一种适用于高压输出的软开关多谐振直流变流器

将倍压整流技术和LLC多谐振变流器结合起来,构造出倍压整流LLC多谐振变流器.该变流器的变压器结构简单,副边只需要一个绕组;输出电容电压应力是输出电压的一半,无需额外的均压电路;只需要两个整流二极管,二极管的电压应力等于输出电压,电流应力等于输出电流,所以该变流器非常适合用于高压输出中小功率的DC/DC电源.另外,该变流器的所有功率半导体器件都工作于软开关状态,所以适用于高频高功率密度的场合.详细分析了该变流器的工作原理,软开关过程,输出电容的自动均压机理,并给出了关键的参数设计方法,采用该变流器技术的500V输出直流电源的实验结果验证了以上分析的正确性,满载效率达92.3%.     

A zero-current switching switched-capacitor DC-DC converter with reduction in cost,complexity, and size

This paper presents a new step-up switched-capacitor (SC) DC-DC converter which has many advantages such as reduction in investment cost, control complexity, number of components, voltage stress on components, and size over traditional topologies. In the proposed structure, power switches are reduced in number which in turn leads to the merits mentioned earlier and makes the converter more suitable for industrial applications. Furthermore, a previously introduced zero-current switching (ZCS) method is used here which provides soft switching for the devices. There is also a reduction in the number of required inductors to achieve ZCS due to the decreased number of switches in the proposed converter. The proposed converter is validated by comprehensive simulation results in MATLAB Simulink environment and also precise experimental results which show the acceptable performance of the proposed topology.     

Bidirectional isolated three-phase dc-dc converter using coupled inductor for dc microgrid applications

The main objective of this project is to study the analysis and design of an isolated three-phase bidirectional dc-dc converter connected to the dc microgrid system. The proposed topology achieves efficient power conversion with a wide input voltage range, continuous input current, and bidirectional operation. In forward mode operation, the topology acts as a three-phase push-pull converter to reach a step-up voltage conversion ratio (90 to 450 V ). In backward mode operation, the converter acts as an interleaved flyback converter to provide a step-down voltage conversion ratio (450 to 90 V ). Over and above that, in both operation senses, the dc voltage gain is presented. The main advantages of this topology are high-switching frequency, the three-phase transformer that provides galvanic isolation between the dc voltage link bus to the battery or ultra-capacitor storage, and input/output filters size reduction. Besides, a fewer number of power switches, the frequency of output voltage, and input current ripple are three times higher than the switching frequency. The three active switches are connected to the same reference, which simplifies the gate drive circuit. Ultimately, the theoretical analysis of the proposed topology is carefully confirmed with the experimental results of the 4 kW converter prototype.     

ZCS谐振开关电容变换器的拓扑结构改进

零电流(ZCS)谐振开关电容变换器是开关电容变换器的一种新拓扑形式.通过建立ZCS谐振开关电容变换器的开关布尔矩阵,提出了一种分析其有效开关模态,辨识潜电路路径的新方法.当潜在回路出现时,变换器的输出特性出现非预期的变化.同时,通过对潜在回路电流路径的分析,提出了一种ZCS谐振开关电容变换器的改进电路,从而从根本上消除了变换器中的潜电路现象.实验结果证明了理论分析的正确性和有效性.     

一种带开关电容的二次型高增益Boost变换器的研究

光伏、燃料电池等发电系统的输出电压等级较低且输出电压不稳定,需要通过高增益Boost变换器把较低等级的直流电压进行升压以满足并网要求。提出一种带开关电容的二次型高增益Boost变换器,在传统二次型Boost变换器的基础上引入开关电容单元,提高了变换器的升压能力,实现了以较小的占空比获得较大的电压增益,拓宽了输入电压范围。同时,该变换器改进了传统二次型Boost变换器开关管和二极管电压应力过大的缺点,减小了开关管的导通损耗和二极管的反向恢复损耗。另外,该变换器还有输入电流连续、输出电压纹波小的优点。分析了该变换器的工作原理及工作特性,在理论研究的基础上搭建了一台12 V/60 V的实验样机,实验结果证明了理论分析的正确性。     

