Low Voltage Rating Research Articles

Hybrid switched‐capacitor‐based boost DC–DC converter with reduced voltage stress

AbstractThis article presents the new hybrid switched‐capacitor (SC)‐based transformerless DC–DC converter with a high step‐up capability and common ground features. The proposed hybrid SC‐based converter provides low voltage stress across semiconductor devices to utilize MOSFETs with lower Rdson and low voltage ratings. In addition, the diodes in SC cells with low voltage stress can reduce the reverse recovery power loss of the converter. Thus, the overall efficiency of the proposed hybrid SC‐based converter can be increased. The converter circuit, operating principle, and design guidelines of the proposed hybrid SC‐based converter are discussed. To confirm the performance of the proposed hybrid SC‐based converter, a detailed comparison study with the conventional hybrid SC converter is also presented. Finally, a laboratory prototype with 200 W and 25 to 200 V is set up to verify the effectiveness of the proposed hybrid SC‐based converter.

New strategy for Mg-air battery voltage-efficiency synergy by engineering protective film with cation vacancies on Mg anode surface

Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment, its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate. In addition to the microstructure of Mg alloy anodes, the properties of discharge product films are of great importance to the discharge performance. Herein, the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties. Through contrastive analysis, it is found that the sufficient Y3+ produced during the discharge process can substitute Mg2+ in Mg(OH)2 to introduce effective cation vacancies. The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency, and this can be attributed to an increase in the migration pathway for Mg2+, reducing the diffusion over-potential caused by the protective product film. This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.

Non-Isolated High Gain Interleaved DC–DC Converter with Voltage Multiplier and Switched Capacitor for Renewable Energy Systems

A novel non-isolated high-gain DC–DC converter for green energy employment is presented and analyzed. The proposed converter comprises a switched capacitor cell, passive clamp circuit, coupled inductors, and voltage multiplier unit. An interleaved boost converter (IBC) is placed on the input side of the proposed design. The voltage multiplier unit (VMU) with the secondary windings of the coupled inductors is located on the load side. It is used to accomplish interleaved power storage. The leakage energy of coupled inductor is recirculated to the load side, and the reverse recovery problem of diodes is effectively suppressed. As a result, a low-on-state resistance power switch with a low voltage rating is employed and minimizing conduction losses. The presented topology is suitable for sustainable energy applications due to its low operating duty cycle, high voltage conversion ratio, and higher efficiency. The output voltage causes substantially low voltage stress on semiconductor switches and passive elements. This proposed paper deals with simulation, parameter selection, experimental design, results and discussion. The simulation is verified using MATLAB/Simulink with a DC voltage of 30–517[Formula: see text]V. To validate the design analysis, a 1.5-kW experimental prototype is designed with a switching frequency of 10[Formula: see text]kHz and attained an efficiency of 96.07%.

SEPIC-Boost-Based Unidirectional PFC Rectifier with Wide Output Voltage Range

A novel unidirectional hybrid PFC rectifier topology based on SEPIC and boost converters is proposed, which is applicable to various industrial applications such as electric vehicle charging stations, variable speed AC drives, and energy storage systems. Compared to other rectifiers, the proposed SEPIC-boost-based rectifier exhibits continuous current on the AC side, lower voltage stress on the active switches, a wider range of DC output voltage, no auxiliary DC-DC converters, and a high step-up static voltage gain operating with low input voltage and a low step-up static gain for the high-input-voltage operation. These traits allow the SEPIC-boost-based rectifier to utilize smaller input-side harmonic filtering inductors and adopt active switches with lower voltage ratings, resulting in reduced conduction losses. Additionally, the proposed rectifier features power factor correction and high boost/buck voltage-gain capabilities, simplifying control for electric vehicle charging and expanding its range of applications. In this paper, the operating principle of the novel topology is presented first, and then the mathematical model of the proposed rectifier is built. Based on this, the comparison between the proposed topology and conventional boost and SEPIC converters is given. Furthermore, the control strategy, including the high-power-factor control and the balancing control to the DC capacitor voltages, is discussed. Finally, to validate the accuracy of the proposed rectifier’s theoretical research, a 500-W SEPIC-boost rectifier system has been constructed in the laboratory, generating a 200/120 Vdc output voltage from a 155 Vpk/50 Hz power source.

