断续模式无桥Boost PFC变换器的研究

发布时间：2018-08-20 14:26

【摘要】：实现电源的“绿色化”,减小谐波污染和电磁干扰,已成为电源研发设计的一个基本要求。在电源系统中引入功率因数校正技术可以有效地提高输入功率因数,降低谐波电流对电网的污染,以保证电网的供电质量,避免谐波干扰。在目前功率因数校正技术的研究中,其核心问题即为如何实现高效率、高功率因数和高功率密度。常规采用单相PFC技术的各类电气设备中,通常采用整流桥先将交流电转化为脉动的直流电,再经过PFC变换器实现功率因数校正功能。随着变换器功率等级的不断提高,整流桥的损耗在变换器整体损耗中所占的比例越来越大,严重影响了变换器效率的提升。因此,无输入端整流桥的无桥PFC变换器因为高效率成为了人们关注的焦点。本文首先分析了电感电流断续模式下基本型无桥Boost PFC变换器的工作原理,并对其电路特性进行了详细的数学推导。通过理论分析发现,定频定占空比控制下的断续无桥Boost PFC变换器虽然具有控制简单、功率器件开关损耗较小等优点,但在输入输出电压比值较大时功率因数较低。基于以上理论分析,本文设计了一台500W的样机并进行了实验验证,实验结果证明了无桥PFC拓扑高效率的优点,样机最高效率达98.5%,随着输入电压的增加,网侧电流波形畸变,功率因数下降明显。为了改善断续模式下变换器功率因数较低的缺点,本文通过对理想占空比的拟合计算,提出了一种较为简单的变占空比控制策略。与定占空比控制相比,本文所采用的方法可以有效提高输入功率因数,减小输入电流纹波,同时保证变换器高效率的优点。在此基础上,本文完成了一台变占空比控制500W样机的实验验证,实验结果验证了该控制方法的有效性。断续模式下的PFC变换器电压电流应力大,一般仅适用于中小功率场合。为了适应更大的功率需求,扩大断续模式无桥PFC变换器的应用场合,本文将交错并联技术引入无桥Boost PFC变换器,分析了电感电流断续模式下两路交错并联无桥Boost PFC变换器的工作原理和电路特性,并在理论分析的基础上完成了一台1kW的样机实验。由于变换器中功率器件存在寄生参数、电感存在非线性等非理想因素,影响变换器的工作特性。论文通过详细的数学分析和讨论,研究了电路中典型非线性因素对变换器特性的影响。本文首先考虑功率器件的寄生参数,讨论了变换器的工作特性,分析了其参数大小与电流畸变的数学关系,并通过仿真验证了理论分析的正确性。其次,本文采用回转器-电容模型对变换器中的非线性电感进行了数学建模,给出了详细的模型参数计算方法,并进行了仿真验证。
[Abstract]:The realization of "green" power supply and the reduction of harmonic pollution and electromagnetic interference have become a basic requirement of power development and design. The introduction of power factor correction technology in power supply system can effectively improve the input power factor and reduce the pollution of harmonic current to the power network so as to ensure the power supply quality and avoid harmonic interference. In the current research of power factor correction, the key problem is how to achieve high efficiency, high power factor and high power density. In the conventional single-phase PFC technology, rectifier bridge is usually used to convert AC to pulsating DC first, and then to realize power factor correction through PFC converter. With the continuous improvement of the power level of the converter, the loss of the rectifier bridge accounts for more and more of the overall loss of the converter, which seriously affects the efficiency of the converter. Therefore, no input rectifier bridge without bridge PFC converter because of high efficiency has become the focus of attention. In this paper, the working principle of the basic bridge free Boost PFC converter in the intermittent mode of inductance current is analyzed, and the circuit characteristics of the converter are derived in detail. Through theoretical analysis, it is found that the intermittent non-bridge Boost PFC converter with fixed frequency and duty cycle control has the advantages of simple control and low switching loss of power devices, but the power factor is lower when the ratio of input and output voltage is high. Based on the above theoretical analysis, a 500W prototype is designed and verified by experiments. The experimental results show that the bridge free PFC topology has the advantages of high efficiency. The maximum efficiency of the prototype is 98.5. With the increase of input voltage, the grid-side current waveform is distorted. The power factor decreased obviously. In order to improve the low power factor of the converter in intermittent mode, a simple variable duty cycle control strategy is proposed by fitting the ideal duty cycle. Compared with the constant duty ratio control, the proposed method can effectively improve the input power factor, reduce the ripple of input current and ensure the high efficiency of the converter. On this basis, an experimental verification of a 500W prototype with variable duty cycle control is carried out, and the effectiveness of the control method is verified by the experimental results. The voltage and current stress of PFC converter in intermittent mode is large, and it is only suitable for medium and low power situations. In order to meet the greater power demand and expand the application of intermittent mode non-bridge PFC converters, this paper introduces the staggered parallel technology into bridge-less Boost PFC converters. The working principle and circuit characteristics of two staggered parallel bridge free Boost PFC converters in intermittent inductance current mode are analyzed. Based on the theoretical analysis, a prototype experiment of 1kW is completed. Because of the parasitic parameters of power devices and the nonideal factors such as the nonlinearity of inductors, the operating characteristics of the converters are affected. Through detailed mathematical analysis and discussion, the influence of typical nonlinear factors on converter characteristics is studied in this paper. In this paper, the parasitic parameters of power devices are considered, and the working characteristics of the converter are discussed. The mathematical relationship between the parameters and the current distortion is analyzed, and the correctness of the theoretical analysis is verified by simulation. Secondly, the nonlinear inductance in the converter is modeled by the gyralizer-capacitance model, and the detailed calculation method of the model parameters is given and verified by simulation.
【学位授予单位】：南京航空航天大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TM46

【参考文献】