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This paper presents an analysis of the operational characteristics of three-phase AC–DC matrix converters, which operate as rectifiers but possess a range of additional capabilities. These include the ability to reverse the power flow, control the input power factor, and generate a multilevel output voltage. The analysis yields a modulation strategy that minimizes switching losses. The proposed modulation strategy is compared with seven well-known space vector modulation strategies in terms of efficiency and distortion of input and output current. The performance is experimentally validated. [ABSTRACT FROM AUTHOR]

This article proposes a multi-resonant three-port DC-DC converter (MRTPC) that can achieve power decoupling in the presence of deviations in the parameters of the resonant elements. The MRTPC consists of a four-element resonant tank (FERT), a three-element resonant tank (TERT), and an LC resonant tank (LCRT). Due to the fact that the FERT can be configured with first and third resonant frequencies (RF), it can transmit the energy of the fundamental and third harmonic components. By reasonably setting the RFs of the FERT, TERT, and LCRT, decoupling control of primary and tertiary energy transmission can be achieved. Due to the characteristics of the FERT, TERT and LCRT at different frequencies, decoupling the transmission of the power of the primary and tertiary frequency components can be achieved even when there is a certain deviation in the parameters of the resonant elements of the FERT. This feature can effectively reduce the cost of selecting resonant elements. To improve the efficiency of the MRTPC, an optimized triple-phase-shift modulation strategy (OTPSMS) is proposed to minimize the root mean square value of the resonant current (RMSRC). For the nonlinear problem of minimizing the RMSRC, the KKT condition is used for the optimization solution. Finally, an experimental prototype with a power level of 1 kW is built to verify the theoretical correctness of the MRTPC and its OTPSMS. [ABSTRACT FROM AUTHOR]

The paper proposed a boost five-level inverter for wireless power transfer (WPT) system. It consists of one DC source, one inductor, one capacitor, and six power switches. It can produce a five-level output with an amplitude twice that of the DC source voltage. Compared with the existing five-level inverters, the proposed topology needs fewer power switches and energy storage elements, as well as lower power switches total standing voltage. Firstly, this paper introduced the topology and operating principle of the proposed inverter, established the mathematical models of the inverter output voltage and the system output power, and compared the proposed inverter with the existing five-level inverters. On this basis, the level cascaded extension method and topology of the proposed inverter were introduced and analyzed. Then, the modulation strategy and parameters of the proposed inverter were designed. Furthermore, the power loss of the proposed inverter was calculated. Finally, simulation and experimental verification were conducted. The results show that the inverter efficiency can reach up to about 94.5%, and the output THD can be as low as 24.47% or even lower. In addition, the transient response time is within 4 ms, proving the feasibility and superiority of the proposed inverter applied to WPT systems. [ABSTRACT FROM AUTHOR]

This paper presents short overview of the development and dissemination of specialized schemes and algorithms of space-vector-based synchronous multi-zone pulsewidth modulation (MZ PWM) for control of triple inverters of the medium-power variable speed drives characterized by relatively low switching frequency of inverters. It insures providing synchronization and symmetry of the basic voltage waveforms in triple-inverter-based configurations of drive installations on the base of standard voltage source inverters (VSIs). It assures also minimization of magnitudes of even-order harmonics and undesirable subharmonics in spectra of the basic voltages of drive installations, leading to reducing of losses in the corresponding apparatuses and to increasing of its efficiency. Examples of application of the basic techniques of multi-zone PWM for regulation of three typical structures of triple-VSI-based medium-power motor drives are presented. Modeling and simulations give a behavior of drive installations based on triple inverters adjusted by algorithms of synchronous MZ PWM. References 12, figures 11, table 1. [ABSTRACT FROM AUTHOR]

Summary: Single‐phase high‐frequency resonant inverters (SPHFRIs) with high power density, fast dynamic response, and high energy conversion efficiency have been widely studied and used in academia and industry. With the development of the modularization concept, the operation of multiple inverter modules is desirable because it can remove the limitations of cost, heat dissipation, and component volume in single inverter operation. However, a critical challenge in multiple inverter systems is that the both the phase and magnitude of the output voltage of each inverter module must be controllable to eliminate circulating currents between inverter modules. Great efforts have been made to solve this problem from three aspects: topology, modulation, and control strategy. In this paper, modulation strategies and topologies of different inverters are presented and reviewed to provide guidance to researchers working in this field. Firstly, multiple inverter system based on the SPHFRI is described and its advantages and disadvantages are analyzed. An important issue in the study of multiple inverter systems is presented, that is, the suppression of circulating current. Secondly, the circulating currents in a multiple inverter system are analyzed and derived from two aspects: (1) magnitude and phase angle and (2) active and reactive currents. Thirdly, the inverters used in the multiple inverter system are introduced, and their operating principles, advantages, and disadvantages are reviewed. A key comparison of several inverters is presented for the benefit of the readers. Fourth, through PI closed‐loop simulation, the performance of different multiple inverter systems for suppressing the circulating current is compared in two situations: (1) with magnitude discrepancy only and (2) with both magnitude and phase discrepancy. Finally, the advantages and disadvantages of each inverter are summarized, and the state of the art and future trends are presented. [ABSTRACT FROM AUTHOR]

In this paper an advanced modulation strategy is proposed that generates the switch control signals of a power converter while inherently guaranteeing zero-voltage switching (ZVS) operation. The proposed modulator is based on a first-order $\Delta \Sigma$-modulator combined with a hold-off circuit. This hold-off circuit consists of a D-latch and maintains the converter's switching state until ZVS commutation can be achieved while an integrator ensures the correct average output. Furthermore, features are implemented to improve start-up and transient behavior. The operating principle and stability of the proposed modulator is discussed and simulation results are presented. Finally, the proposed modulator is validated on a $2 \,\mathrm{k}\mathrm{W}$ GaN-based synchronous buck converter. Results show that the converter naturally operates under ZVS conditions by continuously varying its switching frequency without having to compute switching times or frequencies. The proposed method is an interesting alternative to pulse-width modulation especially when operating at high switching frequencies or when the switching loss in the power converter is significant.

