New DCM Operated Single Phase Bridgeless Cuk Derived Converters for Power Factor Correction

This paper presents a power factor corrected (PFC) new bridgeless (BL) Cuk Topologies for low power applications. A BL configuration of Cuk converter is proposed which eliminates the usage of diode bridge rectifier at the front end of the PFC converter, thus reducing the switching and conduction losses coupled with it. This new BL Cuk converter has two semiconductors switches. The current flow during each switching cycle interval of the converter reduces the conduction losses compared to the conventional Cuk PFC converter. It also reduces the input current ripple and Electromagnetic Interference (EMI). The inrush current during the starting period is limited and the input, output currents of the converter are continuous with minimum current ripple. Hence it is preferred mostly compared to other PFC circuits. The proposed topology works in the Discontinuous Conduction Mode (DCM) with simple control circuitry to achieve almost a unity power factor with less distortion in the input AC current. The switching of the power switches is done under zero current. The proposed PFC topologies are theoretically investigated and performance comparisons are made with the conventional rectifiers. The proposed PFC converter is simulated in MATLAB/SIMULINK with Fuzzy Logic Controller (FLC) and results are demonstrated to evaluate the effectiveness of the controller.

A RESEARCH TO HIGH-PERFORMANCE MULTI-LEVEL SINGLE-PHASE AC/DC POWER FACTOR CORRECT SWITCHING CONVERTER

This letter studies and analyzes the working features of main circuit of tri-level boost Power Factor Correct(PFC) converter and the advantages of tri-level switch converter in aspects of bearing high-voltage of power components,overall system loss and magnetic component selection based upon the single-level boost PFC switch converter.Besides,relying on the application of mi-croprocessor in power converter technology and DSP(Digital Signal Processing) chip's strong cal-culating capacity,the letter presents the adoption of modified scheme of tri-level boost PFC converter under the control of predictive control algorithm.Moreover,the operating principle and control method are specified,the results of circuit test and analysis are provided and the advantages of pre-dictive control technology-based multi-level boost PFC converter is verified.

An Investigation of Power Converters Fed BLDC Motor for Adjustable Speed

This paper reports the converter topologies which are employed for better Power Factor Correction at the input side. The Power Factor Correction is an important factor when considering the Power Quality. Based on the converter topologies, the Bridgeless converters are preferred in order to reduce the number of switching devices, losses associated with it and improve the Power Quality further more. This paper investigates about the Power Factor performances and conduction losses of the Bridgeless Power Factor Corrector Converters which see through the benefits and limitations by analyzing the Bridgeless Buck-Boost Converter, Bridgeless SEPIC converter and Bridgeless CUK converter. The resultant voltage is fed to the BLDC motor which is rapidly replacing the Induction motor for its better operating characteristics. These strategies are being analyzed using the MATLAB/Simulink software and the results are verified through the experimental analysis. The converter choice is preferred through the performance characteristics and Power Factor Correction at the supply. The Power Factor obtained should be within the acceptable limits under IEC 61000-3-2 standards.

A Flux DC Bias Suppression Scheme of Single-stage Full-bridge PFC Converters Based on Dead Zone Adjustment

由于单级桥式功率因数校正（power factor correction,PFC）AC/DC变换技术电路的特点,导致高频变压器存在偏磁现象,影响了系统正常工作。传统方式通过增加变压器气隙或使用隔直电容来防止变压器出现偏磁,但是该类方案影响了系统性能,并增加了电路的复杂程度。结合有源钳位单级PFC变换器工作特点,提出一种基于死区调节的偏磁抑制策略,通过改变系统的开关时序,能够有效抑制偏磁,具有不增加主电路复杂程度、不影响系统性能、数字控制和模拟控制都能够实现等优点。在提出抑制策略的基础上,设计实现电路,给出死区设计方法及影响规律,最后进行实验研究。理论分析及实验结果表明,该策略能够在不影响系统性能的基础上,有效抑制单级桥式PFC变换器的高频变压器偏磁。