一种单输入双输出高增益DC-DC变换器

随着分布式发电在中低压场合的应用越来越广泛,对高增益直流变换器的需求日益增加。提出一种新型单输入双输出高增益DC-DC变换器。该变换器在传统Boost电路基础上引入电容和二极管组成极性反向极,功率端口通过差分连接方式互联,提高了变换器电压增益,降低了开关管电压应力;同时端口功率控制彼此独立,进一步提高了电能路由的灵活性。详细分析了该变换器的电路结构和工作原理,推导出稳态特性下的电压增益、主要开关器件电气应力以及电流纹波等表达式。在此基础上,提出了基于矢量时间作用的模型预测控制策略,建立了该变换器预测模型、推导出开关管矢量时间以及设计了目标函数寻优过程。最后,通过仿真和实验验证了所提变换器及其控制策略不仅可行、有效,而且具有高运行效率与低电压应力。     

Interleaved step-up converter with a single-capacitor snubber for PV energy conversion applications

In this paper, an interleaved step-up converter with a single-capacitor snubber for PV energy conversion applications is proposed. The step-up converter adopts two sets of boost converters with an interleaved fashion and coupled-inductor technology to reduce output ripple current and increase output power level. To achieve higher conversion efficiency and reduce switching losses of the proposed converter, a lossless single-capacitor turn-off snubber is introduced. Therefore, the conversion efficiency can be increased significantly. In order to draw the maximum power from the PV arrays, a perturbation-and-observation method and a microcontroller are associated to implement maximum power point tracking (MPPT) algorithm and power regulating scheme. Finally, a prototype of a soft-switching interleaved soft-switching boost converter with coupled inductors has been built and implemented. Experimental results have obtained to verify the performance and feasibility of the proposed converter for PV arrays applications.     

Non-isolated high step-up dual-input DC-DC converter with zero-voltage transition

In this paper, a non-isolated dual-input DC-DC converter with zero-voltage transition (ZVT) is proposed for renewable energy systems. The proposed converter has high step-up conversion gain without using any transformer or coupled inductors. The proposed structure consists of two boost cells, one diode-capacitor multiplier cell, and one ZVT auxiliary circuit. The main switches turn on and off under zero voltage condition and the auxiliary switch turns on under zero current condition and turns off under zero current and zero voltage conditions. Soft switching conditions, high efficiency, continuous current of input sources, low-voltage stress on switches, and returning the energy of the auxiliary circuit to the boost cell connected to the lower-voltage input are the main advantages of the proposed converter. The steady-state analysis of the converter and operation intervals are discussed. A 160-W prototype of the proposed converter is designed and implemented. Experimental results confirm the theoretical analysis. The efficiency reaches 96.7% at the nominal load by providing soft-switching for all switches. The proposed topology can be extended for multi-input applications by expanding the number of diode-capacitor multiplier and input boost cells.     

Boost型无频闪谐振降压式LED驱动电源分析与设计

传统的二次型Boost功率因数校正变换器只能实现升压输出,在一定程度上限制了其在LED驱动电源中的应用。本文基于二次型Boost变换器提出了一种Boost型无频闪谐振降压式LED驱动电源,并分析了其工作原理及特性。该LED驱动电源利用一个有源开关管将二次型Boost变换器与一个谐振网络进行整合。与传统的二次型Boost变换器相类似,该LED驱动电源可以实现高效率和高功率因数。此外,该LED驱动电源可实现低电流纹波和降压变换输出。最后,搭建了一台84W的实验样机,最高效率可达到92.88%,验证了理论分析的正确性及可行性。     

具有软开关特性的串联电容型高频高增益双向DC-DC变换器

本文提出了一种具有软开关特性的串联电容型高频高增益双向DC-DC变换器。在传统的基于耦合电感的升降压电路的基础上,引入了一个电容和一个开关管,有效提升了变换器增益。同时构造了基于串联电容谐振回路,为开关器件的软开关创造条件。并且为了减少振荡和无源器件的体积,可将耦合电感的漏感作为谐振电感,从而减少了无源元件数目,在高频工作条件下可实现高功率密度和高效率。本文详细介绍了该变换器的工作原理和参数设计方法,并搭建了一台48V/5V、50W、750kHz的实验样机,相关结果证明所提拓扑及设计方法的正确性。     

