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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 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.

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.

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.

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.

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.

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.

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.

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.

This paper describes the detailed modelling of a vibration-based miniature piezoelectric device (PD) and the analysis modes of operation and control of a voltage doubler boost converter (VDBC) circuit to find the PD’s optimal operating conditions. The proposed VDBC circuit integrates a conventional voltage doubler (VD) circuit with a step-up DC-DC converter circuit in modes 1–4, while a non-linear synchronisation procedure of a conventional boost converter circuit is employed in modes 5–6. This integration acted as the voltage boost circuit without utilising duty cycles and complex auxiliary switching components. In addition, the circuit does not require external trigger signals to turn on the bidirectional switches. This facilitates the operation of VDBC circuit at very low AC voltage (Vac ≥ 0.5 V). Besides this, the electrical characteristics of VDBC circuit’s input (i.e., PD) perfectly concurs with the studied testing scenarios using impedance power sources (mechanical shaker). Firstly, the proposed circuit which can rectify the PD’s output was tested at both constant input voltage with varying excitation frequency and constant excitation frequency with varying input voltage. Next, a small-scale solar battery was charged to validate the feasibility of the performance of the proposed VDBC circuit. The proposed circuit achieved a maximum output voltage of 11.7 Vdc with an output power of 1.37 mW. In addition, the rectified voltage waveform is stable due to the sminimisation of the ripples. In addition, the performance of VDBC circuit was verified by comparing the achieved results with previously published circuits in the literature. The results show that the proposed VDBC circuit outperformed existing units as described in the literature regarding output voltage and power. The developed rectifier circuit is suitable for various real-life applications such as energy harvesting and battery charging.

Converters are one of the most sensible components of any power conversion system when it comes to electrical faults. Moreover, if these converters are used in a rotating system, as is the case with rotating rectifiers used in brushless synchronous machines, apart from also being exposed to mechanical effects and thus having a greater likelihood of failure, no access is available directly, causing a lack of available measurements for condition monitoring. This paper applies a model-based method to the online detection of open-diode faults, shorted-diode faults and exciter open-phase faults in the rotating rectifiers of brushless synchronous machines. The applied method relies on the comparison between the measured and the theoretical exciter field currents, the latter computed through a healthy machine model from the machine actual output values. The proposed protection strategy stands out for its computational simplicity and its non-invasiveness, which makes its industrial application straightforward without the need of any further equipment or adaptation. Its applicability has been verified through a double approach, on the one hand, through computer simulations, and, on the other hand, through experimental tests, achieving satisfactory results. The research conducted proves that with the proposed method, given reasonable measurement and model estimation typical errors of less than 5%, positive differences between the measured and the theoretical exciter field currents of more than 13%, 200% and 30% for open-diode faults, shorted-diode faults and exciter open-phase faults, respectively, are detectable with at least a 95% confidence interval.

Schottky contacts on fluorine implanted AlGaN/GaN heterostructures with the ideality factor close to unity and low on-voltage threshold are presented in this paper. An SF6 plasma anode pretreatment followed by a specific low-temperature annealing is also compared to a nonannealed sample. In addition, physical-model parameters are extracted by means of cryogenic temperature measurements to understand the conduction mechanisms involved in annealed diodes, showing better DC performances than their nonannealed counterparts. Furthermore, annealing induces a decrease of the ideality factor, which sets the field-enhanced thermionic emission as the main conduction mechanism, and reduces the tunneling reverse current leakage. This effect is attributed to the recovery of the plasma-induced damages.

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.

In this paper, a four-phase 8/10-pole dual armature-winding variable flux reluctance generator (DAW-VFRG) with double-redundant rectifier circuit is proposed for onboard generator. The proposed generator integrating four-phase VFRG and dual armature winding structure improves fault-tolerant capability and power density. Based on the airgap field harmonics analysis and winding function theory, the no-load back-EMF model and winding inductance model are deduced for determining the optimal stator/rotor pole combination. In addition, based on magnetic energy comparison, the influence of the connection categories between two sets of armature windings and rectifier circuits on output capability is also investigated when the saturation effect is considered. The key design parameters are globally optimized to improve the output capability and fault-tolerant capability simultaneously. Moreover, the electromagnetic performance of the proposed DAW-VFRG under both normal and fault condition is evaluated and compared with single armature-winding VFRG with half bridge rectifier. Finally, two prototypes are manufactured and tested to validate the finite-element predictions.