This paper presents an analysis of the operational characteristics of three-phase AC–DC matrix converters, which operate as rectifiers but possess a range of additional capabilities. These include the ability to reverse the power flow, control the input power factor, and generate a multilevel output voltage. The analysis yields a modulation strategy that minimizes switching losses. The proposed modulation strategy is compared with seven well-known space vector modulation strategies in terms of efficiency and distortion of input and output current. The performance is experimentally validated.

This paper presents short overview of the development and dissemination of specialized schemes and algorithms of space-vector-based synchronous multi-zone pulsewidth modulation (MZ PWM) for control of triple inverters of the medium-power variable speed drives characterized by relatively low switching frequency of inverters. It insures providing synchronization and symmetry of the basic voltage waveforms in triple-inverter-based configurations of drive installations on the base of standard voltage source inverters (VSIs). It assures also minimization of magnitudes of even-order harmonics and undesirable subharmonics in spectra of the basic voltages of drive installations, leading to reducing of losses in the corresponding apparatuses and to increasing of its efficiency. Examples of application of the basic techniques of multi-zone PWM for regulation of three typical structures of triple-VSI-based medium-power motor drives are presented. Modeling and simulations give a behavior of drive installations based on triple inverters adjusted by algorithms of synchronous MZ PWM. References 12, figures 11, table 1.

Common-mode voltage (CMV) leads to the shaft voltage and shaft current by coupling the capacitor network in the permanent magnet synchronous machine (PMSM), which affects the reliability of the whole motor drive system. Based on the low-CMV modulation strategy for the PMSM drive system, this paper proposed an improved near-state pulse-width modulation (NSPWM) on switching loss. First, the generation mechanism for the switching signals of NSPWM was analyzed, and it was observed that there exists one phase of switches in an inactive state for every sector. Then, to reduce the switching loss of the NSPWM, this paper proposed an improved NSPWM modulation strategy based on power factor angle to adjust switching action, which ensures the switching tubes that have the biggest conduction current have no switching action. In addition, the switching loss analytic formula of the NSPWM was derived to prove the correctness of the proposed method for optimizing switching loss. Finally, the proposed modulation strategy was carried out in the simulation and experimental platform. Under the premise of good steady and dynamic performance, the results show that the proposed modulation strategy has less switching loss.

This paper proposes a sleep quality monitoring system based on artificial intelligence, whose basic idea is to collect the relevant data during sleep through the sensors installed in the intelligent devices and analyze the sleep characteristics, which include the data of body movement, respiratory data, snoring, etc. Then, under the synergy of this system, we propose a strategy to regulate sleep disorders by combining “artificial intelligence + physical exercise”. Then, under the synergy of this system, we propose a sleep disorder regulation strategy combining “artificial intelligence + physical exercise”. A total of 500 college students in the freshman and sophomore years of X University were selected as research subjects, and the Pittsburgh Sleep Quality Index (PSQI) and Physical Activity Rating Scale (PARS) were used to investigate the current status of the college students’ sleep quality and physical activity and to explore the specific effects of this control strategy. The results showed that the detection rate of PSQI score ≥8 was 179 (35.80%), and the average PSQI score of college students who participated in physical exercise was 8.31±2.34, which was significantly lower than that of college students who didn’t participate in physical exercise, which was 10.21±3.84. Under the combination of the “Artificial Intelligence + Physical Activity” sleep disorder regulation strategy, after the regulation of sleep quality and physical activity, the results were significantly lower than those of college students who didn’t participate in physical activity, which was significantly lower than those of college students who didn’t participate in physical activity. Under the combination of “artificial intelligence + physical exercise”, the average PSQI score after modulation (8.06±2.84) was also significantly lower than the average PSQI score before modulation (14.39±4.18).

Due to the problems of serious circulation current, large switching loss, high harmonic content, unstable voltage, and high engineering cost in existing microgrid structures, a micro-source half-bridge converter series Y-connection-based microgrid (HCSY-MG) is proposed in this paper. On the basis of the equivalent circuit in the system islanding state, the output characteristics of the system and the corresponding influencing factors under both square wave modulation and phase-shifted pulse width modulation (PS-PWM) are analyzed. Under single-cycle square wave modulation, since the DC-side capacitors of some micro-source half-bridge converters are affected by reactive power, which can result in system output voltage fluctuations or even an in-phase imbalanced state, a multi-period cycle modulation strategy is applied to solve this problem. Under the PS-PWM strategy, if the modulation degree and capacitance of the micro-source half-bridge converters are reasonably set, the output voltage of the system can be guaranteed to be in an in-phase equilibrium state. A simulation model and an experimental platform are built to verify the feasibility of the system and the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This publication provides a brief historical overview of the development of methods and techniques of pulsewidth modulation (PWM) for voltage source inverters, published mainly in Ukrainian publishing houses and in Ukrainian periodicals. Accent has been done to review of results of investigation of alternative methods and techniques of synchronous space-vector-based multi-zone PWM for inverters with low switching frequency. In particular, in the mentioned publications, the basic strategies, schemes, and algorithms of synchronous multi-zone modulation have been further developed, modernized, modified, and disseminated in relation to new promising topologies of power conversion systems, including: two-inverter-based electric drives with open-end winding of electrical motor; dual three-phase electric drives of symmetrical and asymmetric types; powerful six-phase systems based on four inverters, and two inverter-based and three-inverter-based photovoltaic installations with multi-winding transformer. It is shown that the developed schemes and algorithms of synchronous space-vector PWM, applied for control of inverter-based systems, provide continuous synchronization and symmetry of basic voltage waveforms of systems during the whole control range including zone of overmodulation of inverters. It provides minimization of even harmonics and undesirable subharmonics (of the fundamental frequency) in spectra of the basic voltages of systems, leading to reducing of losses in systems and to increasing of its efficiency. Based on a comparative analysis of the integral spectral characteristics of the phase and line voltages of systems, recommendations are formulated for the rational choice of schemes and algorithms of synchronous modulation for the relevant installations, depending on the modes of their operation. [ABSTRACT FROM AUTHOR]