An Improved Modulation Strategy for Single-phase Three-level Neutral-point-clamped Converter in Critical Conduction Mode

Two-level totem-pole power factor correction(PFC)converters in critical conduction mode(CRM)suffer from the wide regulation range of switching frequency.Besides,in highfrequency applications,the number of switching times increases,resulting in significant switching losses.To solve these issues,this paper proposes an improved modulation strategy for the single-phase three-level neutral-point-clamped(NPC)converter in CRM with PFC.By optimizing the discharging strategy and switching state sequence,the switching frequency and its variation range have been efficiently reduced.The detailed performance analysis is also presented regarding the switching frequency,the average switching times,and the effect of voltage gain.A 2 k W prototype is built to verify the effectiveness of the proposed modulation strategy and analysis results.Compared with the totem-pole PFC converter,the switching frequency regulation range of the three-level PFC converter is reduced by 36.48%and the average switching times is reduced by 45.10%.The experimental result also shows a 1.2%higher efficiency for the three-level PFC converter in the full load range.

一类三电平伪图腾柱无桥PFC变换器

针对传统二极管钳位型三电平整流器在单相电源前级功率校正(power factor correction,PFC)电路应用场景下全控开关器件数量多的问题,该文基于3种传统无桥PFC电路进行三电平电路拓扑设计,提出一类三电平伪图腾柱PFC电路(single-phase three-level pseudo totem-pole PFC circuit,STPT-PFC),该类三电平PFC具有双电感支路桥臂,两者相互配合工作为输入电流提供路径,在正负半周两电感支路桥臂工作于不同模态可有效降低分别流过两电感的电流;基于该类PFC的一个代表性电路,从工作电流路径过程、关键波形和调制脉冲分配等方面对其进行工作原理分析,并对其它电路进行电路特性总结,推导桥臂对地电压电平特性与开关脉冲分配的数学关系式。另外,该类STPT-PFC共有5种结构,结合该类STPT-PFC结构特点,提出统一区间判断条件的双层载波调制技术,该类STPT-PFC具有相同开关器件不同拓扑结构可采用同一调制方案的特点,便于该类调制技术移植。最后,基于STPT-PFC-I电路设计1台额定功率1 kW、直流输出电压400 V的实验样机,从稳态及动态两方面进行实验分析,实验结果验证所提出一类三电平伪图腾柱PFC电路的可行性和三电平统一双层调制方法的有效性。

三态Boost PFC变换器的高功率因数和轻载效率提升方法研究

工作于伪连续导电模式(pseudo-continuous conduction mode,PCCM)的三态Boost功率因数校正(power factor correction,PFC)变换器采用传统解耦控制,在输入电压增大时,存在功率因数较低的问题。文中结合三态Boost PFC变换器具有两个控制自由度的特点,从变换器的输入电流表达式出发,提出一种三态Boost PFC变换器的变占空比正弦参考电流控制方法,采用变占空比控制变换器的主开关管,正弦参考电流控制续流开关管,并对变换器参数和控制环路进行设计。相比于传统解耦控制的,变占空比正弦参考电流控制的三态Boost PFC变换器具有更高的功率因数,同时也具有快速动态响应与宽负载范围的优点。在此基础上,针对三态Boost PFC变换器轻载效率低的问题,提出混合模式控制方法提升其轻载效率。最后,通过一台400W的实验样机验证理论分析。

不同负载条件下DICM Cuk PFC变换器稳定性分析

重点分析了系统负载变化时,不连续电感电流模式Cuk功率因数校正PFC(power factor correction)变换器稳定性的变化情况。在变换器工作特性的基础上,根据谐波平衡法和Floquet理论分析,研究结果表明:当负载电阻变小时,即系统由轻载到重载变化时,系统发生了工频频率上的倍周期分岔。给出了系统发生倍周期分岔时的电阻,以及在输出电感、输入电压产生改变时和负载电阻共同构成的系统不稳定与稳定的边界区域图,基于输入电感电流-输出电压的相轨图和输出电压的谐波分析谱,更好地观察到系统的动力学行为。最后通过实验验证了理论分析的正确性。