一种双输入高增益DC-DC变换器

针对光伏发电系统输出电压低、供电稳定性差等问题,提出一种非隔离双输入高增益直流升压变换器,该变换器在2个BOOST变换器的基础上引入了开关电容电路,实现了高电压增益,且两输入源可以单独或同时向负载供电。分析该变换器的电路结构和工作原理,推导出了3种供电模式下变换器的电压增益表达式以及主要开关器件电压应力,给出了两路同时供电时输入电流之间的关系。最后,搭建了一台100W的实验样机,实验验证了该变换器具有电压增益高、开关器件电压应力低、控制简单、可以灵活供电等优点。     

改进型零电压转换PWM软开关功率变换器的实现机理分析

为改进传统谐振缓冲功率变换器(RSI)应用于高精度场合纹波较大的问题,提出一种改进型零电压转换(ZVT)脉宽调制(PWM)软开关功率变换器。通过LC环节减小输出电流纹波,并采用负载分段实现软开关的方式。轻载下利用交变的滤波电感电流实现主开关器件的零电压开通,重载下通过合理的导通谐振回路实现软开关,同时辅助开关器件实现零电流开关。该拓扑可采用PWM控制,具有效率高、纹波噪声小和开关频率固定的优点。通过分析电路的实现机理,对各工作时区进行解析计算,并给出实现软开关的条件。最后通过实验,在200kHz的开关频率下,验证了电路的有效性。相比于硬开关,效率得到了很大的提升,而相比于RSI在效率上虽有降低,但输出噪声却大幅减小。     

Series resonant high‐voltage DC–DC converter with reduced component count

This paper proposes a novel zero‐current‐switching series resonant high‐voltage DC–DC converter with reduced component count. The series resonant inverter in the proposed topology has two power switches (insulated‐gate bipolar transistors, IGBTs), two resonant capacitors, and only one high‐voltage transformer (HVT) with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. The leakage inductances of the transformer's primary windings together with the resonant capacitors form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with interleaved half switching cycle. The secondary winding of the HVT is connected to a bridge rectifier circuit to rectify the secondary voltage. The converter operates in the discontinuous conduction mode (DCM) and its output voltage is regulated by pulse frequency modulation. Therefore, all the power switches turn on and off at the zero‐current switching condition. The main features of the proposed converter are its lower core loss, lower cost, and smaller size compared to previously proposed double series resonant high voltage DC–DC converters. The experimental results of a 130‐W prototype of the proposed converter are presented. The results confirm the excellent operation and performance of the converter. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

一种具有自动均压均流特性的组合式LLC谐振变换器

提出一种具有自动均压和均流特性的组合式LLC谐振变换器。该变换器拓扑基于多个LLC模块的ISOP结构,通过在变换器前级开关电容网络中加入飞跨电容实现各串联模块输入端电压的均衡,在不同模块的谐振槽中串联耦合电感实现各模块电流的均衡。该拓扑保持了传统LLC谐振变换器的高效率、软开关和低电磁干扰(EMI)等优良特性,且具有控制简单、系统可靠性高等优点,非常适用于高降压比、大功率输出场合。以两个LLC模块的组合式变换器为例,对该拓扑的均压和均流原理进行详细分析。最后,通过一台输入400~550V、输出48V/24A的实验室样机,对该拓扑的均压和均流效果进行实验验证。     

最小原边通态损耗高压输入多谐振推挽变流器

为了提高新型燃料电池能源系统能量转化传递的效率,延长燃料电池本体寿命,提出了一种最小化原边通态损耗的高压输入软开关多谐振推挽变流器。该变流器继承了传统推挽变流器和传统LLC多谐振变流器的全部优点,可用于低成本、高效高功率密度场合,且其原边所有主开关管上的电压应力均为输入电压,故较传统推挽变流器更适用于高压输入的场合。此外该拓扑还通过将原边电流均分至2个推挽支路的方式将原边通态损耗降为传统推挽变流器的一半,提高了转换效率,因而该新颖变流器非常适合作为燃料电池系统中后级单向宽范围输入的高效率直流电源。在详细分析了该变流器的工作原理和关键参数的设计方法后,以一台1 kW的实验样机验证了该拓扑的可靠性和有效性。样机的满载效率达到了97%。     