Increased performance requirements in new power electronics areas of application, such as electric aircraft, make innovations on different design levels necessary. In order to quickly compare different topologies, analytical loss equations provide a fast and straightforward way to narrow down the possible solution space. The approach widely used in the literature results in long and complex terms, which can only be compared between different literature sources with great effort. Moreover, the literature lacks a detailed summarizing description of these analytical equations and their derivation, starting from the standard two-level VSI up to three-level midpoint clamped inverter topologies, such as the ANPC topology in its different modulation schemes. The application of such higher-level inverter topologies allows hybrid device configurations to become performant solutions. This work aims to give a closed-form description of the analytical loss modeling and the theoretical background and provide an implementation approach for a wide span of inverter topologies and for different modulation methods. [ABSTRACT FROM AUTHOR]

Metal–support interaction (MSI) is considered a key effect of electronic and geometric structures of catalysts on tuning catalytic performance. The oxygen evolution reaction (OER) is a crucial process during energy conversion and storage. However, the OER process requires the help of noble metal catalysts to reduce the reaction overpotential, enhance reactivity with intermediates, and maintain good operating stability. Carbon–supported metal catalysts have been considered candidates for noble metal catalysts for OER. MSI occurs at the interface of carbon supports and metals, affecting the catalytic performance through electronic and geometric modulation. MSI can influence the catalytic performance and change reaction pathways from charge redistribution, electron transfer, chemical coordination and bonding, and steric effect. Connecting MSI effects with the OER mechanism can provide theoretical guidance and a practical approach to the design of efficient catalysts, including the modulation of particle size, morphology, heteroatom doping, defect engineering, and coordination atom and number. Advantage can be taken of MSI modulation between metal compounds and carbon supports to provide guidance for catalyst design.

The modular multilevel converter (MMC) has proved to be a suitable converter topology for high-voltage direct current systems (HVDC). Some efforts can be identified in the literature to apply the MMC in static synchronous compensators (STATCOMs). However, the MMC has some challenges in the modulation schemes and energy storage requirements. Indeed, the literature has not presented a clear analysis of the modulation strategy impact on energy storage requirements. Thus, this paper introduces the spreading factor index to compare different modulation strategies in terms of capacitor voltage balancing capability. In addition, the impact of energy storage requirement on different modulation strategies is presented. In order to demonstrate the methodology, two strategies were selected: phase-shifted pulse-width modulation (PS-PWM) and nearest-level control with cell tolerance band algorithm (NLC-CTB). Subsequently, the MMC performance for each modulation strategy was compared in terms of energy storage requirements, capacitor voltage balancing capability, losses and current distortion. Besides, different operation conditions were analyzed in a case study based on a 15 MVA STATCOM. The results indicate that PS-PWM reduces the energy storage requirements, while the NLC-CTB modulation reduces the converter power losses. [ABSTRACT FROM AUTHOR]

Power converters have widespread applications in automotive, renewables, and power systems. The demand for power modules with low power consumption and high efficiency has increased due to advancements in semiconductor devices. So, power converters need to be highly efficient to reduce costs associated with energy dissipation and cooling requirements. This paper discusses various active thermal control methods for high-power power converters. It covers modulation and configuration techniques, ranging from single configurations to cascaded, modular, and multilevel converters. These concepts form the basis of power electronics building blocks, particularly relevant in all-electric ship systems. Power electronics building blocks represent a thriving technology that will advance ship power systems, the thermal design of which plays a crucial role in managing high heat dissipation levels. Hence, thermal management is essential for reliable device performance. The paper thoroughly studies different active thermal control methods and their impact on power semiconductor devices and converters, categorized per configurations, power routing methods, modulation, and control layers. The review then moves to thermal control methods for the PEBBs concept using multilevel converters in all-electric ship systems. The paper eventually outlines future research directions for the thermal aspect of power electronics building blocks.

After active neutral point clamped(ANPC) adopts SiC-MOSFETs, SiC-MOSFETs are easily damaged due to the excessive peak voltage. This paper establishes a single-phase parasitic inductance model of ANPC based on the SiC-MOSFET half-bridge modules. Then, based on this model, the cause of peak voltage on SiC-MOSFETs during ANPC commutation is analyzed. Finally, a short-loop commutation modulation strategy is proposed under the full working conditions of ANPC. The modulation strategy considers the influence of modulation carriers selection and dead time on ANPC commutation and optimizes the ANPC commutation loop to suppress the overvoltage on SiC-MOSFETs during ANPC commutation.

