【作者】 郝世强；

【导师】 全书海；

【作者基本信息】 武汉理工大学 ， 控制科学与工程， 2012， 硕士

【摘要】 双向DC/DC变换器作为微电网系统电力储能环节的重要组成部分,对微电网稳定运行非常重要,而其损耗和效率直接关系到变换器能否健康运行,同时与经济效益密切相关,因此研究微电网用双向DC/DC变换器的损耗和效率问题具有很高的实用价值。本文以一台双向DC/DC样机主电路为效率优化对象,针对功率器件、磁性元件和滤波电容三类器件在实际电路中所存在的损耗问题,开展了双向DC/DC变换器的损耗及效率优化的研究。本文主要研究内容如下：设计出了满足样机指标的双向DC/DC变换器拓扑结构,并采用常规计算方法,从实现DC/DC基本功能出发,计算出了主电路各部分参数,包括高频变压器、反激绕组、滤波电容和功率器件。所设计的电路拓扑和参数将作为损耗和效率优化研究的对象和入口参数。分析了快恢二极管和IGBT的开关过程,得出了其损耗的近似表达式和影响因素,并对硬开关双向DC/DC进行了功率器件损耗实验。采用有损缓冲和软开关这两种损耗优化方案,并做实验对比,重点讨论了充电ZVZCS和放电ZVS软开关实现条件和主要电路模态,提出了软开关辅助参数迭代优化策略,得出了优化结果,并通过实验证明了该参数迭代优化方法的正确性。讨论了磁芯损耗和绕组损耗的产生原因和影响因素,分析了双向DC/DC变换器中变压器和反激绕组的工作波形与损耗计算方法,并对双向DC/DC进行了磁性元件损耗实验。提出了变压器和反激绕组的损耗优化方案,并进行了实验对比,从发热、效率、成本和体积等方面综合考虑,选择出了最优的解决方案,使变换器性能显著提升。分析了电容等效损耗模型,得出了双向DC/DC两个滤波电容的不同的损耗表达式,并进行了滤波电容损耗实验。提出了三种滤波电容的损耗优化方案,并从损耗、整机效率、纹波电压、成本和体积等多方面进行了实验对比,确定了综合性能最优的方案,同时实现了电容低温升、高效率、低纹波、低成本和小体积。综上所述,本文以微电网用双向DC/DC变换器为优化对象,提出了功率器件、磁性元件和电容损耗的优化方法,采用实验对比的方法证明了优化方法的有效性,为电路进一步降低热耗、提高效率和提升功率密度提供了思路和依据。更多还原

【Abstract】 As the key component of microgrid’s electric power storage system, the bi-directional DC/DC converter is of great significance to the grid’s stability. The converter’s power losses and efficiency are closely related to the whole system’s well-running and economic benefits. Therefore, the study on losses and efficiency of bi-directional DC/DC converters in the microgird system is of much practical use. This dissertation mainly studies the optimization of a bi-directional DC/DC prototype’s losses and efficiency centering on three different kinds of practical loss problems: power device losses, magnetic element losses and filter capacitor losses. The main contents of this dissertation are as follows:The topology of the bi-directional DC/DC converter is designed for the microgrid system. The parameters of the transformer, flyback winding, filter capacitors and power devices are calculated to meet the performance indexes, using common calculation methods from the standpoint of function implementation. These circuit parameters are the object and suction variables of subsequent efficiency optimization.Switching processes of fast recovery diode (FRD) and IGBT are analyzed to deduce the approximate expression and main factors of losses. Loss experiments of the bi-directional hard-switching DC/DC converter are made to analyze power device losses. The dissertation adopts two loss optimization schemes:the lossy snubber circuit and soft-switching, and compares the two scheme’s experimental results in detail. Based on soft-switching conditons and equivalent circuits of ZVZCS in charging mode and ZVS in discharging mode, a iteration optimization strategy of the soft-switching auxiliary circuit is presented to determine the optimization results. The experimental results indicate the effectiveness of optimization strategy.The main reasons of magnetic core loss and winding loss are analyzed to deduce the magnetic loss expression on the base of the woking waveforms of the transformer and flyback winding. Magnetic loss experiments are made. The optimization method is studied for the loss of the transformer and flyback winding. By considering all factors, including heat, efficiency, cost and volume, etc, the dissertation selects the best scheme, significantly enhancing the converter’s performances.The capacitor equivalent loss model is analyzed to deduce the approximate expression of two filter capacitors in the bi-directional DC/DC conveter. Filter capacitor loss experiments of bi-directional DC/DC converter are made. Three optimization methods are presented for the loss of filter capacitors. Considering such aspects as loss, efficiency, ripple voltage, cost, and volume, this dissertation presents the best capacitor optimization scheme and its experimental results, realizing capacitor’s low loss, high efficiency, low ripple voltage, low cost and small volume.In summary, studies on optimization methods have been made for the losses of power devices, magnetic elements and filter capacitors in the bi-directional DC/DC conveter. The experimental comparions are made to prove the effectiveness of these optimization methods. The studies on loss and efficiency optimiztion can serve as ideas and foundations,in order to further reduce thermal loss, enhance efficiency and increase the power density.更多还原