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Electrolytic capacitorless Vienna rectifiers have many advantages, such as longer lifetime and higher power density. However, the reduced dc-link capacitance aggravates the voltage stress due to the neutral point (NP) fluctuation. In this article, a hybrid modulation strategy combining the modulations of redundant vector and compression vector is proposed, which can realize the NP voltage balance for electrolytic capacitorless Vienna rectifiers. On the basis of analyzing the limitation of NP-balance capability of conventional space vector pulsewidth modulation (PWM) strategy in the region of high modulation index, the negative influence of reduced capacitance on the NP fluctuation and the input current harmonics is revealed. To suppress the NP fluctuation, the compression coefficient is introduced to redistribute the duty cycles of voltage vector, which can reduce the negative effect of medium vector on the NP voltage. In addition, the phase voltage error is modeled to reduce the input current harmonics with the appropriate adjustment factor. The implementation of the proposed strategy is realized by the equivalent carrier-based PWM, which can avoid the sector judgment and angle calculation. By using the proposed strategy, the NP voltage balance and the input current harmonics reduction can be realized simultaneously. The effectiveness of the proposed strategy is verified on an electrolytic capacitorless Vienna rectifier platform. [ABSTRACT FROM AUTHOR]

This letter proposes a switched capacitor (SC)-based continuously adjustable modular bidirectional dc–dc converter. The structure of the proposed converter consists of three types of modules, series–parallel SC converter module, regulating module, and resonant SC converters module. A basic configuration of three modules working in buck operating mode is analyzed in detail. The boost mode operation is symmetrical to the buck mode. The regulation module provides all regulation capability, and the other two modules operate at fixed duty cycle and provide the main conversion ratio. A prototype of the basic configuration was built to verify the theory. The peak efficiency of the prototype is 97.15%. [ABSTRACT FROM AUTHOR]

In this article, a high-performance modified Y-source dc–dc converter is proposed. Comparing with traditional Y-source dc–dc converter, the proposed converter can achieve soft switching characteristics. Due to the discontinuous conduction mode operation of one of the coupled inductor windings and the resonant cell constructed by switch parasitic capacitor, the switch can operate in zero voltage switching (ZVS) and diodes realize zero current switching. Also, the voltage gain of the proposed converter is greatly improved. Meanwhile, the control strategy of hybrid pulsewidth modulation and PFM is adopted to guarantee the ZVS operation within a wide range. A 160 W experimental prototype based on planar coupled inductor is built to verify theoretical analysis and efficiency is up to 94.45% under full load condition. [ABSTRACT FROM AUTHOR]

The nonlinearity of the voltage source inverter (VSI) leads to the error between output voltage and reference voltage, and causes the phase current harmonics. It is necessary to compensate its influence in the fields such as parameter identification, sensorless control, and servo drives. In this article, an industrial solution for VSI nonlinear compensation method based on lookup table (LUT) is introduced. The characteristics of semiconductor devices, equivalent dead-time and influence of parasitic capacitance effects are calculated quantitatively though injecting increase and decrease current during self-commissioning process. The critical current value for parasitic capacitor and the variation of equivalent dead time are verified through different distorted voltage curves. Considering dc-link voltage variation is irresistible for industrial products, 3-D linear interpolation is adopted to compensate the variation of VSI nonlinearity under different voltage conditions. Proposed LUT method does not require VSI datasheet and complicated calculation formula during implementation. Experiments are carried out on a commercial permanent magnet synchronous motor drive system to verify the proposed LUT method. [ABSTRACT FROM AUTHOR]

Inthis article, a two-phase series capacitor dual-path hybrid dc–dc converter with the step-down ratio of less than 1/6 is proposed for the first time. In this converter, the output current is divided into capacitance- and inductance-path, so the average value and ripple of inductance current are reduced. On the same time, the conduction loss caused by inductance equivalent series resistance (ESR) is also reduced. The addition of series capacitor leads to desirable characteristics, including lower switching stress, switching loss, parasitic output capacitance loss on mosfet, automatic phase current balancing, duty ratio extension, etc. A 120 W prototype has been designed to demonstrate theoretical analysis. Obtained efficiency was up to 93.18% at full load. Experimental results show good agreement with theoretical analysis and high feasibility of proposed converters. [ABSTRACT FROM AUTHOR]

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]