Metal–support interaction (MSI) is considered a key effect of electronic and geometric structures of catalysts on tuning catalytic performance. The oxygen evolution reaction (OER) is a crucial process during energy conversion and storage. However, the OER process requires the help of noble metal catalysts to reduce the reaction overpotential, enhance reactivity with intermediates, and maintain good operating stability. Carbon–supported metal catalysts have been considered candidates for noble metal catalysts for OER. MSI occurs at the interface of carbon supports and metals, affecting the catalytic performance through electronic and geometric modulation. MSI can influence the catalytic performance and change reaction pathways from charge redistribution, electron transfer, chemical coordination and bonding, and steric effect. Connecting MSI effects with the OER mechanism can provide theoretical guidance and a practical approach to the design of efficient catalysts, including the modulation of particle size, morphology, heteroatom doping, defect engineering, and coordination atom and number. Advantage can be taken of MSI modulation between metal compounds and carbon supports to provide guidance for catalyst design. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) has attracted considerable attention lately because of the high energy density and environmental friendliness of hydrogen energy. However, lack of efficient electrocatalysts and high price hinder its wide application. Compared to a single-phase metal oxide catalyst, mixed metal oxide (MMO) electrocatalysts emerge as a potential HER catalyst, especially providing heterostructured interfaces that can efficiently overcome the activation barrier for the hydrogen evolution reaction. In this mini-review, several design strategies for the synergistic effect of the MMO catalyst on the HER are summarized. In particular, metal oxide/metal oxide and metal/metal oxide interfaces are explained with fundamental mechanistic insights. Finally, existing challenges and future perspectives for the HER are discussed.

This paper presents the performance analysis of Series Active Power Filter (Series APF) based on five and sevenlevel neutral point clamped (npc) using modified instantaneous reactive power control strategy to use for harmonic and all voltage disturbances compensation. The conventional configuration based on standard voltage source inverter (VSI) with hysteresis controller presents several drawbacks such us uneven switching frequency and limited power applications. Multi-level inverters such us Five and seven-level are currently being investigated and used in various industrial applications; their advantages include the capability to reduce the harmonic content and decrease the voltage or current ratings of the semiconductors with low switching losses, low electromagnetic interference, and low acoustic noise. Fuzzy controllers are successfully employed in various industrial applications and are found more robust than conventional controllers; they represent a good alternative to classic control systems. To benefit of all these advantages two configuration of Series APF are presented in this paper adopting the same control scheme based on Phase Disposition-Sinusoidal Pulse Width Modulation (PD-SPWM) and fuzzy logic control (FLC). The proposed two series APF are evaluated using MATLABSimulink software and SimPowerSystem Toolbox for harmonic compensation and in case of all voltage disturbances compensation. The simulation results show the performance and the efficiency of the proposed Series APF based on seven-lever (npc) inverter in the improvement of the power quality. [ABSTRACT FROM AUTHOR]

Impedance-source inverters provide a promising single-stage power conversion with boost-buck capabilities and inverter legs short-circuit immunity. To achieve superior thermal and output harmonic performance, two novel discontinuous modulation strategies for the three-phase quasi-Z source inverter, called the maximum-boost discontinuous space vector modulation (SVM) and the simple-boost discontinuous SVM respectively, are proposed in this article. By properly arranging the shoot-through states and clamping a certain switch to the positive or negative dc-link rail during one-third of the fundamental period, reduced thermal stresses and superior total harmonic distortion performance can be achieved. The proposed modulation strategies are analyzed and compared to the conventional ones in terms of current stresses, power losses, thermal stresses, and output harmonics. Finally, simulations and experimental tests are carried out to validate the performance of the proposed modulation strategies and verify the presented analysis. [ABSTRACT FROM AUTHOR]

Electrolysis of water is an important process for producing green hydrogen, but high overpotentials on electrodes and slow reaction kinetics restrict its further development. This review combines experimental results, advanced characterizations and theoretical calculations to provide an in-depth analysis of the modulation strategies of cobalt-based catalysts for water electrolysis, which is conducive to the promotion of the industrial application. [Display omitted] • Various strategies to improve the performance of cobalt-based catalysts are detailed introduced. • Various cobalt-based catalysts are classified and summarized for water splitting. • Applications of in situ characterization techniques are discussed. • The challenges and prospects of cobalt-based catalysts for water splitting are proposed. Water electrolysis is an environmentally sustainable technique for producing highly pure hydrogen, which is essential for meeting the renewable energy demands of modern society. However, the practical applications of hydrogen/oxygen evolution reactions (HER/OER) are constrained by their slow kinetics and the dependence on noble metal catalysts (e.g. Pt, IrO 2 and RuO 2). In recent years, cobalt-based catalysts have attracted much attention due to their unique electronic structure and low cost, demonstrating broad application prospects in the field of catalysis. Nevertheless, the low conductivity, poor intrinsic catalytic activity, and limited active sites of cobalt-based catalysts make them difficult in practical applications. This review systematically introduces the design strategies to improve the intrinsic activity of cobalt-based catalysts, including structure and morphology control, heteroatom doping, defect engineering, interface engineering, and support effect. Subsequently, the recent advancements in cobalt-based catalysts for water electrolysis are discussed, emphasizing the structure–property relationship. In addition, the innovative use of in-situ characterization technologies in the understanding of reaction mechanisms is explored. Finally, the challenges and perspectives of cobalt-based catalysts are prospected. [ABSTRACT FROM AUTHOR]

Increased performance requirements in new power electronics areas of application, such as electric aircraft, make innovations on different design levels necessary. In order to quickly compare different topologies, analytical loss equations provide a fast and straightforward way to narrow down the possible solution space. The approach widely used in the literature results in long and complex terms, which can only be compared between different literature sources with great effort. Moreover, the literature lacks a detailed summarizing description of these analytical equations and their derivation, starting from the standard two-level VSI up to three-level midpoint clamped inverter topologies, such as the ANPC topology in its different modulation schemes. The application of such higher-level inverter topologies allows hybrid device configurations to become performant solutions. This work aims to give a closed-form description of the analytical loss modeling and the theoretical background and provide an implementation approach for a wide span of inverter topologies and for different modulation methods.