一种带滤波结构的三电平PFC变换器拓扑结构研究

针对传统的功率因数校正(PFC)电源系统功率密度低、电压纹波大等缺点,该文提出了一种带滤波结构的三电平PFC变换器拓扑结构,用于抑制电压纹波并减小电源模块体积,提高功率因数校正电源系统的性能。通过理论计算和仿真分析,对整流器直流侧电压进行了对比,结果表明这一拓扑能够滤除90%的电压纹波,提高了整流器电压的精度与稳定性,仿真实验结果也验证了这一拓扑结构的可行性。

无电流传感复合前馈控制无桥功率因数校正变换器

有源功率因数校正(APFC)是AC-DC变换器的重要组成部分,其目的是改善输入侧电能质量,提高系统功率因数。传统的有源电流控制功率因数校正(PFC)变换器需要准确地提取升压电感电流,而双二极管式无桥PFC变换器升压电感位于整流部分之前,电感电流不再是单一方向流动,这使得其电流采样电路相比更复杂。为此该文提出一种基于观测器的无电流传感方案。方案中针对占空比误差的不确定影响修正了无桥PFC电流观测器算法,实现了占空比误差自适应的电流观测器,进一步基于所提观测器实现对负载信息的观测,设计出无电流传感的复合前馈控制方案,运用负载观测信息改进电流内环参考形式,同时利用输出电压纹波观测值进行2次谐波前馈补偿,最终实现无电流传感控制条件下变换器高动态响应设计。该文搭建了225 W单相双二极管式无桥PFC的实验样机,实验结果表明,在开关频率100 kHz时电流观测精度达到96.75%,所提控制方案输入电流的总谐波畸变率(THD)含量约为5%,功率因数(PF)约为99.85%,半载动态响应时间10 ms,相比于传统PI控制无桥PFC变换器提高了约90%。

基于二次型Buck PFC变换器的无频闪无变压器LED驱动电源

提出了一种基于二次型Buck功率因数校正(power factor correction,PFC)变换器的无频闪无变压器LED驱动电源,分析了其工作原理和工作特性。它由共用一个开关管的两个Buck变换器级联构成,其中前级Buck变换器实现PFC功能,后级Buck变换器调节LED电流。该电源无需使用高降压比的变压器也可以驱动低正向导通电压的LED,它只使用一个控制器不仅实现了PFC功能,而且极大的降低了流过LED的二倍工频电流纹波,从而实现无频闪。最后通过7W的实验样机验证了理论分析的正确性。

低输入电感电流纹波二次型Boost PFC变换器

针对Boost功率因数校正(power factor correction,PFC)变换器输入电感电流纹波大、电磁干扰(electromagnetic interference,EMI)问题严重的缺点,提出将二次型Boost变换器应用于PFC变换器,简称二次型Boost PFC变换器,并分析其电路工作模态。当输入电感工作于连续导电模式(continuous conduction mode,CCM)时,根据储能电感的工作模式(CCM和断续导电模式(discontinuous conduction mode,DCM)),将CCM二次型Boost PFC变换器分为CCM-CCM二次型Boost PFC变换器和CCM-DCM二次型Boost PFC变换器。分析不同交流输入电压等级下CCMBoost PFC变换器和二次型Boost PFC变换器的输入电感电流纹波和占空比变化范围。结果表明,与CCM Boost PFC变换器相比,CCM二次型Boost PFC变换器减小了输入电感电流纹波和占空比变化范围。最后,通过仿真和实验结果验证了理论分析的正确性。

