adoption of EVs, an extensive charging infrastructure is necessary. The shift to a more environmentally friendly and sustainable transportation system depends heavily on electric car chargers. This essay examines developments in EV charging technology, problems with EV charging infrastructure, and future possibilities for EV chargers. So, by including SMPS (Switching Mode Power Supply) we can use it as a converter as well as current controlling device. Additionally, cooling vents in front and inside of the hardware as well are also installed.

Single-loop current sensorless control allows for abolishing of the instantaneous current measurement in the control system using only a single control loop with voltage feedback to stabilise the DC-bus voltage. This approach eliminates current sensors in the control circuit, benefiting from saving space on the printed circuit board and minimising power dissipation in the current measurement circuitry. This paper focuses on the single-loop current sensorless control applied to bidirectional three-phase four-wire three-level NPC MLC by simulation analysis and demonstrates the performance of the proposed current control algorithm in the rectifier and inverter modes and the step response with power direction change and grid-voltage change. In capacitor voltage balancing, an additional controller is applied, which is capable of compensating for the voltage asymmetry caused by adding a 2.5 kOhm resistor in parallel to one of the DC-bus capacitors. Our results demonstrate good performance of the proposed control method both in the inverter and rectifier modes, showing stable current shape in the low power and full power modes with acceptable harmonics content, meeting the requirements of the IEC 61000-3-2 standard for Class A devices. The analysis showed that the proposed control approach is suitable for industrial application.

This paper presents a new rectifier design for radio frequency (RF) energy harvesting by adopting a particular circuit topology to achieve two objectives at the same time. First, work with modulated input signal sources instead of only continuous waveform (CW) signals. Second, operate with a wide input power range using the Wilkinson power divider (WPD) and two different rectifier diodes (HSMS2852 and SMS7630) instead of using active components. According to the comparison with dual-band rectifiers presented in the literature, the designed rectifier is a high-efficiency rectifier for wide RF power input ranges. A peak of 67.041% and 49.089% was reached for 2.45 and 5.8 GHz, respectively, for CW as the input signal. An efficiency of 72.325% and 45.935% is obtained with a 16 QAM modulated input signal for the operating frequencies, respectively, 69.979% and 54.579% for 8PSK. The results obtained demonstrate that energy recovery systems can use modulated signals. Therefore, the use of a modulated signal over a CW signal may have additional benefits.

This paper proposes digitally controlled power management circuit (PMC) for vibration energy harvesting in vehicle suspension system. The PMC is tested with a mechanical motion rectifier based electromagnetic energy harvester that converts from bi-directional vibration to unidirectional rotation, with improved energy harvesting performance and efficiency. Topology of one-stage DC-DC converter is adapted, and it is digitally controlled while considering the uncertainty of vibration sources. In order to efficiently transfer the harvested power to the electrical load, the algorithm of digital controller is designed to have four operation modes, which are impedance matching mode, voltage regulation mode, generator protection mode, and low power mode, for increasing the PMC efficiency while reducing the power consumption of controller. Experimental results show that proposed circuit can successfully operate and switch between the four operation modes. In the evaluation of PMC performance with 2mm and 2Hz excitation, the efficiency of proposed one-stage power converter is 86%. The total power consumption of controller in active mode and low power mode are 109 mW and 2.52 mW respectively while harvesting about 3W vibration energy.

Following the continuous development of wide bandgap (WBG) devices and multilevel converter technology, medium voltage (MV) active front ends (AFEs) are becoming promising in future high-power-density and high-power applications. However, the cost issue is one of the major drawbacks, which stops the WBG devices from being widely applied in high-power areas. This paper proposes a silicon carbide (SiC) and silicon (Si) hybrid five-level unidirectional rectifier. It requires only four SiC MOSFETs with relatively low blocking voltage and four Si diodes. Meanwhile, by adding snubber capacitors, all the Si devices are with low-speed switching, and the voltage stresses of fast SiC MOSFETs are minimized. In this paper, operational analysis and carrier-based phase-disposition PWM scheme for this circuit are discussed in detail. The capacitor voltage balancing and unity power factor are both realized. Simulation and scaled-down experimental results are demonstrated to verify the proposed rectifier. Furthermore, the comparison of the hybrid five-level rectifiers is given to show the advantages of the proposed rectifier in terms of voltage stress, efficiency, and cost.