The Dual Active Bridge (DAB) DC-DC converter has the ability of bidirectional power transmission and the modulation scheme that is easy to implement, which can ensure the efficient transmission of energy in the system. Therefore, it is often used in various scenarios of small DC grid, such as energy storage, photovoltaic system, electric vehicle charging and so on. The main methods to improve the efficiency of dual active bridge include reducing the effective value of current and widening the soft switching area. Based on the above idea, an optimized extended phase-shift (EPS) modulation strategy is proposed in this paper. The modulation strategy achieves the goal of reducing the effective value of the current through the constraint optimization of the corresponding variables, and then improves the efficiency of the converter. In this paper, the working principles of several typical modulation strategies are introduced in detail, and then the power characteristics and soft-switching characteristics of the new method and other commonly used modulation schemes are analyzed and compared. Finally, the effectiveness of the optimization method for extended phase-shift modulation strategy is verified by the dual active bridge experimental prototype.

This publication provides a brief historical overview of the development of methods and techniques of pulsewidth modulation (PWM) for voltage source inverters, published mainly in Ukrainian publishing houses and in Ukrainian periodicals. Accent has been done to review of results of investigation of alternative methods and techniques of synchronous space-vector-based multi-zone PWM for inverters with low switching frequency. In particular, in the mentioned publications, the basic strategies, schemes, and algorithms of synchronous multi-zone modulation have been further developed, modernized, modified, and disseminated in relation to new promising topologies of power conversion systems, including: two-inverter-based electric drives with open-end winding of electrical motor; dual three-phase electric drives of symmetrical and asymmetric types; powerful six-phase systems based on four inverters, and two-inverter-based and three-inverter-based photovoltaic installations with multi-winding transformer. It is shown that the developed schemes and algorithms of synchronous space-vector PWM, applied for control of inverter-based systems, provide continuous synchronization and symmetry of basic voltage waveforms of systems during the whole control range including zone of overmodulation of inverters. It provides minimization of even harmonics and undesirable subharmonics (of the fundamental frequency) in spectra of the basic voltages of systems, leading to reducing of losses in systems and to increasing of its efficiency. Based on a comparative analysis of the integral spectral characteristics of the phase and line voltages of systems, recommendations are formulated for the rational choice of schemes and algorithms of synchronous modulation for the relevant installations, depending on the modes of their operation. References 30, tables 2, figures 25.

To overcome the challenges of large reactive energy transmission loss and high current stress, which ocurr during the operation of auxiliary commutated circuit (ACC) of novel parallel resonant dc-link inverter (PRDCLI), an improved modulation strategy for reactive energy transmission loss is herein proposed based on the discontinuous pulsewidth modulation (DPWM), which adopts sawtooth carrier wave with alternating positive and negative slopes and shunt dead zone. Compared with the original modulation strategy, based on minimizing the ACC operation frequency, the proposed modulation strategy is able to realize all switches soft-switching, and avoid the superposition of resonant current and load current during the operation of ACC, thus, effectively reducing the reactive energy transmission loss and the current stress of auxiliary switches of the ACC. Under the proposed modulation strategy, the equivalent circuits in different operation modes are divided, and the operation principle, voltage/current stress, loss distribution, and optimal parameter design method of novel PRDCLI are researched. Eventually, the proposed modulation strategy is verified by experiments on a 5-kW/40-kHz prototype made by SiC mosfet. [ABSTRACT FROM AUTHOR]

This paper proposes a dual-Trans-quasi Z-source three-level indirect matrix converter (DTrans-qZs TLIMC). A dual-Trans-qZs network is located in the DC-link of a TLIMC to provide a stable virtual neutral point for the inverter stage and to increase the voltage gain of the converter. The space vector pulse width modulation (SVPWM) strategy is proposed to control the DTrans-qZs TLIMC. By analyzing the small signal model of the DTrans-qZs network, the analysis result of the impact of the rectifier stage output voltage pulsation on the operating characteristics of the DTrans-qZs network can be obtained, and the modulation ratio of the inverter stage can be corrected in real time. By analyzing the voltage transfer ratio of the DTrans-qZs TLIMC, the calculation expression of the maximum voltage transfer ratio can be obtained. Finally, experiments are performed to verify the correctness of the topology and its modulation strategy. [ABSTRACT FROM AUTHOR]

In order to reduce the operating frequency and loss of the auxiliary commutation circuit (ACC) and current stress of auxiliary switches of a parallel resonant dc-link inverter (PRDCLI), this article proposes a novel space vector pulsewidth modulation (SVPWM) method. The novel SVPWM method can reduce the number of operations of the ACC to once in every PWM cycle on the premise of realizing soft switching of all switches, thereby reducing the operating frequency and loss of the ACC. At the same time, by adding the shunt dead time, the novel SVPWM method can avoid the superposition of the resonant current and load current, thereby minimizing the current stress of auxiliary switches. In addition, the novel SVPWM method can apply to any PRDCLI with the ability of variable zero voltage durations. Under the novel SVPWM method, according to the equivalent circuits of different operation modes, the operation principle, soft switching realization conditions and parameter design methods of the inverter are analyzed. Finally, a 10-kW/16-kHz prototype is built using insulated gate bipolar transistors to verify the validity of the novel SVPWM method. [ABSTRACT FROM AUTHOR]

