面向高压大功率场合的三相三电平LLC谐振直流变换器研究

发布时间：2018-02-19 22:56

本文关键词： 三相三电平 LLC谐振直流变换器变频控制定频不对称控制软开关　出处：《南京航空航天大学》2014年硕士论文　论文类型：学位论文

【摘要】：在中大功率直流变换场合，对于传统的变换器如正激、半桥和全桥变换器，开关管的电压应力和电流有效值高，限制了变换器功率的进一步提高。为了降低开关器件的功率定额及应力，有学者提出三相三电平PWM直流变换器，有效降低了开关管的电压应力，减小了电流有效值。 LLC谐振变换器可在宽负载变化范围内实现开关管的零电压开关和整流二极管的零电流开关，其副边整流管电压应力仅为输出电压，适用于高压输出、中大功率应用场合，其常用控制策略是变频控制策略和定频变占空比的控制策略。为了结合上述两种变换器的优点，本文提出了具有简易结构的三相三电平LLC谐振直流变换器，该变换器的优点是开关器件数量少，电路结构简洁；开关管电压应力仅为输入电压一半，副边整流管电压应力仅为输出电压，适用于高压输入/输出场合；副边整流电流脉动频率高于传统单相直流变换器，可减小输出滤波电容；采用变频控制策略或者定频不对称控制策略，可在宽电压和宽负载范围内实现开关管的零电压开关和副边整流管的零电流开关，提高变换器的效率。本文详细讨论了变频控制和定频不对称控制策略下三相三电平LLC谐振直流变换器的工作原理。在变频控制策略下，应用基波分析法对变换器进行等效简化和建模，分析变换器在不同工作区间的增益特性，确定理想工作区域，并进行详细的参数设计。在定频不对称控制策略下，分析变换器的工作原理，并进行了仿真验证。最后，在实验室搭建了一台2kW的原理样机，，对理论分析结果进行实验验证。实验结果表明本文所提出的三相三电平LLC谐振直流变换器及其控制策略是可行的。
[Abstract]:In high power DC converter, to transform such as forward traditional, half bridge and full bridge converter, the voltage stress of the switches and the current effective value is high, limited to further improve the converter power. In order to reduce the quota and stress power switching devices, some scholars have put a three-phase three level PWM DC converter can reduce the voltage stress of the switches, reducing the current effective value.
LLC resonant converter can be in a wide load range and zero current switching tube zero voltage switch and rectifier diode switch, the secondary rectifier voltage stress is only applicable to the output voltage, high output voltage, high power applications, the common control strategy is frequency control strategy and constant frequency variable accounted for the control strategy is.
In order to combine the advantages of the two kinds of converter, is proposed in this paper has a simple structure of the three-phase three level LLC resonant DC-DC converter, advantages of this converter is a switching device number, the circuit structure is simple; the voltage stress of the switches is only half of the input voltage, the rectifier voltage stress is only the output voltage. Suitable for high voltage input / output applications; rectifier current ripple frequency is higher than the traditional single-phase DC converter can reduce the output filter capacitor; the frequency control strategy or the strategy of asymmetric control over a wide frequency, voltage and load range to achieve zero current switching zero voltage switching tube and secondary rectifier switch. To improve the efficiency of the converter.
This paper discusses in detail the frequency control and fixed frequency control strategy under asymmetric three-phase three level LLC resonant DC-DC converter working principle. In the frequency control strategy, the application of wavelet analysis method for equivalent simplification and modeling of the converter, analysis of converter in the gain characteristics of different working range, determine the ideal working area, and parameters detailed design. In the fixed frequency asymmetric control strategy, analysis of the working principle of the converter, which is validated by simulation.
Finally, a prototype of 2kW is built in the laboratory, and the theoretical analysis results are verified by experiments. The experimental results show that the three-phase three level LLC resonant DC converter and its control strategy proposed in this paper are feasible.

【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】：2014
【分类号】：TM46

【共引文献】