With the rapid and extensive development of wireless communication and low power electronics, electromagnetic wireless power harvesting (WPH) draws more and more attention. As the core component for RF-to-DC power conversion, its characteristics determine the performance of the overall system. To obtain as much DC energy as possible, ambient electromagnetic energy with various frequencies should be efficiently rectified. Therefore, its important to widen the operating bandwidth of the rectifier. According to the theoretical analysis of the Schottky diode, it can be found that if the harmonic components generated by the diode can be fed back through a specific approach for rectifying, the bandwidth of the rectifier will be effectively improved. Therefore, a broadband rectifier has been proposed based on the previous principle. For validation, a wideband rectifier based on Schottky diode SMS7630 had been designed, fabricated and measured. When the input power level is 0 dBm, the conversion efficiency of the implemented rectifier is larger than 40% from 0.4 GHz to 2.6 GHz within a relative bandwidth of 146.67%, exhibiting an ultra-wide bandwidth compared with existing state-of-the-art configurations.

based on the characteristics that the magnitude of active-current vector in the rectifier stage is zero when the zero-voltage vector is used in the inverter stage, a novel Discontinuous Pulse Width Modulation (DPWM) strategy for the indirect matrix converter is proposed in this paper to reduce the common-mode voltage (CMV). In this DPWM strategy, the reference current vector in the rectifier stage is synthesized by two adjacent active-current vectors, and the reference voltage vector in the inverter stage is synthesized by two adjacent active-voltage vectors and one zero-voltage vector. When the inverter stage utilizes one zero-voltage vector, the active-current vector with zero magnitude among the two adjacent active-current vectors, which produce smaller CMV, is selected to apply in the rectifier stage. The DPWM strategy reduces the peak magnitude of common-mode voltage by 42.3% while maintaining the advantages of the traditional DPWM modulation strategy such as less hard switching times in a carrier period, wide voltage transfer ratio, and input/output performance. Finally, the effectiveness of the modulation strategy is verified by simulation and experiments.

Introduction. Rectifiers are the most important converters in a very wide field: the transport of electrical energy in direct current and in the applications of direct current motors. In most electrical and electronic systems, rectifiers are non-linear loads made up of diodes, therefore they are a source of harmonic pollution at a base frequency with a distorting line current signal that generates electromagnetic interference. There are two disturbance modes: common mode and differential mode. These disturbances caused by the rapid variation of current and voltage as a function of time due to the switching of active components, passive components such as inductors, capacitors, coupling, etc. The purpose of this work is to study the conducted emissions generated by a rectifier connected to the Line Impedance Stabilizing Network in an electric circuit. The determination of these disturbances is done for firstly both common and differential modes at high frequency, and secondly harmonics current, line current at low frequency. The novelty of the proposed work consists in presenting a study of disturbance generated by rectifiers using simulation and also experimental measurements at low and high frequencies in order to compare the results. Methods. For the study of the disturbances conducted by the diode bridge converter (rectifier), the sources of conducted electromagnetic disturbances were presented in the first time. Then, the common and differential modes were defined. This converter was studied by LTspice Software for simulation and also experimental measurements at low frequency for harmonics current and high frequencies for disturbances in common and differential modes. Results. All the simulations were performed using the LTspice software and the results obtained are validated by experimental measurements performed in the APELEC laboratory at the University of Sidi Bel-Abbes in Algeria. The obtained results of conducted emissions at high frequency and total harmonics distortion of current at low frequency are compared between simulation and experiment., Вступ. Випрямлячі є найважливішими перетворювачами у дуже широкій сфері застосування: передача електроенергії постійного струму та застосування двигунів постійного струму. У більшості електричних та електронних систем випрямлячі є нелінійними навантаженнями, що складаються з діодів, тому вони є джерелом гармонійних «забруднень» на базовій частоті зі спотворенням сигналу лінійного струму, що генерує електромагнітні завади. Існує два режими завад: загальний та диференціальний режим. Ці завади викликані швидкою зміною струму і напруги в залежності від часу через перемикання активних компонентів, пасивних компонентів, таких як котушки індуктивності, конденсатори, муфти та ін. Метою даної роботи є вивчення кондуктивних випромінювань, створюваних випрямлячем, під‘єднаним до мережі стабілізатора повного опору лінії в електричному колі. Визначення цих завад проводиться, по-перше, як для загального, такі для диференціального режимів на високій частоті, а по-друге, для гармонічного струму, лінійного струму на низькій частоті. Новизна запропонованої роботи полягає у поданні дослідження завад, створюваних випрямлячами, з використанням моделювання, а також експериментальних вимірювань на низьких та високих частотах для порівняння результатів. Методи. Для дослідження завад, створюваних діодним мостовим перетворювачем (випрямлячем), вперше були представлені джерела електромагнітних завад, що виникають. Потім було визначено загальний та диференціальний режими. Цей перетворювач був вивчений програмним забезпеченням LTspice для моделювання, а також експериментальними вимірюваннями на низьких частотах для гармонійного струму та високих частот для завад у загальному та диференціальному режимах. Результати. Усі моделювання були виконані з використанням програмного забезпечення LTspice, а отримані результати підтверджені експериментальними вимірюваннями, проведеними в лабораторії APELEC в Університеті Сіді-Бель-Аббес в Алжирі. Отримані результати для кондуктивних завад на високій частоті та повних гармонічних спотворень струму на низькій частоті порівнюються стосовно моделювання та експерименту.