A novel carrier-based discontinuous pulsewidth modulation (CB_DPWM) strategy for T-type three-level converter is proposed in this article. Because one significant advantage of the proposed CB_DPWM is the reduction of common mode voltage (CMV), it is named as RCMV_CB_DPWM hereafter. It also can reduce switching loss and remove dc offset from the neutral point voltage (NPV) simultaneously. RCMV_CB_DPWM has two design freedoms, one is modulation wave and the other is carrier wave. By injecting zero sequence voltage properly, the corresponding clamping mode can be acquired. Moreover, reduced CMV can be achieved by arranging carrier wave flexibly. The integrity of RCMV_CB_DPWM is analyzed as well as its NPV self-equilibrium ability, and an active NPV control method is then introduced. Moreover, its realization is discussed briefly. Finally, the experiments are carried out to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this paper, a carrier-based modulation strategy with planned zero sequence voltage (ZSV) injection for T-type three-level inverter (TLI) is proposed to control neutral point (NP) voltage, which is simple to be implemented. This strategy is analyzed comprehensively based on the relationship between NP current and the injected ZSV in one switching cycle. The planned ZSV is calculated according to the voltage difference between upper and lower capacitors and the injectable ZSV range without over-modulation. Furthermore, in order to reduce switching losses, the closest clamping mode method is applied, in which specific ZSV is injected to form discontinuous pulse width modulation (DPWM), and the NP voltage control ability is sacrificed to some extent. In most applications of the two proposed methods, the NP voltage can be perfectly controlled almost like virtual space vector PWM (VSVPWM). However, the switching numbers of the strategy with planned ZSV injection are a third even half less than that of VSVPWM. And the switching numbers of the closest clamping mode method are even a third less than that of SVPWM. Comprehensive experiments are carried out to verify the feasibility of the proposed two methods.

As the grid-connected AC-DC converter is the key equipment that links the low voltage direct current (LVDC) microgrids and the utility grid, the safe and stable operation of the converter is of great significance to improve the reliability of the LVDC microgirds. Since the converter's reliability is affected by the converter's topological structure and modulation strategy, a civil LVDC microgrid case study is analyzed, and the power losses, thermal stresses, lifetimes and reliability of components in the AC-DC converters with different topologies and modulation strategies are evaluated in this paper. The influence of these two factors on the reliability and efficiency of the converter is discussed, and the normalized weighted total harmonic distortion (NWTHD) with different modulation strategies is analytically determined and compared. The results show that when the converter operates with unity power factor in this application scenario, among the two-level converter, flying capacitor converter, neutral point clamped (NPC) converter and T-type converter, the T-type converter has the highest reliability. The effects of the converter's topology and modulation strategy on the capacitor reliability are relatively small. In view of reliability and power quality, third harmonic injection pulse width modulation (THIPWM) or space vector pulse width modulation (SVPWM) is more suitable for the converter in this microgrid.

A double-input bidirectional dc–dc converter, with an innovative architecture, exploiting the use of only three switches, is taken into account in this article. The modulation strategy proposed in the technical literature for controlling such a converter leads to a very low efficiency at low-load because the converter is only able to operate in continuous conduction mode when currents are low. A new modulation strategy, for exploiting discontinuous conduction mode, is here proposed. The efficiency increase is evaluated with a MATLAB/Simulink Plecs simulation model. The control algorithm and the simulation model are validated with experimental results carried out on a converter prototype. [ABSTRACT FROM AUTHOR]

The active circulating current suppression may cause high-frequency current ripple in the dc link of modular multilevel converters (MMCs). In this article, a phase-shifted double-group multicarrier-based phase-disposition pulsewidth modulation strategy is proposed to eliminate the dc-link high-frequency current ripple of MMCs, where the fundamental frequency component and the second-order component of the arm reference are modulated, respectively, by two groups of carriers. By shifting the phase angles of double-group multicarrier in each carrier period, the high-frequency current ripple injected into the dc link of MMCs can be eliminated. The proposed strategy not only eliminates the dc-link current ripple, but also extends the active and reactive power region of MMCs in comparison with the existing method. Simulation and experimental studies are conducted, and their results verify the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

This article proposes an improved DC-link series IGBT chopping strategy for the brushless DC motor (BLDCM) drive equipped with a small DC-link capacitor fed by single-phase AC source. In this strategy, different vector sets are established according to the switching state of the DC-link IGBT and the operation mode of BLDCM. By analyzing the effect of each vector on phase current change rate, a vector selection-based current control scheme is presented. In particular, when the rectifier output voltage is less than the average line voltage of BLDCM, the combined action of vectors with only DC-link IGBT chopping is designed, in order to decrease the converter switching times and reduce the DC-link capacitance at the same time. In addition, the constraint of the DC-link capacitor voltage is analyzed to satisfy the reliable regulation of the motor phase currents, and the calculation method of the DC-link capacitance is given furthermore. The proposed strategy can achieve the smooth operation of the motor with small DC-link capacitance. Meanwhile, the total switching times of the converter are reduced, thereby improving the converter efficiency. The contrastive experimental results verify the correctness of the theories and the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

