【作者】 杨孟雄；

【导师】 阮新波；

【作者基本信息】 南京航空航天大学 ， 电力电子与电力传动， 2008， 硕士

【摘要】 燃料电池能量转换效率高,污染小,适用性强,被誉为继水力、火力、核能之后第四代发电装置。在燃料电池供电系统中,一般加入储能元件和双向变换器来辅助供电,以提高整个系统的动态性能。双向变换器的动态响应将直接影响到燃料电池供电系统的动态性能。本文从电路拓扑和控制方式两方面来讨论双向变换器的设计,并提出在两端“源”的场合下双向变换器的软起动方法。在电路拓扑方面,论文将三电平结构引入到两电平Buck-Boost双向变换器中,得到三电平Buck-Boost双向变换器(以下简称三电平双向变换器),其优点是电感可以大大减小,有利于提高变换器的动态响应。论文分析三电平双向变换器的工作原理、电路特性和参数设计,并研制一台1kW的原理样机进行实验验证。在控制电路方面,论文介绍PWM控制的边带效应,引入多频域模型分析两电平双向变换器和三电平双向变换器的控制环路带宽。由于边带效应的存在,两电平双向变换器的带宽最高只能到开关频率的二分之一,而三电平双向变换器中PWM交错控制可以消除边带频率fs-fp的边带效应,该变换器的带宽最高可以达到开关频率,是两电平双向变换器的两倍,因此三电平双向变换器具有更好的动态响应。论文通过仿真分析和对比,验证三电平双向变换器的动态特性好于两电平双向变换器。在燃料电池供电系统中,双向变换器工作在两端“源”的场合下,传统软起动方法将会导致反向电流出现,并因此损坏变换器。论文提出一种新颖的两段式软起动方法,它分两个阶段分别让主控管和被控管的占空比从零开始逐渐增加,有效防止反向电流的出现。将该方法分别应用到两电平和三电平双向变换器中,并进行实验验证,实验结果表明该方法是有效的。更多还原

【Abstract】 Fuel cell has the advantages such as high efficiency, low pollution and good adaptability, and it is a kind of potential generation device. In fuel cell power system, energy storage device and bi-directional dc-dc converter (BDC) are employed to improve the system dynamic performance. Therefore, fast dynamic response is an important issue in BDC. This thesis disusses the design of BDC in the aspects of topology and control, and the soft-start of BDC when the input and output sides are respectively connected to an independent voltage source is also discussed.In the aspect of topology, the three-level (3L) switch cell is introduced to buck-boost BDC and thus a 3L buck-boost BDC is obtained. The inductor of 3L buck-boost BDC is significantly reduced, so the dynamic response is improved. The operation principles, characteristics and parameter design are discussed in this thesis, and the theoretical analysis is verified by a 1kW prototype.In the aspect of control, the sideband effect of pulsewidth modulation (PWM) is presented, and the multi-frequency model is introduced to analyze the bandwidth of two-level (2L) and 3L BDCs. It is deduced that the sideband effect in 3L BDC is eliminated by adopting the interleaved control, and hence the bandwidth of 3L BDC can be moved up to as high as the switching frequency, twice of that of 2L BDC. Consequently, 3L BDC is expected to have better dynamic performance. Simulation results are provided to compare the dynamic performance of 2L and 3L BDCs, and it is shown that the later is better.In fuel cell power system, the input and output sides of the BDC are respectively connected to an independent voltage source. Using the traditional soft-start method will lead to huge inverse current and it will damage power devices. This thesis proposes a two-phase soft-start method, which lets the duty cycles of the active switch and passive switch increase slowly from zero in two successional phases of time, and thus prevents the inverse current effectively. The proposed soft-start method is applied to the 2L and 3L BDCs and the effectiveness of the method is verified by the experimental results.更多还原