An integrated zero common-mode voltage (ZCMV) modulation algorithm is developed in this article for dual-parallel neutral-point-clamped (NPC) inverters treated as an integrated system. While the conventional methods achieve CMV elimination with the cost of worse harmonic performance, the proposed method guarantees a ZCMV and better current quality simultaneously by taking advantage of the extra space vectors provided by paralleling. Specially designed switching sequences are developed to maintain a balanced neutral point of dc bus and keep the averaged value of the circulating current to be zero, ensuring the normal function of parallel NPC inverters. In addition, although the switching sequence design is complicated, a simple approach is proposed and implemented on a commonly used digital signal processor. A laboratory prototype is developed to test the system performance under steady-state conditions and dynamic process in grid-connected operation. Compared with the conventional ZCMV modulation, experimental results verify the effectiveness of the integrated modulation in eliminating the CMV, in addition to the dramatically reduced output current distortion. [ABSTRACT FROM AUTHOR]

The extensive application of vector phase shift modulation method in permanent magnet synchronous motor drive systems with single dc-link current sensor results in obvious current ripple in the low-speed region. The patterns of these ripples vary greatly in different sectors, leading to nonnegligible phase current reconstruction errors. In this article, an estimation of the local average current change rate (ELAC2R) based reconstruction error suppression method within the switching cycle is proposed to resolve this problem. By comparing the actual and the ideal sampling points, the increase of current ripple and the reconstruction error caused by the combination of the vector phase shift and the single current sensor sampling in the low-speed region are modelled and analyzed. Then according to equivalent modelling of the current ripple between the ideal and the actual sampling points, the more accurate phase current information can be quickly obtained based on the sampling value. The compensation process is significantly simplified and the computation burden of the processor is reduced. Experimental results show that the performance of current reconstruction can be improved effectively with less harmonic content with the proposed method. [ABSTRACT FROM AUTHOR]

In this article, a 10 MHz dc/dc converter based on three-dimensional air core transformer with zero-phase difference synchronous driving signals is designed. By using the characteristics of no leakage inductance in the inner winding of the nested toroidal air core transformer, the phase difference between the output voltage of the inverter and the input voltage of the rectifier can be regarded as zero, so that the rectifier and the inverter can use the same driving signal, which simplifies the control of the synchronous rectifier switches, and realizes the reliable and efficient synchronous rectification control at 10 MHz. The prototypes with primary and secondary compensation are proposed and the experimental results verify the feasibility of the proposed control method and numerical design method. [ABSTRACT FROM AUTHOR]

Many reduced common mode voltage (CMV) modulation methods have been proposed for three-level inverters. However, most of them suffer from large current distortion because only part of the available base vectors is utilized. The interleaved paralleling can reduce both CMV and the output current distortion, though the CMV reduction is limited and large zero-sequence circulating current (ZSCC) is inevitably caused by the phase-shifted carriers. To further reduce the CMV while maintaining smaller current distortion and ZSCC, a five-level reduced CMV (RCMV) modulation method is proposed in this article, which treats the parallel inverters as a whole. Theoretical analysis reveals that the integrated modulation provides additional base vectors that contribute to smaller total harmonic distortion (THD) of the current, and the selected vectors ensure the nearest-three-vector synthesis and half-reduced CMV. The switching sequences design and neutral point balancing strategy are also developed for dual-parallel three-level inverters, ensuring that the average circulating current is zero and the neutral point voltage is balanced, which are both critical to the proper operation of parallel inverters. Superior performance in terms of CMV, THD, and ZSCC provided by the proposed method in comparison with conventional modulation is verified by comprehensive simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this article, a soft-switching transformer-less step-down converter based on a resonant current balance module is proposed. An LED driver is taken as an example of the analysis and design of the converter. The converter is made up of a stacked half-bridge, resonant current balance modules, and pairs of light-emitting diode (LED) strings. The resonant current balance modules allow the proposed converter to realize automatic current sharing, soft switching, and extending to a 1/N converter. The proposed converter can operate in discontinuous conduction mode (DCM) or continuous conduction mode (CCM) mode by choosing different operation frequencies, and achieve zero current switching or zero voltage switching (ZVS), respectively. Also, by using frequency doubling technique in the half-bridge, the switching losses are reduced by half under the same conditions. A 15.8-W experimental prototype with 100 V input voltage and 25 V output voltage has been implemented in the laboratory, verifying the feasibility of the soft-switching transformer-less step-down converter. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) is regarded as an emerging topology in medium-voltage (MV) variable-speed motor drive applications, particularly for driving fan-/pump-like loads. The main challenge is the large capacitor voltage ripple of MMC at low speed with high starting torque. In this brief, a simple and cost-effective modified MMC topology is introduced, which can provide high toque to motor during the zero/low frequency. The topology is particularly suitable for fan-/pump-like loads. Circuit structure and operation principle of this modified topology is explained, and the control schemes are also developed. Validity and effectiveness of this topology are verified by experimental results. [ABSTRACT FROM AUTHOR]