Solid State Pulsed Power Modulator With High Repetition Rate and Short Pulse Width for High-Speed Pulsed Lasers

This paper proposes a modular pulsed power modulator (PPM) with a short pulse width and high repetition rate for pulsed lasers. The presented PPM is based on the modular structure to use semiconductor switches with low voltage ratings since these switches have fast switching speed which is an essential requirement to generate short pulses. In addition, to make a short gate signal which is also needed to generate short pulses, a gate driver circuit which applies positive and negative voltages asymmetrically is proposed. Moreover, a heatsink structure to minimize the parasitic capacitances is presented for the high repetition rate. Furthermore, a DC-DC converter for the modular PPM is developed, which connects transformers in parallel at the primary side to achieve voltage balance without any compensation circuit. Experimental results from a 5 kV PPM with the pulse width below 20 ns and repetition rate of 1 MHz are presented to verify the proposed works.

An improved Z-source-derived converter for efficient PV integration

ABSTRACT This paper proposes a high-voltage (HV) gain non-inverting an improved Z-source (ZS)-derived non-isolated boost converter topology. The achievement of HV gain is facilitated through the astute's integration of a ZS, a switched capacitor (SC), and a boost cell that operates with a reduced duty cycle. In comparison with earlier developed topologies, the proposed topology uses fewer components and provides HV gain. In addition to this, the converter reduces voltage stress on semiconductors and passive components. As a result, low-voltage rating (small R ds(on) ) switches and diodes can be used to reduce conduction and reverse recovery losses, respectively. The converter emphasises on reducing device count while increasing device utilisation factor and accommodating a broad range of input variations; thus, it has potential application in HV low-power distributed photovoltaic (PV) systems. Additionally, the converter draws continuous input current from the low-voltage PV terminal. The proposed converter’s operating principle is thoroughly examined in stead state. A 400 W prototype has been developed to verify the operational efficiency and theoretical assertions of the converter, with a switching frequency of 100 kHz. The converter obtained a peak efficiency of 93.25%.

Carrier removal rates in 4H–SiC power diodes – A predictive analytical model

An analytical model for predicting the proton and neutron radiation-induced carrier removal in silicon carbide (4H–SiC) diodes, is developed. It is primarily aimed towards a fast calculation of the carrier removal rates (ηe) and critical fluence (above which the diode drift layer is fully compensated), for a wide range of particle energies and diode ratings. The model utilizes the NIEL (non-ionizing energy loss) concept along with the actual carrier removal rate values for SiC available in the literature. A comparison to Si power devices is also made. The results from the predictive model suggest that diodes with a lower voltage rating can sustain a higher particle fluence and displacement damage before their drift layers are fully compensated. This provides radiation hardening guidelines for 4H–SiC power diodes at a device engineering level, which can help improve the reliability of circuits in harsh environment applications, such as space. The model is validated through TCAD simulations incorporating the proton-induced defects, as well as experimentally by irradiating SiC diodes with 2 MeV protons. The extracted compensation levels are in good agreement with those predicted by the analytical model, validating its potential in predicting carrier removal rate of SiC diodes for radiation prone environments.

An improved coupled inductor‐based quadratic step‐up DC–DC converter with a high step‐up factor and reduced voltage overshoot on the power switch

AbstractMost coupled inductor‐based step‐up DC–DC converters encounter a significant voltage overshoot on their power switch due to the leakage inductance of the coupled inductor. So, they need additional bulky snubber circuits or a sophisticated procedure for coupled inductor design to reduce that effect. This paper proposes an improved coupled inductor‐based DC–DC converter, which provides a high quadratic voltage conversion ratio without excessive voltage stresses on the power switch. An active clamp circuit that operates with the zero‐voltage switching (ZVS) feature has been utilized for this aim. This feature allows the main power switch to be selected from low voltage ratings and low on‐resistance MOSFETs, which reduces conduction loss. The topology also benefits from continuous input current, high gain, high efficiency, and an appropriate number of components compared with the produced gain. In this article, the theory and operation of this converter are described by proposing the dc and small‐signal models, loss model, and continuous and discontinuous current modes (CCM and DCM) relations. Experimental results are represented to evaluate the performance of the proposed topology. For this purpose, a 240 V/240 W prototype has been designed and fabricated. Results confirm the above claims.