This article presents an interleaved boost rectifier for power factor correction (PFC) that operate in the continuous conduction mode (CCM) and is grounded on the switching cell with switching frequency modulation (SC-SFM). The input current naturally follows the shape of the input voltage, which is a resistive input characteristic (voltage follower). In the proposed converter, only one output voltage control loop is required. Moreover, the proposed topology has a wide range of soft commutation and no reverse recovery when the diodes block. This article presents the operating principle, a mathematical analysis of the converter, and four topological variations. In addition, experimental results of a 1-kW rectifier prototype with four different switch technologies (MOSFET, CoolMOS, SiC and IGBT), are discussed and their operational characteristics are demonstrated.

The efficiency of a rectenna varies under the influences of receiving polarization tilt angle, operating frequency, input power, and load value in different applications. Yet, no reported rectenna can realize stable efficiency when all these factors vary within a wide range. To solve this problem, an all-polarized rectenna is proposed in this paper, composed of a dual-input rectifier and a dual-polarized antenna. By introducing a novel six-port coupler, the rectifier maintains stable efficiency at wideband, wide input power and dc load ranges. Moreover, the efficiency of the rectifier keeps stable when the antenna receives power at different polarization tilt angles. Accordingly, a dual-polarized antenna with extended bandwidth and 3-dB beamwidth is implemented. Finally, the rectenna is formed. The prototype can maintain beyond 70% of the peak efficiency from 1.7 to 2.5 GHz. At a power density as low as 1 W/cm2, efficiency can reach 24.4%. Furtherly, the rectenna is demonstrated by forming a battery-less digital clock. The clock can be powered wirelessly by a WiFi router or cellular base station with maximum distances of 1 or 70 m respectively. Besides, the clock can successfully function under significant transmitting-direction deviation or polarization misalignment between the power source and the rectenna.

In this paper, a novel zero-voltage switching (ZVS) full-bridge converter is proposed to overcome the disadvantages of traditional phase-shifted full-bridge (PSFB) converter. In the proposed converter, a half-bridge (HB) converter with center-tap rectifier (CTR) is integrated into the traditional PSFB converter by sharing the lagging-leg switches and output filter. The HB converter operates with full duty cycle to ensure continuous energy transmission and the output voltage is regulated by adjusting the phase-shifted time of FB converter. The proposed converter has many advantages such as reduced filter requirement, wide ZVS range and low primary circulating current. In addition, the rectifier in the proposed converter is composed of a full-bridge rectifier (FBR) section and a CTR section. This feature makes the proposed converter well appropriate for the medium output voltage applications. Key operation principle and characteristics are fully discussed in this paper. The effectiveness of proposed converter is verified using a 1.2-kW prototype circuit with 280 V input voltage and 60-120 V output voltage.

Traditional wireless power transfer (WPT) systems usually adopt the triple-phase-shift (TPS) control method to maintain a constant output voltage, track the maximum system efficiency point (MEPT), and achieve zero-voltage-switching (ZVS) operation for various applications. However, these three targets are achieved at the cost of high reactive power on both primary and secondary sides, especially under light-load conditions, leading to low efficiency. This has become one of the challenges that hinder a further deployment of WPT technologies in practice. To address this vital problem, in this paper, how the reactive power lowers the system efficiency is revealed based on a mathematical model established. Then, a hybrid modulation control strategy based on a proper selection between the full-bridge and half-bridge modes of the inverter and active rectifier is developed. Besides, a detailed analysis of the switching boundary, i.e., selecting full-bridge or half-bridge, is provided. Finally, an experimental prototype is constructed to verify the effectiveness of the proposed control method. Experimental results show that the proposed method can reduce the reactive power, maintain a constant output voltage, and realize the MEPT and ZVS operation, with high efficiencies up to 94.29% in a wide load range.