Bipolar LVdc distribution is a promising solution for better integration of renewables and enhancement of system efficiency and reliability, but it also faces the challenge of pole voltage imbalance. By simple modifications of the bidirectional CLLC dc/dc converter, this article presents a dc/dc converter with integrated pole voltage balance capability. The converter presents less number of semiconductors, smaller overall footprint, and lower power loss compared to the employment of additional pole voltage balancers. Operating principle of this dc/dc converter and its inherent pole voltage balancing capability are explained, while further control scheme is also developed to compensate the small pole voltage difference caused by the dead time effect. Simulation results with 150 kW/±375 V bipolar output demonstrate the effectiveness of the converter, and the experimental results from a 500 W/±50 V downscaled prototype further prove the proposed concept. [ABSTRACT FROM AUTHOR]

Because of the time-sharing sampling logic, the three-phase currents reconstructed by single dc-link shunt present significant errors in the permanent magnet synchronous motor drives. A traceback-prediction current correction method for sampled currents is proposed in this article to eliminate the reconstruction errors. According to the analysis of time-sharing sampling errors, the concept of equivalent current change rate during one pulsewidth modulation (PWM) period is introduced, and the phase current characteristic model based on state observer is established. Both the equivalent and instantaneous current change rates can be obtained by the observer-based calculation method. In order to improve the current reconstruction precision, the ultimate values of three-phase currents can be predicted by adopting the proposed traceback-prediction current correction method, which does not require major computation and is easy to implement with no restrictions on the PWM strategy. The effectiveness of the proposed method is verified by experimental results. [ABSTRACT FROM AUTHOR]

This article presents a dc solid state transformer based on three-level power module (PM) (TL-DCSST) for interconnection of medium-voltage dc (MVdc) and low-voltage dc distribution system. The proposed TL-DCSST adopts the low-voltage insulated-gate bipolar transistor (IGBTs) with excellent switching characteristics to build medium voltage PM and reduces the number of medium frequency transformer (MFT). This topology features inherent antibias mechanism for MFTs on the primary side, which saves the resonant capacitor at primary side. Meanwhile, the active front end is integrated to realize voltage and power regulation, low voltage ride-through and DC fault handling for MVdc side. In this article, the topology, operation principle, interleaving modulation, circuit parameter design, and control schemes are presented and analyzed comprehensively. At last, a prototype rated at 7 kW has been built and tested, and the experimental results verify effectiveness of the proposed TL-DCSST. [ABSTRACT FROM AUTHOR]

With the rapid development of voltage source converter-based high-voltage direct current (HVdc) transmission, it is an irresistible trend that HVdc grid will come into being. High-voltage and high-power dc/dc converters will serve as dc transformers in HVdc grid to interconnect dc lines with different voltage ratings. This article proposes a monopolar symmetrical dc/dc converter which is composed of cascaded half-bridge submodules and series-connected insulated-gate bipolar transistors. This hybrid topology features low capital costs, high efficiency, small footprint, and bidirectional power transfer capability. Operation principle, parameter design, and the control strategies of this topology are introduced. A 480-MW, ±500 kV/±160 kV monopolar symmetrical dc/dc converter is simulated to verify its performance and evaluate the efficiency. In addition, a downscaled prototype rated at 2.4 kW, ±300 V/±100 V has been built and tested. Experimental results further validate the effectiveness of the proposed dc/dc converter. [ABSTRACT FROM AUTHOR]

In this article, a novel 20-MHz high-frequency high-performance dc–dc resonant converter is analyzed, which owns the characteristics of soft-switching, low voltage stress, and small volume. The numerical analysis is conducted in time domain and the resonant parameters can be accurately calculated based on the corresponding expressions. A full resonant rectifier stage is adopted without using choke inductors, and the value and volume of inductors can be greatly reduced. A 12-V input, 5 V/5 W output prototype is proposed in the laboratory and the experimental results verify the feasibility of the proposed converter and numerical design methodology. [ABSTRACT FROM AUTHOR]