A ZVS-Based Non-Isolated High Step-Up DC–DC Converter With Low Voltage Stress for Renewable Applications

A high gain soft switched step-up DC-DC converter is presented in this paper. High gain is achieved at lower duty and turns ratio with a pair of coupled inductors and a voltage multiplier. In addition, an active clamp is incorporated to reduce the voltage stress across the main switch. Hence, switches with lower on-state resistance ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_dson</i> ) and lower voltage ratings are employed, reducing both conduction losses and cost. It additionally helps in achieving zero voltage switching (ZVS) to both MOSFETs. By recycling the leakage energy of the coupled inductors, voltage gain is further increased. It also helps to accomplish zero current switching (ZCS) turn-on and off of diodes. This further reduces losses and increases further efficiency. Moreover, the reverse recovery problem of the diodes is also mitigated. The working principle, steady-state analysis, and design guidelines have been carried out. Finally, a 500 W hardware set up with an input voltage range of 20-24 V and output of 400 V at a switching frequency of 50 kHz is built to validate the performance of the proposed converter. The operating efficiency at full load is observed as 95.11%.

A multi-level rectifier with voltage balancing capability for EV charging

ABSTRACT In two-stage electric vehicle (EV) battery chargers, ac-dc conversion stage contributes significantly in determining the power quality. At this stage, multilevel rectifiers (MLRs) featuring switches with lower voltage rating and better input voltage waveform quality can be adopted. However, balancing capacitor voltage in MLR is an important challenge. In this paper, a single-phase five-level power factor correction (PFC) rectifier with self-balancing capacitor is implemented for EV battery charging. The complimentary switching scheme adopted for rectifier reduces number of gate driver circuits and ensures capacitor voltage balancing. The rectifier shows added benefit of reduced voltage stress across switches and not requiring an external filter at the dc side as the load is parallelly connected with one of the capacitors. The operating principle, control strategy, modulation technique and design features of the implemented five-level rectifier is discussed in detail. The implemented control scheme enhances rectifier performance by establishing precise output voltage regulation during load fluctuations while maintaining unity power factor at input side. The five-level rectifier is validated experimentally and compared with other existing multilevel and non-multilevel rectifier topologies. The peak efficiency of 93.8% is achieved at 2 kW of output power.

An interleaved high step‐down coupled inductor based quadratic DC‐DC converter

AbstractA high step‐down direct current‐direct current (DC‐DC) buck converter with a coupled‐inductor in its topology is presented in this study. The switching pattern of the proposed converter is interleaved; therefore, the voltage stress on the semiconductors and the components is low since the primary high voltage will be divided between the blocking capacitors on the primary side. Thus, the voltage stress on semiconductor elements will be low. As a result, the preselected elements can be chosen with low voltage ratings. In addition, there are cells with coupled inductors utilized in the structure that helps the converter to provide improved voltage gain in its output terminal. Typically, narrow duty cycles are needed to achieve high gain in conventional buck converters, but the proposed converter has obtained a high conversion ratio even with wider duty ratios. Besides, the proposed converter has a constant equation for the voltage gain for the whole range of duty cycles. Theoretical analysis and comparison with other recent converters of similar types have been conducted to demonstrate the proposed converter performance. Furthermore, to verify the theoretical analysis, a 600 W prototype of the proposed converter with 820 V/30 V is implemented, and experimental results are presented.

Control of a Hybrid Shunt FACTS Compensator for Voltage Collapse Prevention in Interconnected EHV Power Transmission Systems

This article presents the converter topology for a hybrid shunt compensator (HSC) and its control suitable for an extra-high-voltage (EHV) power transmission system that helps to prevent voltage instability/collapse in multimachine interconnected power systems. Similar compensators combining a static VAR compensator (SVC) and a static synchronous compensator (STATCOM) have been proposed in the literature for power factor correction and active filtering, which are issues mostly related to the distribution system. However, for application in EHV transmission and voltage stability, the existing hybrid structures may not be suitable. This article particularly focuses on the prevention of voltage collapse that takes place in large EHV power transmission systems due to the mismatch of system-wide reactive power generation and consumption. The HSC proposed here is formed by the series combination of a STATCOM having a voltage rating of just 0.15 p.u. and an SVC having a voltage rating of 0.85 p.u. A suitable control strategy is formulated for the HSC that results in a modified operating ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$V\text{--}I$</tex-math></inline-formula> ) characteristic enabling the compensator to behave like a STATCOM (with a STATCOM of considerably low voltage rating) and inject constant current even when the voltage at the point of common coupling falls as low as 0.7 p.u.