LLC and CLLC resonant converters are good candidates for the isolated dc-dc stage in EV on-board chargers due to their capability of achieving zero-voltage-switching (ZVS) at full load range. The synchronous rectifier (SR) is usually utilized to reduce the conduction loss and improve the system efficiency compared with the conventional diode bridge rectifier. In this paper, a high-dv/dt-immune, fine-controlled and parameter-adaptive gate driving scheme is presented for GaN-based synchronous rectifier in EV on-board chargers. A novel self-driven SR drain-to-source voltage sensing circuit is proposed. The circuit provides a low-impedance bypassing path for the displacement current induced by the high dv/dt, which addresses the over-voltage and oscillation issues for the controller input. The detailed operating principles and the design considerations of the novel sensing circuit are discussed as well. Moreover, the adaptive SR on-time tuning algorithm is implemented, which avoids the influence from the loop stray inductance and the propagation delay in the path and reaches the SR zero current turn-off moment with fine accuracy. A 3.3 kW, 500 kHz CLLC resonant converter prototype is built to validate the proposed SR gate driving scheme. With the employment of the proposed gate driving scheme, the SR almost achieves zero current turn-off for the whole operating frequency range. The prototype demonstrates the peak efficiency of 97.6% and the power density of 130 W/inch3.

This paper proposes a new bidirectional isolated LLC resonant converter, which is suitable for ultra-wide voltage gain range applications, such as electric vehicle charging systems. The inverter and rectifier of proposed topology both have two modes by reconfiguring different modulation schemes during bidirectional operation. This results in three voltage-gain ranges, allowing ultra-wide output voltage operation and narrow modulation frequency. The conversion ratio and resonant tank can be designed for only a quarter of the required output voltage range. Finally, the proposed topology and analysis are validated by experiments results obtained from the converter prototype built in the laboratory

The hybrid LCC/VSC cascaded HVDC (HC-HVDC) scheme, in which the LCC is adopted as rectifier, and one LCC in series with multiple paralleled VSC based MMCs is adopted as inverter, combines the advantages of both LCC and VSC-MMC technologies. Presently, a HC-HVDC project is planned to deliver the power from Baihetan to Jiangsu in China. One of the major challenges is to suppress the DC overcurrent issue of VSC-MMCs especially under commutation failure condition of LCC at inverter side. Based on Baihetan-Jiangsu project under construction, the model of HC-HVDC system is developed in PSCAD/EMTDC. In the system, the rectifier employs a dual 12-pulse LCC, while the inverter adopts a hybrid scheme, i.e., one LCC converter in series with three paralleled VSC-MMC converters. This paper addresses the main cause and feature of the DC overcurrent, then proposes an overcurrent suppression control method for HC-HVDC system based on fuzzy clustering and identification approach. And the system transient performances with the proposed control approach are evaluated under AC fault conditions. The results show that the proposed approach can not only suppress the DC overcurrent following the commutation failure to a certain extent, but also improve the post-fault recovery performance of the overall system.

This paper proposes a novel approach to the modelling of HTS transformer-rectifier flux pumps that can charge HTS magnet-ic loads without the need for bulky current leads or expensive cryogenic requirements. The model was built in MATLAB/Simulink for a flux pump with 2 HTS switches, an HTS transformer with a primary inductance of 15 mH, second-ary inductance of 50 H and an HTS magnetic load with an in-ductance of 2 mH. With a 5 A pk-pk triangular current wave-form at 2 Hz the system can load the HTS load to 34.63 A in 5 s. This incremental addition of flux to the load demonstrates the advantage of flux pumps as they can charge high-field magnets without the need for large power sources. The speed of flux pumping is improved by increasing the system frequency, the magnitude of the dynamic voltage developed in the HTS switches and by increasing the primary inductance of the trans-former. This has widespread industrial applicability in fields such as the charging of high-field magnets for MRI systems.