A novel discontinuous conduction mode (DCM) soft-switched single ended primary inductor converter (SEPIC)-based high-frequency converter is presented in this article with the advantages of high voltage gain and low voltage stress. In order to achieve higher voltage gain, it integrates a switched inductor with a coupled inductor–based modified SEPIC converter, and a resonant cell is built with integration of a resonant capacitor, which enables the switches to work under zero voltage switching (ZVS). Therefore, the working principle is changed and better performance is obtained. The proposed converter can operate in both continuous conduction mode (CCM) and DCM, but ZVS can only be achieved in the discontinuous mode; hence, DCM is more suitable for high-frequency applications. Mode analysis, parameter design, and boundary of the two working modes are all presented in detail. For higher efficiency, a 500-kHz/54-W DCM prototype with 15 voltage gain has been designed to demonstrate theoretical analysis. Obtained efficiency was up to 93.4% at full load. Experimental results show good accordance with theoretical analysis. [ABSTRACT FROM AUTHOR]

Recently, remarkable progress has been made in the voltage-source-converter-based high-voltage direct current (HVdc) transmissions. For the upcoming need to interconnect multiple dc transmission lines with different voltage levels, high-voltage and large power dc/dc converters are necessary. This article investigates a nonisolated bidirectional dc/dc converter that is composed by cascaded half-bridge submodules, series-connected diodes, and mechanical disconnectors. This hybrid topology presents very attractive features, such as low cost, high efficiency, and light weight. Operation principle, parameter design, and dedicated control strategies are developed. Simulation of a 150-MW, 200 kV/300 kV dc/dc converter has been performed to verify its performance and evaluate the efficiency. Moreover, a downscaled three-phase prototype rated at 500 V/300 V 4.5 kW has been built and tested. The experimental results further confirm the effectiveness of the proposed dc/dc converter. [ABSTRACT FROM AUTHOR]

In this paper, many impedance-source inverters with coupled inductors have been investigated to obtain a high step-up boost ratio. However, the leakage inductors in these topologies induce great voltage spikes at the dc link, which will increase the voltage stress of switches. Thus, the power level of inverters is limited. Furthermore, the efficiency of the inverters can be degraded by the losses associated with leakage inductors. To address abovementioned issues, this paper proposes a family of low-spike high-efficiency Y-source inverters. The proposed inverters have the ability of eliminating voltage spikes at the dc link and recycling the leakage energy via the additional diode and capacitor. In order to show the excellent characteristics of the proposed topologies, this paper compares the performances of the proposed inverters and the improved-Y-source inverter in many aspects. Simulation and experimental results have verified the abilities of the proposed inverters. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) power electronic devices feature the advantages of fast switching speed, low conduction loss, and reliable operation in high temperature environment, etc. Due to the differences of parasitic parameters and threshold voltage between SiC mosfets and Si mosfets, crosstalk problem is easy to be triggered when SiC mosfets are applied to bridge topologies. In this paper, the crosstalk effect with different parasitic parameters of SiC mosfets is firstly analyzed, and then an improved active crosstalk suppression method for high-speed SiC mosfets is proposed. By using the proposed method, when the crosstalk occurs, the crosstalk voltage will be decreased by reducing the equivalent gate resistance and increasing the equivalent gate-source capacitance in an active way. Consequently, the crosstalk problem can be suppressed without affecting the switching speed. To verify the effectiveness of the proposed method, a prototype of a buck–boost converter is built and the proposed modified gate driver is applied to the half-bridge topology. Comparative experimental study is conducted and the crosstalk voltage is analyzed. The experimental results verify that effective crosstalk suppression is achieved. [ABSTRACT FROM AUTHOR]

With the rapid development of photovoltaic and fuel cell stacks, high voltage gain converters are urgently demanded. Conventional boost is limited by the exaggerated duty cycle, it is impossible to obtain a high voltage gain while ensuring efficiency. Therefore, a zero-voltage switching (ZVS)-modified SEPIC converter that combines a voltage multiplier cell with traditional SEPIC is proposed in this paper. With detailed parameters design process, this presented converter works at zero voltage switching (ZVS), while obtaining high voltage gain without extremely high duty cycle. Besides, voltage stress is also reduced and low-voltage component with lower parasitic parameters can be used, thus efficiency is maintained. In order to further improve the power density, an integrated inductor scheme is adopted in this paper without changing intrinsic working states of the two inductors. A 36-W prototype is built, and experiments are conducted to verify the advantages of the proposed converter. The efficiency is up to 91.5% at full load. [ABSTRACT FROM AUTHOR]

With the increase in demand for high voltage gain characteristics, traditional Boost circuit is no longer suitable because of the extreme duty ratio. In this brief, with the integration of two diodes, three capacitors, and a transformer, a 1 MHz transformer-based modified SEPIC circuit is presented. Planer magnetic components are adopted, and therefore the core volume does not increase. Higher voltage gain and lower voltage stress are obtained simultaneously. Moreover, zero voltage switching is achieved at the same time, which reduces the switching loss caused by the increment of switching frequency. The operational principle and parameter design process are introduced in detail. An 80 W prototype is designed to demonstrate theoretical analysis. Obtained efficiency was up to 92.6% at full load. [ABSTRACT FROM AUTHOR]