Nine-switch converter has promising application prospects in fields where cost, volume and power density are required. The performance of the converter depends to a large extent on the modulation strategy. The existing SVPWM strategy for nine-switch converter requires a lengthy zero-vectors table to make over-modulation judgment, which increased the complexity of the algorithm and the runtime of the program. To improve performance, a novel simplified SVPWM strategy for nine-switch converter is proposed in this paper. The zero-vectors table is replaced by a set of simple formulas for over-modulation judgment and processing. This simplification is based on derivation of the implied reference signals of the SVPWM strategy. The correctness of the proposed algorithm is verified through simulation and experimental results. It is also demonstrated that the proposed simplified algorithm can achieve the same output results as the traditional method with less code length and runtime. [ABSTRACT FROM AUTHOR]

Herein, we introduce a modulation strategy for the synthesis of imine based covalent organic frameworks (COFs) via the condensation of benzene-1,3,5-tricarbaldehyde with 1,3,5-tris (4-aminophenyl) benzene, whereby aniline was adopted as the monofunctional competitor. The introduction of aniline resulted in an enhanced crystallinity, surface area and pore volume, which is beneficial for the enrichment capability of the resulting COFs for the analytes. The optimized COF with the best extraction ability was selected as the solid phase microextraction (SPME) fiber coating for the extraction of polycyclic aromatic hydrocarbons (PAHs) from honey samples. The adsorbed PAHs were then analyzed by gas chromatography with mass spectrometric detection. The merits for the method include: (a) low limits of detection (0.06–0.17 ng/g, S / N = 3), (b) high enrichment factors (290-1566-fold), good reproducibility (relative standard deviations less than 8.4%) and excellent method recoveries for the PAHs (83.0%–116.0%). The enrichment performance of the COFs towards the PAHs could be attributed to the hydrophobic interaction, the high surface area and pore volume of the COF materials. Image 1 • Imine based covalent organic frameworks (TAPB-BTCA-COFs) were constructed through a modulation strategy. • The introduction of the modulator (aniline) led to the enhanced crystallinity and pore property of the COFs. • The TAPB-BTCA-COFs coated SPME fiber possessed good extraction performance toward PAHs. • The fiber was successfully applied to the analysis of PAHs in real honey samples. [ABSTRACT FROM AUTHOR]

In this article, based on the LLC resonant converter fundamental harmonic analysis model, the modulation strategies for LLC resonant converter can be categorized into the following three groups: 1) input voltage fundamental harmonic modulation; 2) resonant tank elements modulation; and 3) secondary equivalent impedance modulation. Operational principles and control diagrams for different modulation strategies are given. Comprehensive comparisons between these modulation strategies in terms of topology complexity, control complexity, and voltage gain range are presented with respect to the same system specifications. The advantages and disadvantages for each modulation strategy are summarized to provide guidance for engineers when analyzing and designing an LLC resonant converter. The hybrid modulation strategies are categorized into different groups based on the specific applications. Brief introductions of these hybrid modulation strategies are presented. Future trends regarding the modulation strategies of LLC resonant converters are presented. [ABSTRACT FROM AUTHOR]

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In this paper, a flexible cascaded multilevel inverter is proposed with a wide operational range. The inverter can change its topology structure to operate in three modes by a bidirectional switch unit. The nine-level or five-level mode of the inverter is adopted to optimize the output waveform when the input power is low. To decrease power losses, the three-level mode of the inverter is adopted to reduce the number of active switch devices when the input power is high. The topology and modulation strategy of the proposed inverter are presented and analyzed. The total losses and current THD of the inverter are calculated. In addition, simulations and experiments are conducted. The obtained simulation and experimental results indicate the correctness and feasibility of the proposed inverter and its modulation strategy. [ABSTRACT FROM AUTHOR]

In this paper, a modified single-carrier and multimodulation sine pulse width modulation (MSCMM-SPWM) is proposed to simplify the implementation of the single-phase asymmetrical neutral-point clamped grid-connected inverter (ANPC-GCI) for the PV generation system application. Furthermore, the expressions of the total switching loss and grid current total harmonic distortion (THD) of ANPC-GCI controlled by the proposed MSCMM-SPWM are derived. Then taking the grid current THD meet the grid-connected standard in the entire operational range as the constraint, an efficiency enhancement scheme for ANPC-GCI based on online adjusting the carrier frequency and the obtained THD expression is proposed. The control configuration of ANPC-GCI, including the proposed MSCMM-SPWM and online efficiency enhancement scheme, is designed. The detailed experimental results verify the correctness and feasibility of the proposed MSCMM-SPWM and the efficiency enhancement scheme. [ABSTRACT FROM AUTHOR]

In this article, an improved modulation strategy for the single-phase single-stage isolated bidirectional ac–dc converter is proposed. The modulation of ac side cycloconverter is based on the unipolar idea to reduce the switching quantity and the ac side current ripple and provide the bidirectional current flow path. The dc side H-bridge converter is driven by the pulsewidth modulation signals cooperatively to speed up the transformer current and thus to eliminate the voltage spike. Furthermore, the power reversion zone (PRZ) of the converter is verified. The action of the proposed modulation strategy in PRZ is analyzed for the first time. It reveals that the reverse current overshoot is caused in ac-to-dc direction and the voltage spike is caused in dc-to-ac direction. An online switching scheme of the proposed modulation strategies in two power directions is proposed to solve these problems. The detailed experimental results verify the correctness and reliability of the proposed modulation strategy. [ABSTRACT FROM AUTHOR]