In this paper, a basic capacitive power transfer (CPT) topology with series-parallel (SP) compensation is developed for load-independent step-up voltage output. There are three main contributions. First, the step-up constant-voltage (CV) output and zero-phase angle (ZPA) property are designed by using an h-parameter modeling method. Second, a current-source rectifier (CSR) is proposed at the secondary side and the working transient is analyzed. Third, the impact of parasitic resistances is investigated, and the output voltage attenuation and system efficiency are analyzed at different loads, coupling coefficients, and quality factors. A 130 W prototype is implemented with 150300mm metal plates. Experiments validate the CV output property with a step-up voltage gain of 2. The peak efficiency is 86.6% at a coupling coefficient of 0.16 and a transfer distance of 4mm.

The existence of inrush current poses a significant problem during the start-up process within three-phase voltage-source rectifiers. To address this problem, this study proposes a strategy to suppress the inrush current effectively based on the virtual-resistor- control method, while preventing the increase in cost of the system and complexity of the algorithm. First, a mathematical model is established based on the dq coordinate frame, and the primary cause of the inrush current is analyzed. Then, the design process of the virtual-resistor-control method is detailed. Finally, the accuracy and effectiveness of the proposed method are verified by simulations and experiments. The results show that the inrush current can be more than two times the rated current before the addition of the virtual resistor. The start-up process can be realized without the inrush current after the addition of the virtual resistor, it does not need to increase hardware costs, there is no secondary inrush current, and the sensitivity of the parameters and the complexity of control are low.

This paper presents an improved Virtual Flux-based Direct Power Control (VF-DPC) applied for a three-phase pulse width modulation rectifier. The proposed control approach incorporates an enhanced Virtual Flux estimator made up of a cascade second-degree low-pass filter. This latter guarantees the attenuation of the highest harmonics. The introduced control concept presented in this paper has interesting features such as reducing the current harmonics distortion. In other words, it ensures that the input current drawn from the power supply is perfectly sinusoidal whatever the state of the network voltage. The proposed method also allows to maintain the DC side capacitor voltage at the required level and assure that the input current is in phase with the respective voltage to satisfy the unity power factor function. The results obtained from the numerical simulation have proved the effectiveness of the proposed method for disturbed grid voltage and system parameters variation.

With low-power gadgets proliferating, the development of a small, effective rectenna is crucial for wirelessly energizing devices. A simple circular patch with a partial ground plane for RF-energy harvesting at ISM (2.45 GHz) band is proposed in this work. The simulated antenna resonates at 2.45 GHz with an input impedance of 50 Ω and a gain of 2.38 dBi. An L-section matching a circuit with a voltage doubler is proposed to provide excellent RF-to-DC transformation efficiency at low power input. The proposed rectenna is fabricated and the results show that the return loss and realized gain have good characteristics at the ISM band with 52% of RF-to-DC transformation efficiency, with an input of 0 dBm power. The projected rectenna is apt for power-up low sensor nodes in wireless sensor applications.