This paper presents a novel integrated-stage light-emitting diode (LED) driver based on Flyback and resonant converters. The Flyback converter realizes power factor correction in the discontinuous conduction mode. The resonant converter is operated as a dc–dc converter to support the LED loads. Moreover, the resonant converter can clearly decrease the drain–source voltage of the active switch and exhibits zero-voltage-switch characteristics. Therefore, a cost-effective MOSFET can be chosen as the main control component that can decrease the cost of the whole system. Compared to a single-active-switch converter (such as Class-E converter), the number of passive components in the resonant converter can be limited to four. Therefore, the power density of the system can be improved drastically. In this paper, a 100-W prototype is presented under the experimental condition to validate the proposed integrated-stage LED driver. [ABSTRACT FROM AUTHOR]

In ac motor drives, the fixed-frequency harmonic components of output voltage and current from the inverter with fixed-frequency pulsewidth modulation usually lead to electromagnetic interference (EMI). The spread spectrum clock generation (SSCG) is a widely used solution for this problem. Adjusting the switching frequency to reduce EMI is one kind of practicable scheme among SSCG methods. How to design an optimal or suitable modulation profile is a research emphasis of scholars and has been discussed in depth in many literatures. However, apart from the modulation profile, the mode and quality of carrier are also important and can be improved. In most frequency modulation methods, due to the limitation of the conventional carrier generation mode, the implementation of the new frequency instruction has to wait for the termination of the last switching period. In order to eliminate the waiting state and design a simpler algorithm, this paper has proposed a wait-free phase-continuous carrier frequency modulation (WPCFM) strategy by combining the direct digital frequency synthesizer theory and proper temporal planning of control interruptions. Besides, a theoretical analysis of WPCFM, including quantization error, frequency jitter, phase delay, and voltage distortion, has been finished. Moreover, compared with conventional methods, a more convenient, feasible, and simpler field-programmable gate array based algorithm implementation method and the control structure of WPCFM are also introduced. The analysis shows that, although WPCFM causes a slight increase of the current ripple, it can solve the partial frequency nonuniform distribution problem of the conventional method, and it has a potential value of applications in the wide band gap motor drive systems. The effectiveness of the WPCFM is verified by several sets of EMI reduction experiments where classical periodic carrier frequency modulations are applied. [ABSTRACT FROM AUTHOR]

A high-frequency high voltage gain discontinuous conduction mode coupled-inductor boost LED driver based on planar component is presented in this paper. GaN switch is adopted with lower conducting resistance and higher switching speed. Zero voltage switching (ZVS) is achieved at the same time to reduce high switching loss caused by high switching frequency. Compared with the previous work, the voltage gain is higher and efficiency is higher because of ZVS. This paper focuses on high efficiency; therefore, resonant gate driver is adopted and efficiency is increased by 0.6%. In terms of the coupled-inductor, planar component is used and parameter optimization is also proposed to realize lower loss, including wingding loss and fringing loss caused by the air gap. A 500 kHz 36 W prototype has been designed to demonstrate theoretical analysis. In addition, comparison of drive loss between the resonant gate driver used in this paper and conventional driver implemented by Si8271 is made, revealing advantages of the resonant driver. Obtained efficiency was up to 92.1% at full load. [ABSTRACT FROM AUTHOR]

In distributed generation, grid-connected and islanded modes are essential, but usually they have different control cores to satisfy their respective control targets. Transferring between the cores may therefore lead to prominent disturbances, if the cores are complex and noticeably different in structures. To introduce seamlessness, some techniques have been recommended, but they usually lack unification of control blocks for the front dc–dc converter and rear dc–ac inverter. Moreover, when connected to the grid, some seamless techniques do not control the grid current directly. Hence, its dynamics may be slow, in addition to distortion caused by grid-voltage harmonics. When islanded, most techniques also use two control loops to regulate a drooped voltage across local loads. This double-loop structure works fine, but it has more state variables to change during a transfer of modes, which may not be as seamless. An alternative technique has thus been proposed here, whose purpose is to identify a simple unified control core, which will remain unchanged during the mode transfer. The transfer may then be viewed as a normal change of power reference, instead of an internal change of control structure. Hence, seamless operation may be ensured, as it is tested in simulations and experiments. These tests have additionally shown that the proposed scheme can regulate the grid current directly when connected to the grid, without compromising the droop-voltage regulation when islanded. [ABSTRACT FROM AUTHOR]