An Extendable Interleaved Quasi Z-Source High Step-Up DC–DC Converter

A quasi z-source high step-up dc–dc converter is proposed here by integrating a coupled-inductor and a quadruple voltage rectifier technique. This converter can be used for high-voltage gain applications, without using extreme duty cycle and transformer high turns ratio values. Furthermore, low-voltage rating <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, which have small <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -resistances, can be used to reduce conduction losses and improve the converter efficiency. Also, single-core coupled inductors with multiwindings are used to reduce the magnetic components count. Using the interleaved technique at the converter input stage reduces the current stresses of the power <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s as well as the current stresses of the primary side windings of the coupled inductor. For high power applications, number of the input stage interleaved legs can be properly chosen to reduce the input current and output voltage ripples values, which reduce the input and output filters volumes. Leakage inductances energy recovery is another benefit of the given converter. To confirm performance of the proposed converter and its operating principles, as well as the given simulation results and mathematical analyses, a two-leg topology of the introduced converter has been implemented and tested by applying both interleaved and noninterleaved gate-drive signals at different conditions.

An Effective Controllable Grid Interface for Microgrids

The interest in the integration of distributed power generation and microgrids into power grids has significantly increased. In this context, interfacing microgrids with a host grid is of significant relevance, and therefore, in this paper, a cost-effective controllable grid interface for microgrids is proposed, modeled, and studied under various conditions, including smooth and abrupt power fluctuations, faults, and interface tripping. The proposed interface, named Microgrid Connector Controller (MGC), is an adequate and affordable alternative to the existing Back-to-Back (B2B) microgrid-grid interface, at a fraction of its capital costs. Thus, the proposed MGC’s performance is compared a B2B interface through detailed time-domain simulations in a realistic benchmark test system to demonstrate the controller’s capabilities. Compared with B2B, MGC’s direct frequency synchronization and power and voltage control capabilities makes it easier for microgrid operators to satisfy required standards and reduce wear and tear in grid equipment and customer loads. Finally, the MGC’s lower voltage ratings may translate into significantly smaller size and thus easier logistics and lower costs.

Multi‐agent voltage balancing in modular motor drives with series‐connected power electronic converters

AbstractModular motor drives can be considered as multi‐agent systems, in which the agents can work together to reach a common goal. One agent in such a modular motor drive consists of only a subset of the machine phases and power electronic converter modules, and is equipped with a dedicated controller. When the dc‐links of the different agents are connected in series to a single voltage source, giving rise to a so‐called stacked polyphase bridges converter, the power electronic converter components can have low voltage ratings. However, a voltage balancing controller must ensure that the total dc‐link voltage is distributed evenly among the agents when working in motoring mode. The goal of this research is to propose a multi‐agent voltage balancing algorithm based on dynamic average consensus, which depends solely on local computations, local measurements, and neighbour‐to‐neighbour communication. The scalability and reliability of the modular hardware are hence extended towards the control. Simulations and experimental results on a 4 kW modular axial‐flux PMSM demonstrate the feasibility of the concept.

Analysis and Experimental Validation of Single-Phase Cascaded Boost AC–AC Converter with High Voltage Gain

This article presents a single-phase cascaded AC–AC converter with boosting capability for power-quality issues. A high voltage gain can be obtained based on the number of cascaded units. The basic construction of one unit in the cascaded connection requires only two four-quadrant switches with a low-voltage rating. The performance features for the topology are a unity power factor that is close to unity on the input side, high steady-state performance, and fast dynamic response. The operation modes and mathematical model for the topology are presented. An appropriate PI-based control method/strategy is created, so the converter may continue to run while attaining the desired voltage gain, even if one of the cascaded units fails. The control circuit’s ability to maintain the continuity of matching the input current waveform with the input voltage waveform allows a decrease in the THD with different operating conditions. Moreover, the ability to solve a dead time problem carried out by the control circuit leads to a reduction in voltage stress. The effectiveness and robustness of the proposed technique were demonstrated via a computer simulation using MATLAB/Simulink. Moreover, an experimental setup for the system was built in the laboratory to validate the practicability of the system, which was tested under different conditions. The good agreement obtained between the theoretical and experimental results endorses the validity of the designed circuit.

Power Quality Enhancement Using Passive Power Filters

AbstractHarmonics in Power system are dangerous in electrical distribution power systems. Harmonics in the line current promotes instability, losses and also the voltage distortion. Due to properties of power electronics converters, power lines have become highly polluted. The problems of bad power quality are due to higher switching frequencies and the non‐linearity properties of power electronic devices. So, to compensate these problems priority is being given to the development of Power Filters. Both types of filters, i.e., passive and active are often used for harmonics producing load to avoid distortions. Shunt type filters influences the harmonic reduction at medium or high voltage level, whereas active filters have been declared for low or medium voltage ratings. Along distinct applications consisting the reactive power and harmonics compensation, passive filters are found to be suitable. Passive filters have been adopted for harmonic compensation in distribution systems due to low cost, integrity, reliability, and controls less operation. Therefore, to mitigate these harmonics, different topologies of passive filters are designed and their different combined performances in MATLAB/Simulink are evaluated. The filter can compensate harmonic currents, reactive power, and power factor. The simulation results presented in this research show that the proposed approach can provide good dynamic and steady‐state performance.