Розроблено методику вибору електрообладнання вентильного двигуна з машинною комутацією, що враховує способи керування інвертором. Встановлена потужність електрообладнання вентильного двигуна (ВД) визначається технологічними вимогами і залежить від структури перетворювача, способу комутації ключів перетворювача та способів керування інвертором. Застосування автономних інверторів зі штучною комутацією, ключі яких комутуються за рахунок реактивної енергії, накопиченої в додаткових комутаційних пристроях, підвищує коефіцієнт використання синхронної машини. Однак у цьому випадку ускладнюється схема і зростає встановлена потужність перетворювача. Використання транзисторів IGBT і тиристорів IGCT призводить до значного зростання вартості устаткування. Для зменшення впливу випрямляча ВД на мережу й узгодження напруги привода з напругою живленняможе виникнути необхідність в узгоджувальному трансформаторі і пристрої компенсації реактивної потужності. На величину потужності цього устаткування впливає спосіб керування випрямлячем, характер навантаження двигуна і діапазон зміни швидкості. Регулювання напруги випрямляча може бути симетричним і несиметричним. Відомо декілька способів несиметричного регулювання, серед яких одним з найдоцільніших є почергове. У випадку почергового керування в трифазній мостовій схемі створюється штучний нульовий контур, внаслідок чого тривалість протікання струмупо вторинних обмотках трансформатора стає меншою 2/3 напівперіоду живлячої напруги. Крім цього, підвищуються також енергетичні показники, зокрема зменшується споживання реактивної потужності та збільшуються коефіцієнти зсуву і потужності. A technique for selecting the electrical equipment of a valve motor with machine commutation has been developed, which takes into account the ways of controlling the inverter. The installed capacity of the electrical equipment of the valve motor (VD) is determined by technological requirements and depends on the structure of the converter, the method of commutation of the converter keys and the methods of controlling the inverter. The use of autonomous inverters with artificial switching, the keys of which are switched due to the reactive energy accumulated in additional switching devices, increases the utilization factor of the synchronous machine. However, in this case, the circuit becomes more complicated and the installed power of the converter increases. The use of IGBT transistors and IGCT thyristors leads to a significant increase in the cost of the equipment. To reduce the influence of the rectifier VD on the network and match the drive voltage with the supply voltage, a matching transformer and reactive power compensation device may be needed. The amount of power of this equipment is affected by the method of controlling the rectifier, the nature of the engine load and the range of speed changes. Voltage regulation of the rectifier can be symmetrical or asymmetrical. Several methods of asymmetric regulation are known, among which one of the most expedient is alternating. In the case of alternating control in the three-phase bridge circuit, an artificial zero circuit is created, as a result of which the duration of the current flowing through the secondary windings of the transformer becomes less than 2/3 of the half-cycle of the supply voltage. In addition, the energy indicators also increase, in particular, the reactive power consumption decreases and the shift and power coefficients increase.

Miniaturised piezoelectric devices are emerging energy harvesting sources that are appropriate for various implantable and wearable applications. However, these piezoelectric devices exhibit considerable internal resistance due to their internal impedance, which leads to self-start and low-energy conversion failures. This paper describes a dual-stage boost converter circuit by facilitating self-powering features and boosting the low voltage harvested by the piezoelectric devices into dc. The proposed circuit comprises conversion stages of ac-dc and dc-dc in Stages I and II, respectively. In addition, the proposed circuit does not require employing the auxiliary circuits to generate the train pulses by triggering the bidirectional switches to envelop the current being stored in Stage II and kick-start the self-powered circuit for piezoelectric energy harvesting systems. Theoretical assumptions and control strategies were tested and verified with ideal and impedance input sources. The proposed circuit could convert a low voltage of 3 Vac into 19 Vdc. The maximum attained output power by the proposed circuit was 3.61 mW. The outcome depicted that the proposed circuit boosted the low voltage and outperformed the existing literature circuits in terms of output voltage and power.

Active Front-End (AFE) rectifiers have regained momentum as the demand for highpower Electric Vehicle (EV) charging infrastructure increases exponentially. AFE rectifiers have high efficiency and reliability, and they minimize the disturbances that could be generated due to the operation of the EV charging systems by reducing harmonic distortion and operating close to the Unity Power Factor (UPF). The purpose of this review is to present the current state-of-the-art AFE rectifiers used in fast chargers, focusing on the comparison between different AFE topologies and their components, as well as modular AFE solutions. Furthermore, different control strategies of AFE converters are presented and compared. Some of their more widely used control techniques, namely Voltage Oriented Control (VOC), Direct Power Control (DPC), Hysteresis Current Control (HCC), and Model Predictive Control (MPC), have been implemented, and their performance compared. Centralized and distributed control systems are compared for operating parallel AFE rectifiers for modular, fast charging systems. An overview of cooling systems and reliability evaluation tools is also presented. Finally, trends and future outlooks are analyzed.

In this paper, a series-series wireless power transfer (WPT) system combined with an inverse coupled current-doubler rectifier (ICCDR) is proposed, as a very appropriate WPT topology for high current applications. The ICCDR uses an autotransformer to reduce the losses on the rectifier stage, which is suitable for high current low voltage output applications. Furthermore, a comprehensive comparison between the proposed WPT system with ICCDR and the traditional WPT system with diode rectifier is presented. In the proposed WPT system, the primary parameter configuration and circuit behavior keep the same, while the secondary side altered, contributing to a volume reduction on the resonant capacitor. The system overall efficiency and power density are improved significantly. Accordingly, a 10kW 400V/48V WPT prototype for battery charging is constructed and tested to validate this proposal. The output voltage is in the range between 38 Vdc and 55 Vdc, and the rated output current is 200A. The overall efficiency of the proposed system reaches 94%, improving 2% efficiency with 220W energy saving with respect to the traditional diode-rectifier system, when 9.5kW output power is delivered. Theoretical analysis and experimental results have verified that the proposed system shows great advantages in high power WPT applications.