This paper proposes a high-frequency isolated dc/dc converter, whose switching frequency is 20 MHz. Meanwhile, the switch voltage stress is reduced based on optimal switch impedance. In the proposed converter, the switch can operate in ZVS condition, which can help to reduce the switching loss. A mathematical model of the proposed high frequency converter is built, which provides an effective design method for the system parameters. Meanwhile, the design method for PCB air-core transformer has been proposed and depicted. To verify the feasibility of the proposed converter and mathematic model, a 10 W prototype is built. [ABSTRACT FROM AUTHOR]

In this paper, an isolated high-frequency converter with optimal switch impedance is proposed, which can achieve soft-switching characteristics and a low switch voltage stress. Meanwhile, the topology makes full use of the parasitic components of the transformer, which can reduce the number of system components and improve the system efficiency. The detailed design method of the proposed converter is analyzed. Simultaneously, an air core printed circuit board (PCB) transformer is employed to eliminate the core loss and reduce the vertical space. On the basis of the mathematical analysis, the transformer parameters can be effectively designed. A 20-MHz prototype based on the proposed topology is built. The experimental results verify the advantages of the proposed converter and the corresponding design method. [ABSTRACT FROM AUTHOR]

Impedance-source inverters using coupled inductors have been investigated as alternatives for providing high step-up voltages. However, leakage inductances of the coupled inductors have commonly led to lower overall effectiveness, in addition to generating high dc-link voltage spikes. The latter raises voltage stresses of switches, which in turn, may reduce the power levels of the inverters. A high step-up Y-source inverter has therefore been proposed in this paper to provide a high boost with a smooth dc-link voltage ensured by proper recycling of the leakage energy. These features have been verified by comparing simulation and experimental results of an existing Y-source and the proposed inverters. Factors compared are their respective boost ratios, voltage stresses, current stresses, and dc-link voltage spikes. [ABSTRACT FROM AUTHOR]

In recent years, significant progress has been made in HVdc transmission, particularly the voltage-source-converter technology using modular multilevel converters. There is increasing demand to develop high-power dc/dc converters to interconnect HVdc systems with different voltage levels. In this paper, a novel hybrid dc/dc converter topology is proposed by the combination of a new three-switch submodule (SM) circuit and series-connected thyristors and diodes. This topology presents less amount of semiconductors, very attractive capital costs, small footprint, and low power losses. Operating principles of this new three-switch SM and the dc/dc converter are explained, while the modulation and control schemes are also developed. The validity of the proposed topology is verified by simulation results based on a 150 MW, 200 kV/300 kV dc/dc converter. Efficiency estimates indicate that this topology could have power losses as low as 0.3% rated power. A scaled-down prototype has also been built and tested to confirm its effectiveness. [ABSTRACT FROM AUTHOR]

In this paper, a high step up converter consisting of an integrated quadratic-boost converter and a voltage doubler is proposed. The integration of the quadratic-boost converter makes the system easier to lift up its voltage gain through slightly increasing the duty ratio of the single switch. The voltage doubler further increases the voltage gain of the system as the turn ratio rises. The voltage stresses on the switch and the diodes are decreased for such cascaded topology. Different operation modes are analyzed and mathematical analysis of the converter is presented in detail. The leakage inductance contributes to realizing zero current switching of the diodes in the second boost stage and the doubler and the energy can be recycled to the load. A 38-W prototype is built to work as a vehicle LED driver. Experiments are conducted to verify the advantages of the proposed converter and the efficiency is 90% at the nominal operating point. [ABSTRACT FROM AUTHOR]

A 1-MHz-modified single-ended primary-inductor converter (SEPIC) circuit is presented in this paper as an LED driver for automotive headlights. On the basis of traditional SEPIC, only a diode and two capacitors are added; therefore, the circuit structure is relatively simple and the volume is relatively small. High step-up capability is obtained with moderate duty cycle. Compared with traditional step-up circuit such as boost, low-voltage stress is gained which is beneficial to device selection. Zero-voltage switching is achieved at the same time to reduce switching loss. Planar inductors are used with the advantages of low profile and good thermal characteristic. Operational principle and parameters design process are introduced in detail. A 36-W prototype has been designed to demonstrate theoretical analysis. Obtained efficiency was up to 90.91% at full load. [ABSTRACT FROM AUTHOR]