Edge-oxidation-induced densification towards hybrid bulk carbon for low-voltage, reversible and fast potassium storage

• An edge-oxidation-induced densification route was proposed to fabricate the bulk carbon with hybrid structure of both nanographitic domains and defect networks. • Fast and reversible K + intercalation can be ensured in sp 2 /sp 3 hybridized bulk structure, which is the key to enable carbon anodes with low charge voltage, high ICE, high-rate capability and excellent cyclic stability simultaneously. • The BC-2H//KPB full cell demonstrates great potential for high-performance potassium storage. Bulk carbon with high charge capacity at low voltage, high initial coulombic efficiency (ICE) and high-rate is critical but challenging for the practice utilization of potassium-ion batteries (PIBs). Herein, an edge-oxidation-induced densification strategy is reported to construct hybrid bulk carbon, in which the edge-oxygen of oxidized pitch serves as the cross-linking agent to in-situ conduct the densification. The nanographitic domains are constructed by the localized carbonization of aromatic hydrocarbon core, serving as low voltage intercalation sites. Meanwhile, the removal of oxygen groups builds bulk defect networks around nanographitic domains, thus ensuring fast K + diffusion kinetics. The hybrid bulk carbon anode performances high reversible capacity below 1 V (248.8 mAh g −1 at 0.05 A g −1 ), high ICE (68.2%), high-rate (209.9 mAh g −1 at 1 A g −1 ) and superior cyclic stability (90% capacity retention in 4000 cycles). Moreover, the full cell shows a significant discharge plateau at ca. 3.2 V and excellent cyclic stability (97% from cycle 10th to 200th). This work provides a rational and facile strategy to realize the tradeoff between K + intercalation and fast diffusion kinetics for practical application of PIBs, and gives deep insights into the mechanism of fast and reversible potassium storage at low voltage. An edge-oxidation-induced densification strategy is reported to construct sp 2 /sp 3 hybridized bulk carbon, in which the edge-oxygen of oxidized pitch serves as the cross-linking agent to in-situ conduct the densification. The nanographitic domains and defect networks in hybrid carbon materials is efficient to boost the low voltage potassium storage capacity, ICE, rate performance and long-term cyclic stability simultaneously.

A Step-Up Converter with Large Voltage Gain and Low Voltage Rating on Capacitors

Step-up converters are widely used in many applications, such as renewable energy generation with photovoltaic panels and fuel cell stacks. In many cases, the required voltage gain is larger for those applications than a traditional boost converter can achieve. Several large-voltage gain converters have been recently studied. This paper introduces a converter topology in which the voltage gain is larger than a traditional boost converter. The main advantages of the proposed topology are: (i) it provides a large voltage gain without the use of an extreme duty cycle; (ii) its capacitors require a smaller voltage to be sustained compared with other, similar state-of-the-art converters; (iii) the voltage among the ground input and output is not pulsating; and (iv) it can be synthesized with commercial, off-the-shelf half-bridge packed transistors. The proposed converter can be employed in different applications, such as distributed generation and microgrids. This paper presents the steady-state analysis of the proposed converter in the continuous conduction mode, a short comparison with similar topologies, and their voltage on capacitors. Computer-based simulation results are provided to verify the principle of the proposed converter in different operating conditions.

A high step‐up DC‐DC converter based on coupled inductor and diode‐capacitor with improved voltage gain and efficiency, and reduced voltage stress for photovoltaic systems

AbstractThis paper proposes a nonisolated high step‐up dc‐dc converter, which optimally integrates coupled inductor, and diode‐capacitor and provides superior features such as high gain, high efficiency, and low voltage stresses on power switches. Moreover, the common ground between the input and output of the proposed converter makes it appropriate for photovoltaic systems. It consists of two power switches, one inductor, one coupled inductor (CI), four diodes, and four capacitors. The power switches are exposed to low voltage stresses and are selected from low voltage ratings and low on‐resistance semiconductors. The topology, operating principle, complete steady‐state and ac small‐signal models, loss model, and design criterion are presented and described in detail. Also, the proposed topology is compared with other previous topologies. In order to evaluate the performance of the proposed converter, a 400 V/400 W experimental prototype has been designed and built. Experimental results validate the theory and show the converter produces high gain (14.25 times in the full‐load condition tested) and operates with high efficiency (94.9% in the full‐load condition).