As for bidirectional LLC converter, conventional pulse frequency modulation is typically adopted in the reverse mode resulting in a low voltage gain of reverse LLC. Then the bus voltage may be lower than peak grid voltage, which causes the buck-type inverter cannot output 220 Vac and poses series challenge for bidirectional operation. A bidirectional synchronous / asynchronous rectifier control is proposed for wide battery voltage applications in LLC converter. In the forward mode, the secondary-side switching devices are regulated as synchronous rectifiers (SRs) and a simplified model is built to calculate the SR on-time. In the reverse mode, with the same conduction time, the turn-on instants of primary-side and secondary-side switches are asynchronous and controlled with a delay angle. The proposed control not only achieves the forward LLC SR function with low microcontroller calculation resources, but also helps the reverse LLC obtain high voltage gain. A 6.6-kW SiC bidirectional LLC charger was built. By using the proposed control, the forward LLC efficiency improves 0.2% compared to conventional SR method. In the reverse mode, the LLC voltage gain is up to 1.33 so that the charger can output 220 Vac in the wide battery voltage range of 200 V~500 V.

During the typical constant current (CC) charging process, the supercapacitor has a pretty wide-range load variation. However, an inductive power transfer (IPT) converter can only maintain high efficiency within a certain load range around its optimum load point. Once the supercapacitor load resistance is far away from the optimum point, which usually happens in low charging power levels, i.e., the smaller load resistances, the IPT converter will suffer from the dramatic efficiency degradation and thus a step-up load transformation is required throughout the whole charging process. In this paper, a novel current-controlled semi-active rectifier (CCSAR) based IPT converter is proposed to fulfill this requirement. The characteristic of step-up load transformation is firstly identified and implemented by controlling the conduction angle of the CCSAR to enhance the efficiency in the charging process. The desired charging CC is then regulated by tuning the operating frequency of the IPT inverter. To coordinate these two objectives, a bivariate control is adopted here to achieve fast, direct and precise current output with enhanced efficiency performance over the whole load range during the CC charging process. Finally, experiment results validate the theoretical analysis well.

Nowadays, the scale of power grid is remarkably increasing and there is a continuous reinforcement of AC–DC hybrid systems. Thus, the single-phase grounding fault currents on the AC grid-side of rectifier and inverter stations increase significantly, which may exceed the capacity limit of the circuit breakers. The large short-circuit currents would result in problems during equipment selection and threaten the safety of equipment and personnel. To solve such issue, the effect of the converter transformer on the single-phase grounding fault current on the grid-side is analyzed. The mechanism of high short-circuit current in DC near region is revealed. Also, the feasibility of neutral point earthing via small reactor at HVDC converter transformer to suppressing the single-phase grounding fault current is verified. In addition, the principle of selecting the suitable small reactor is summarized. The results show that the neutral point earthing via small reactor at converter transformer can effectively limit the single-phase grounding fault current on the AC-side. However, it would lead to an increase of overvoltage at the neutral point of HVDC transformer. Therefore, neutral grounding by small reactor might be implemented when the insulation level is satisfied.

Virtual synchronous machine (VSM) based high voltage dc systems enhance the inertia of the power system. However, the dynamic interactions between the VSM-based rectifier station, the inverter station, and the grid could induce the system oscillation, which has been investigated in this article. At first, the hybrid ac-dc impedance models of the VSMs considering the coupling between the ac and dc dynamics are established. Then, the relationships between the dc impedance, dq-frame impedance, and the hybrid ac-dc impedance are presented. It is found that the dc impedance of the VSM-based inverter station and the d-d channel impedance of the dq-frame impedance of the rectifier station behave as negative resistors in the low-frequency range. Moreover, a five-dimensional impedance stability criterion based on the hybrid ac-dc impedance and generalized inverse Nyquist criterion is proposed to assess the system stability. The analysis results show that the low-frequency oscillation occurs when the grid short-circuit ratio of the rectifier station is small. Finally, the simulation and experimental results verify the impedance models and the stability criterion.