Industrial applications, e.g., semiconductor manufacturing equipment, require power converters providing high power with high precision and bandwidth. This article presents a three-level flying capacitor resonant pole inverter configuration that combines high output power and high switching frequency with reduced switch voltage stress. A multilevel modulation strategy is applied to minimize conduction losses, which, in addition, guarantees zero-voltage switching (ZVS) for the entire operating range to reduce switching losses. The proposed multilevel converter configuration is compared with an existing two-level configuration by simulation. Increasing the number of voltage levels results in lower total losses and increased linearity of the generated output current. Experimental results acquired with a hardware prototype validate the fast switching of high voltage, proper functioning of the multilevel modulation strategy, and achieving of ZVS. Improvements of the theoretical analysis are presented to compensate for delays in the system and deviating parameter values. Results obtained with a compensated system indicate a relatively high accuracy and linearity of the generated output current of the inverter. [ABSTRACT FROM AUTHOR]

The rise in renewable energy has increased the use of DC/AC converters, which transform the direct current to alternating current. These devices, generally called inverters, are mainly used as an interface between clean energy and the grid. It is estimated that 21% of the global electricity generation capacity from renewable sources is supplied by photovoltaic systems. In these systems, a transformer to ensure grid isolation is used. Nevertheless, the transformer makes the system expensive, heavy, bulky and reduces its efficiency. Therefore, transformerless schemes are used to eliminate the mentioned disadvantages. One of the main drawbacks of transformerless topologies is the presence of a leakage current between the physical earth of the grid and the parasitic capacitances of the photovoltaic module terminals. The leakage current depends on the value of the parasitic capacitances of the panel and the common-mode voltage. At the same time, the common-mode voltage depends on the modulation strategy used. Therefore, by the manipulation of the modulation technique, is accomplished a decrease in the leakage current. However, the connection standards for photovoltaic inverters establish a maximum total harmonic distortion of 5%. In this paper an analysis of the common-mode voltage and its influence on the value of the leakage current is described. The main topologies and strategies used to reduce the leakage current in transformerless schemes are summarized, highlighting advantages and disadvantages and establishing points of comparison with similar topologies. A comparative table with the most important aspects of each converter is shown based on number of components, modes of operation, type of modulation strategy used, and the leakage current value obtained. It is important to mention that analyzed topologies present a variation of the leakage current between 0 to 180 mA. Finally, the trends, problems, and researches on transformerless grid-connected PV systems are discussed. [ABSTRACT FROM AUTHOR]

Smart transformers (STs) are challenged by high-reliability requirements. Particularly, modular STs consist of a large number of power semiconductors, and unevenly distributed thermal stress results in different remaining useful lifetimes of the devices in the different building blocks. This problem can be addressed with discontinuous modulation for the medium-voltage-side converter, but results in a coupled thermal stress with the isolated dc–dc cells. For overcoming this drawback, this article proposes an advanced discontinuous modulation, which enables to manipulate thermal stress in different cells independently. The algorithm is analyzed with respect to its capability in thermal stress manipulation and validated experimentally with junction temperature measurements. In addition, this article investigates the impact of the algorithm on the overall system's efficiency as well as potential lifetime of the power semiconductors in the different building blocks. [ABSTRACT FROM AUTHOR]

This paper proposes a single-source switched-capacitor multilevel inverter for magnetic coupling wireless power transfer (MC-WPT) systems. The proposed inverter consists of one DC source, two half bridges, and novel extensible I-type switched-capacitor modules. It can generate a staircase waveform voltage with higher amplitude and lower total harmonic distortion, and the voltage stress of all power switches is equal to the DC input voltage, so high output power can be obtained by power switches with low voltage capacity. Compared with the existing multilevel inverters, the proposed inverter requires a less number of power switches and energy storage components to generate the same number of voltage levels, which means better voltage boost ability. Moreover, it can achieve self-voltage balancing of switched capacitors easily without balancing circuit or control algorithm. The topology, operating principle, output voltage, and self-voltage balancing ability of the proposed inverter are analyzed, and the comparison with the existing multilevel inverters is presented. The modulation strategy and value of the switched capacitor are designed, and the soft switching state and power loss are analyzed and calculated. Finally, an experimental setup of a 1-kW MC-WPT system is implemented to verify the correctness of the theoretical analysis and the feasibility and superiority of the proposed inverter. [ABSTRACT FROM AUTHOR]

The battery is the only power source of full electric vehicles, and the converter plays a key role in power and signal conversion; therefore, the stability and reliability of the converter determine the performance of the whole vehicle system. In order to improve the overall performance of the converter and optimize the function of the ID-NPC (improved diode neutral-point-clamped) topology with power allocation, the two-level topology is improved, and it is also a part of the ID-NPC topology. Based on the ID-NPC topology, the converter level can switch according to the proposed three-level and two-level modulation conversion strategies, which extends the fault-tolerant function of the converter. Finally, a simulation and experimental platform is built to verify the function of the improved topology and the feasibility of the proposed modulation strategy.

Using electric motors with a number of phases greater than three present some advantages over conventional three-phase machines: higher reliability, reduced power per phase, increased torque density, and reduced torque pulsations. As the number of phases increases, the complexity of the modulation also increases due to a larger number of switching vectors and harmonic planes. A nine-phase inverter implies 512 switching vectors in each one of its four harmonic planes. In this article, a modulation technique for a nine-phase inverter based on a subset of the voltage vectors that yields a reduced number of on/off transitions in a switching period is shown. The resulting harmonics and their effects in multiphase machines are analyzed. Third harmonic injection is considered from the perspective of both torque improvement and dc bus voltage utilization. Simulation, finite element, and experimental results are presented to support the authors’ conclusions. [ABSTRACT FROM AUTHOR]