变导通时间控制临界连续模式反激PFC变换器

提出了一种变导通时间(variable on-time,VOT)控制临界连续模式(critical conduction mode,CRM)反激功率因数校正(power factor correction,PFC)变换器的控制策略。引入输入电压和反激变压器辅助绕组电压参与CRM反激PFC变换器开关管的导通时间控制,解决了传统恒定导通时间(constant on-time,COT)控制CRM反激PFC变换器功率因数(power factor,PF)低和总谐波畸变(total harmonic distortion,THD)高的问题。分析传统COT控制CRM反激PFC变换器和VOT控制CRM反激PFC变换器的工作原理,实验验证结果表明,VOT控制CRM反激PFC变换器比传统COT控制CRM反激PFC变换器具有更高的PF值和更低的THD。

AC/DC Buck-Boost PFC变换器滑模变结构及PI调节器综合控制

以AC/DCBuck-BoostPFC变换器为主拓扑,提出滑模变结构电流内环控制与PI调节器电压外环控制相结合的综合控制系统,以实现变换器高性能的单位功率因数校正。仿真和实验研究结果表明,这种控制系统设计兼有滑模控制动态性能、鲁棒性好与PI调节器稳定性好的优点。

Boost PFC变换器直流母线电容等效串联电阻和容值的一种在线监测方法

电解电容是电源系统中易失效的元件,在线监测其等效串联电阻(equivalent series resistance,ESR)和电容值(capacitance,C)的变化十分关键。该文提出一种新的非侵入式在线监测升压(Boost)功率因数校正(power factor correction,PFC)变换器直流母线电容ESR和C的方法。通过分析直流母线电压,建立了ESR和C的实时在线计算模型。该方案无需额外的电流传感器,通过采样直流母线纹波电压和交流输入电压,结合电感电流信号,就可监测不同工作状态下的ESR和C,完成一台监测系统原理样机并进行实验,实验结果验证了所提方法的有效性。

平均电流控制的Boost PFC变换器最恶劣传导EMI频谱分析

平均电流控制的Boost PFC变换器可能工作于电感电流在半个工频周期内全连续、部分断续和全断续的模式,且不同工作模式下,变换器的传导EMI频谱存在差异。为了分析变换器的最恶劣传导EMI频谱并简化EMI滤波器的设计,首先给出变换器不同工作模式的输入电压和负载条件,并给出开关管漏源极电压的波形。通过分析开关管漏源极电压的各次谐波幅值特性指出,传导EMI开关频率基波的最恶劣情况出现在电感电流全连续的工作模式下,其它次谐波的最恶劣情况出现在负载较轻的条件下。

具有快动态响应和低输出电压纹波的二次型BoostPFC变换器

为了提高功率因数校正(Power Factor Correction,PFC)变换器对负载变化的动态响应性能,同时消除输出电压二倍工频纹波,本文将二次型Boost变换器应用于PFC变换器中,并分析了其工作原理。根据主电路电感的工作模式,可以将二次型Boost PFC变换器的工作区域划分为四个区域:CCM-CCM、CCM-DCM、DCM-CCM和DCM-DCM,本论文重点研究了二次型DCM-DCM Boost PFC变换器的输出电压纹波特性及其动态性能。研究结果表明,与传统DCM Boost PFC变换器相比,二次型DCM-DCM Boost PFC变换器可消除输出电压的二倍工频纹波,降低输入电感电流峰值,且提高了负载动态响应速度,极大地降低了输出电压超调量与跌落量。最后,通过实验结果验证了理论分析的正确性。

具有宽负载范围和低电压应力的三态反激PFC变换器

提出一种具有宽负载范围和低电压应力的三态反激功率因数校正(PFC)变换器拓扑。通过续流功率开关管和二极管,使该变换器工作于伪连续导电模式(PCCM),拓宽了传统不连续导电模式(DCM)反激PFC变换器的带载能力,并有效地降低了传统DCM反激PFC变换器中功率开关管所承受的电压应力。通过对电路工作模态及其稳态特性的分析可知,该变换器不仅具有较好的功率因数校正能力,还具有开关管电压应力低、负载范围宽等优点。最后,通过实验结果验证了该变换器的优越性。