A high-performance impedance-source converter utilizing switched inductor is proposed in this paper, which can be adopted in the applications demanding high-voltage conversion. The proposed converter not only retains the advantage of quasi-Z-source of sharing common ground between the input and output but also possesses the superiorities of enhanced boost ability and lower stresses as well as higher efficiency. Mathematical analysis of the converter and its performance comparison with other converters are presented in detail. Finally, a 100 W prototype is built and the experimental results are provided to verify the feasibility of the proposed converter. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) represent an emerging topology in medium-voltage (MV) and high-voltage applications. But for MV variable-speed motor drives, the MMC faces the challenge of large capacitor voltage ripple at low speeds. Delightfully, a hybrid MMC (HMMC) has proved to be potential in MV motor drives, since this topology has a lower capacitor voltage ripple and does not introduce any common voltage to the motor. This paper proposed a method to decrease the average capacitor voltage of the HMMC, which can effectively drive the motor at very low speeds without significantly increasing the submodule (SM) capacitance. Moreover, the selection of average capacitor voltage and the dimension of the SM capacitance are presented. Simulation and experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Although high-frequency circulating current exists in parallel-operated inverters, it has not attracted as much attention as low-frequency circulating current, and thus has not been analyzed in detail previously. In this paper, a mathematical model and analysis are presented, which reveal the spectrum components and their changing trends of the circulating currents caused by carrier phase differences. The impact of carrier phase difference on high-frequency circulating current is also analyzed and verified. A closed-loop control scheme is proposed to suppress the switching frequency circulating current caused by carrier phase difference. In addition, the deadbeat and closed-loop control are combined to suppress the low- and high-frequency circulating currents simultaneously, to improve the overall performance of circulating current suppression. The effectiveness of the proposed scheme is verified by the simulation and experimental results acquired from a laboratory platform. [ABSTRACT FROM AUTHOR]

By using coupled inductors, impedance-source inverters can greatly increase their voltage step-up abilities at the expense of high voltage spikes at their dc-links due to leakage inductances. These voltage spikes can then cause damages and greater power losses. Therefore, to better clamp their dc-link voltages, various absorbing circuits have been proposed in this letter for forming a unique family of impedance-source inverters with even higher gains. The abilities of these inverters in clamping their dc-link voltages have been verified by experimental results presented at the end of the letter. [ABSTRACT FROM AUTHOR]

This paper presents a single-stage light-emitting diode (LED) driver based on a bridgeless power factor correction (PFC) converter and a half-bridge CLCL resonant converter for street lighting applications. The proposed single-stage topology integrates the PFC converter and the CLCL resonant converter by sharing active power switches. The bridgeless PFC converter adopts two buck–boost circuits operating in discontinuous-conduction mode to achieve input-current shaping. It uses two diodes instead of a rectifier bridge to reduce the power loss caused by the diodes. Owing to its superior soft-switching characteristics, the CLCL resonant converter is used. The proposed LED driver has superior features, such as high efficiency, near unity power factor, low total harmonic distortion, and relatively few diodes. A 100-W lab prototype is successfully implemented, and the experimental results verify the effectiveness and feasibility of the proposed LED driver. [ABSTRACT FROM AUTHOR]

With the development of high frequency converters, driving circuits have gained more and more attention. Self-driven methods can effectively simplify system design and reduce components’ number. A basic self-driven circuit can be achieved by adding a series resonant inductor at the switch gate; however the losses of driving circuit are high. To reduce the corresponding losses, a high efficiency self-driven network with an additional parallel branch is proposed, which can significantly improve the system efficiency. A 13 MHz prototype is built to verify the feasibility of the proposed self-driven circuit. The system efficiency can be improved from 80% to 83.9%. [ABSTRACT FROM AUTHOR]

A traditional flyback LED driver is limited by its low performance, which usually does not meet the power factor (PF) and total harmonic distortion requirements according to Energy Star or IEC61000-3-2. The control loop from the secondary side to the primary side has low reliability and employs more components, which reduces the power density of the system and increases the cost. In this brief, based on single-stage single ended primary inductor converter (SEPIC) and flyback converter, a primary-side-regulated LED driver is proposed to improve the performance of the system. Working in DCM, the SEPIC circuit realizes the PF correction naturally. For the flyback converter, the proposed primary-side-regulated method improves the power density and guarantees accurate control of the output current. A 100-W prototype based on SEPIC-flyback was built to verify the analysis and the experimental results coincided with the analysis results satisfactorily. [ABSTRACT FROM PUBLISHER]