In the acdcac converter system, the second harmonic current (SHC) is generated by the acdc rectifier and the dcac inverter. If the SHC propagates to the intermediate dcdc converter, the current stress of the power switches will be increased, and the conversion efficiency will be degraded. Therefore, it is necessary to suppress the SHC in the dcdc converter. In this paper, the generation and propagation mechanism of the SHC in the acdcac converter system is analyzed. Then, from a perspective of control bandwidth and dc-bus port impedance, the basic ideas for reducing the SHC in the dcdc converter with different control targets are proposed. Based on that, the virtual-impedance-based control scheme is proposed to increase the input impedance and output impedance of the dcdc converter simultaneously. The realization and design guideline of the virtual impedance are also presented. Finally, a single-phase 3-kVA acdcac converter system is fabricated and tested in the lab. The experimental results are provided to verify the effectiveness of the proposed SHC reduction control scheme.

In this paper, a high-input power (> 30dBm) rectifier circuit for 2.45 GHz microwave wireless power transmission is presented. To overcome the shortcomings of traditional Schottky rectifier circuit, the novel rectifier circuit is designed based on a GaAs field effect transistor (FET) and a Schottky diode are together as the rectification part. A system-level verification demonstrates that the novel rectifier circuit has a potential application value for microwave wireless power transmission system. Measurement results show that higher input power range and MW-DC power conversion efficiency are realized at the same time by this design scheme. The maximum MW-DC conversion efficiency of the novel rectifier circuit can reach 74.42% when the input power is 30 dBm, and it is 20% higher than the peak conversion efficiency of traditional rectifier who without FET. In addition, the proposed rectifier circuit can operate with over 50% efficiency when the input power varies from 16 to 31 dBm, and has a good performance with the value of load ranging from 70 to 730, it is mean that the novel rectifier circuit is able to provide power for some electronic devices with different impedance.

To integrate large-scale islanded onshore wind power with different sizes, this paper proposes an integration system based on the cascaded hybrid HVDC transmission system, which consists of LCC and several MMCs in series connection at the DC side of the rectifier. A large-scale wind farm is connected with one LCC and one MMC while several medium-scale wind farms are connected with MMCs directly. Owing to the hierarchical integration arrangement, the operating flexibility can be improved with reduced capacity and the number of step-up interfacing transformers. A resilient DC voltage control is proposed for the integration system to adaptively redistribute power among the converters during wind power fluctuations. Firstly, the topology and operating characteristics of the wind power integration system are introduced. Then, a resilient DC voltage control is proposed to ensure stable operation during wind power curtailments. Finally, a simulation model of the hybrid cascaded HVDC transmission system is built in PSCAD/EMTDC to verify the effectiveness. The research results show that the system provides a new option for long-distance transmission of large-scale islanded wind power.

In this paper, a single-stage rectifier-less boost converter circuit (SSRBC) for piezoelectric energy harvesting from ambient vibration was proposed. The proposed rectifier-less circuit acted as a boost converter to extract energy from a piezoelectric device (PD). It combined the conventional boost, buck-boost methods using two split inductors and single filter capacitor. The proposed integrated circuit topology functioned in both positive and negative half cycles generated by the PD. In the proposed topology, inductors were invigorated by being enveloped with the current, which was produced by the PD through the switches. This facilitated active rectification of ultra-low AC (amplitude < 0.5 VP). Theoretical analysis, control strategies, simulation and experimental study, were presented. The proposed circuit was capable of converting a low amplitude AC voltage of 0.5 VP into 5.1 Vdc. The highest output power extracted by the proposed circuit was 281.1 µW, which outperformed existing circuits. It could potentially facilitate the advancement of vibration-based energy harvesting system for low power demand applications such as sensors, quartz watches and portable charging devices.

Vienna rectifier, which is a non-generative-boost type rectifier, is widely employed in electric vehicle charging system. Nevertheless, the Vienna rectifier faces the challenge of current distortion elimination, current ripple mitigation and neutral-point (NP) voltage balance. As these problems are mutually coupled, the conventional finite control set model predictive control (FCS-MPC) methods cannot solve these problems properly. To address these issues, a three-layer double vectors FCS-MPC method is proposed. In the first layer of the proposed FCS-MPC method, the sectors are divided and the candidate vectors are selected to reduce the current distortion. In the second layer of the proposed FCS-MPC method, the double vectors with optimal duty cycles are adopted to reduce the current ripples. In the third layer of the proposed FCS-MPC method, the NP voltage is balanced by selecting the redundant P-type small vector or N-type small vector. Through the proposed method, the current distortion elimination, current ripple mitigation and NP voltage balancing are realized at the same time. The effectiveness of proposed method has been verified by simulation and experiment.