This paper proposes a novel three-phase hybrid rectifier topology and control method for high power electrolytic hydrogen production application. It is composed of a primary rectifier, i.e., a 6-pulse silicon controlled rectifier (SCR) and an auxiliary converter, including a pulse width modulation (PWM) voltage source converter (VSC) and a phase-shift-full-bridge (PSFB) converter. SCR undertakes most of the power consumed by electrolysis cell (EC), and the auxiliary converter can compensate dc current ripples and absorb ac current harmonics of primary rectifier simultaneously. Compared with high power PWM rectifier, the proposed hybrid rectifier can keep the main benefits of PWM rectifier, such as the low dc current ripple to realize improved efficiency of electrolytic hydrogen production and high grid current quality at ac side, while significantly reducing the cost. The effectiveness of proposed hybrid rectifier is verified by the simulation as well as experimental results.

The linear model of the three-phase voltage source rectifier (VSR) proposed before could not provide an accurate description for the stability and dynamics performance when the output power is high, the inductances are large or the boost ratio is high. Hence, an item of Right-Half Plane Zero (RHPZ), which contains the output power, the inductances and the boost ratio, is introduced into the linear model in this paper, where its derivation and physical interpretation are also provided. After the introduction, the quantitative analysis for the RHPZ effects, including the decrease of the stability, the deterioration of the dynamic performance and the overshoot of the DC-link voltage, are provided in this paper. According to the analysis, a novel control strategy is proposed to enhance the stability to improve the dynamic performance and to restrain the voltage overshoot. Finally, simulation and experimental results verify that this control strategy has a great validity to reduce the RHPZ effects.

Vibration energy harvesting using multiple piezoelectric transducers (multi-PZTs) can increase its output power and environmental adaptability. At present, there are still few researches on multi-input interface circuits for multi-PZTs, especially those using the parallel synchronized switching harvesting on inductor (PSSHI) technique. Therefore, this article presents a self-powered dual-inductor MI-PSSHI-VDR interface circuit. It can process multi-PZT voltages with arbitrary phases input. The measurements demonstrate that the prototyped MI-PSSHI-VDR circuit can extract a peak power of 1.93 mW from four PZTs under an excitation of 1.5 g and 75.5 Hz. The energy integration efficiency and energy extraction efficiency of the prototyped circuit are 93.2% and 75.1%. Compared with a multi-input full-bridge rectifier, the proposed circuit can achieve 3.22 power improvement and 3.58 voltage improvement, which grasps a good balance between the indexes of peak output power and load voltage range. Additionally, the MI-PSSHI-VDR circuit is easy to implement and shows a good scalability, which can be an alternative solution for multi-PZTs energy harvest

Integrated generator-rectifier architecture has been shown to substantially improve power density, efficiency and reliability of the electric drivetrains in wind turbines. From a power-electronic perspective, the architecture processes a majority share of the incoming power through passive diodes operating at the generator’s fundamental frequency. This paper presents a design methodology of a 10 MW generator, which involves a specific low-reactance generator to minimize the commutation voltage drop at the passive rectifiers as well as prevent power imbalance between different generator ports. Appropriate phase shifts between the multiple passive ports to eliminate the need for a dc-link capacitor improve the drivetrain reliability. The proposed design adopts a slotless permanent magnet (PM) generator, where the reactance is greatly constrained by eliminating the stator slots. In addition, a Halbach PM-array structure reduces the reactance by removing the rotor back iron. The design methodology uses these features along with a multi-objective optimization framework to maximize power density and efficiency while retaining a low reactance. Co-simulation of the generator and integrated power electronics shows that the proposed architecture is suitable for off-shore wind generators. Finally, a subscale generator is tested to verify the low-reactance design of the proposed generator.

This paper presents an improved full-bridge converter with a five-diode rectifier. The primary side circuit is composed of a full bridge with two transformers and two split capacitors. On the secondary side, five diodes are employed in the rectifier stage. By using the asymmetrical PWM signals, this converter can realize the ZVS of all switches and reduce the circulating current. The two transformers share the load power equally in whole load range. Compared with the other dual-transformer-isolated-full-bridge converters, the transformers in the proposed converter are easy to optimize because of the load power equal sharing. Furthermore, the output filter inductance is reduced, which reduces the loss and volume. According to the loss analysis, the proposed converter has higher efficiency compared with some other DC-DC converters. The experimental results of a prototype with 300-400V input voltage and 250V/4A output verify the performance of the proposed converter.