A two-stage quasi-resonant LED driver with a digital control method is proposed in this paper. The first stage of this converter is a boost circuit with a power factor correction function, and the second stage is a dual-buck circuit that works in a quasi-resonant zero voltage switching state. Because of the soft-switching characteristics of the converter, switching losses are reduced and efficiency is significantly improved. A digital control method is adopted to detect the peak value of inductor current and enhance system reliability. Moreover, because LEDs are always driven by a current source, a current loop is designed to maintain constant output current. IRS2104 is chosen as the drive chip and the microcontroller is AT90PWM216, which can improve the quality of the drive signals. The output of the converter is a square wave that drives two branches of antiparallel LEDs. A 60-W prototype was designed to demonstrate the theoretical analysis. The obtained power factor was as high as 0.987 and the efficiency reached 92.3%. [ABSTRACT FROM PUBLISHER]

A single-stage light-emitting diode (LED) driver has been developed integrating a single-ended primary-inductor converter with a half-bridge LLC resonant converter. The proposed topology reduces system's cost, enhancing reliability. Because the LLC resonant part maintains soft-switching characteristics, switching losses are relatively low. Due to careful parameters selection, the system bus voltage can be kept low as needed in high-power LED drive designs. Some experiments using a 100-W prototype were performed to validate theoretical analysis. The obtained power factor was as high as 0.99, and due to soft-switching operations efficiency was up to 92% at full load. [ABSTRACT FROM PUBLISHER]

Modular multilevel converters (MMC) have revolutionized the voltage-sourced converter-based high-voltage direct current transmission, but not yet got widespread application in medium-voltage variable-speed motor drives, because of the large capacitor voltage ripples at low motor speeds. In this paper, a novel hybrid MMC topology is introduced, which significantly reduces the voltage ripple of capacitors, particularly at low motor speeds. Moreover, this topology does not introduce any motor common-mode voltage; as a result, there are no insulation and bearing current problems. Additionally, the current stress can remain at rated value throughout the whole speed range; thus, no device needs to be oversized and converter efficiency can be ensured. Operating principle of this hybrid topology is explained, and control schemes are also developed. Validity and performance of the proposed topology are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

A novel high-power-factor single-stage single-switch light-emitting diodes (LEDs) driver for street lighting system is proposed in this paper. By integrating the single-ended primary-inductor converter (SEPIC) power factor correction circuit and Class-E resonant dc/dc converter, the proposed converter exhibits extreme simplicity and high reliability, as there is only one active power switch. The LED driver could achieve nearly a unit power factor by operating the SEPIC circuit at discontinuous conduction mode. With careful parameters design of a single Class-E resonant converter, the proposed converter can achieve soft-switching characteristics, which could significantly reduce the switching losses and greatly improve the system efficiency. Operational principle, analytical results, and design considerations at 100 kHz are presented, and a 100-W laboratory prototype is proposed to verify the theoretical analysis, whose efficiency is as high as 91.2% in full-load state under 110 VAC input. [ABSTRACT FROM AUTHOR]

This paper proposes a single-stage single-switch light-emitting diode (LED) driver that integrates a buck–boost circuit with a Class-E resonant converter by sharing single-switch device. The buck–boost circuit, working as a power-factor correction (PFC) stage, operates in the discontinuous conduction mode (DCM) to shape the input current. The Class-E converter steps down the voltage to drive the LED. For specific component parameters, the Class-E converter can achieve soft-switching on the power switch and two rectifier diodes, and reduce switch losses at high frequencies. Electrolytic capacitors are used in the proposed converter to achieve a lower cost, but the system reliability decreases. To overcome this disadvantage, film capacitors can be used, but the current ripple increases. Neglecting the cost, multilayered film capacitors are the best option, if higher reliability and lower current ripple are required. The proposed driver features high efficiency (90.8%), and a high power factor (PF) (0.995). In this paper, analytical results and design considerations at 100 kHz are presented, and a 100-W prototype with 110 \textV\text{AC} input was built to validate the theoretical analysis. [ABSTRACT FROM AUTHOR]

In this paper, a single-stage LED driver is proposed for a street lighting system. Two boost circuits that share a single inductor are formed by integrating the switches of a half-bridge $LLC$ resonant converter. Both boost circuits operate in the boundary conduction mode, which realizes a power-factor correction function. Because the input voltage of the LED driver is divided by two capacitors, the bus voltage is considerably reduced to almost the input peak voltage, rendering the novel single-stage LED driver to work suitably under high-input-voltage conditions. The soft-switching characteristics of the half-bridge $LLC$ resonant circuit are not affected by the integration of the switches; thus, the converter has a low cost and a high efficiency. A 100-W prototype was developed, and the efficiency was determined to be as high as 91.1% in a full-load state under a 220-V ac input. [ABSTRACT FROM PUBLISHER]