Step-up Transformerless Seven-level DC-AC Hybrid Topology for Interconnection of Renewable-based DC Sources to Microgrids

This article introduces a new step-up transformerless multi-level DC-AC hybrid topology for interconnecting renewable DC sources to loads or microgrids. This enabling technology incorporates the best characteristics of three modified basic topologies—a DC-DC multi-level boost converter, a DC-DC multi-level buck converter, and an H-bridge—to obtain a seven-level step-up DC-AC hybrid structure using only one DC input and nine power switches for a single-phase output with field-programmable gate array based control. The advantages of the step-up seven-level structure compared to other proposals are higher efficiency, a reduced number of power switches, and high power density associated with transformerless characteristic. Furthermore, in contrast to conventional topologies, the proposed design does not require voltage/current monitoring of the capacitors or a capacitor-balancing control scheme, and only one DC source input is used. Consequently, a high-performance configuration is obtained. The laboratory results demonstrate the validity of the design and the performance of the prototype.     

基于有源开关电感网络和DCM单元组的DC-DC升压变换器

针对传统Boost变换器存在升压能力有限、开关器件电压应力大和效率低等问题,基于有源开关电感网络和二极管-电容单元组(diode-capacitor multipliers,DCM)提出了一种新型高增益升压变换器拓扑,该拓扑在实现高增益的同时避免了极大的占空比,并且有效地降低了开关器件的电压应力。详细分析了所提变换器在连续导电模式,断续导电模式和边界导电模式下的工作原理和工作性能,推导了变换器的电压增益、开关管的电压和电流应力大小,并推演出n个DCM单元级联的高增益升压变换器拓扑。与其他文献提出的变换器在电压增益、元器件数量、开关管电压应力等方面进行详细的对比,最后搭建了一台功率约为130 W的实验样机,实验结果验证了理论分析的正确性。     

级联H桥五电平变流器工况分析与验证

以单相两功率单元级联为例,阐述了级联H桥五电平变流器的拓扑结构和载波相移SPWM(CPS-SPWM)调制策略.从该变流器的运行工况着手,给出了这种变流器在CPS-SPWM调制方法下的工作原理,并从数学角度推导了变流器开关切换、输出电压、电流流向以及均衡电压等情况,理论推导表明CPS-SPWM调制方法应用在级联多电平逆变器上的可行性、可靠性和控制的简易性,为实现调制方法的优化和拓扑结构的改进提供了理论基础.同时对五电平变流器的运行工况进行了详尽的分析,推导出了五电平变流器的数学模型,并进行了仿真和实验验证.基于DSP与FPGA,研制了多路PWM脉冲发生器,既简化了电路的设计,提高了系统的可靠性,又可保证整个系统功率元件驱动信号的同步.实验结果表明,这种变流器能在较低的器件开关频率下实现较高等效开关频率的效果,运行工况稳定,在高压、大功率场合有一定的工程应用前景.     

一种高效倍压升压型软开关功率因数校正电路

提出一种高效零电压转换倍压升压型变换器的功率因数校正电路。新型软开关技术可以实现整流器主开关和无源开关零电压转换,而辅助开关零电流通断。所述软开关技术没有增加电路主开关的电压和电流应力。由于所用电路主电路导通流经更少的半导体功率器件,因此具有较少的器件导通损耗。该电路结构适合低压输入和中高功率应用场合。计算机仿真和实验样机验证了理论预期。该样机实现转换效率高达97%,功率因数为0.992。     

一种新型的高升压Boost变换器研究

由于清洁能源的广泛应用,电力电子变换器成为了研究的热点.将高升压比的Boost变换器用于清洁能源发电系统中,需要考虑变换器的升压能力和效率.针对传统变换器的缺点,提出了一种新型的高升压Boost变换器,根据其拓扑结构建立了等效的平均数学模型,推导出了该变换器升压比的计算公式.最后在MATLAB下搭建了仿真电路对所提出的变换器进行验证.理论分析和仿真结果表明了所提出的Boost变换器相比于传统Boost变换器具有高升压、开关器件电压应力低和转换效率高的优点.