楼宇直流配电系统关键技术研究综述

随着新能源和电力电子装置的大量应用,楼宇直流配电系统相比于传统交流系统具有技术与经济上的优势。首先对国内外楼宇直流配电领域的相关新技术和发展现状进行了梳理。然后从技术角度对楼宇直流配电系统的拓扑结构、负载与电源、电压等级与经济性、优化管理系统以及对应的保护技术等方面进行了分析归纳总结。最后从楼宇直流配电系统的发展方向以及与能源互联网的配合进行了展望。     

应用于车载充电器的双向DC-DC变换器综述

在车载充电器的工作环境中,双向DC-DC变换器要满足功率密度大和宽输出电压范围以及体积小和效率高等条件。根据是否存在电气隔离,车载充电器的双向DC-DC变换器拓扑大致可分为非隔离型和隔离型。不同类型的变换器其拓扑结构和控制方法都不尽相同,相应地有不同的性能表现,同时,宽禁带器件的发展也在提升双向DC-DC变换器性能方面表现出了巨大的潜力。对这些拓扑和控制方法的演变过程进行了详细地分类和总结,对新器件带来的影响进行了综合叙述,同时归纳了目前仍存在的问题,最后提出对其的展望与总结。     

基于组合型双向DC-DC变换器的超级电容储能系统控制策略分析与设计

研究了一种基于组合型双向DC-DC变换器BDC(bidirectional DC-DC converter)的超级电容储能系统,该系统采用多组多通道交错Buck/Boost双向变换器串联,既可实现开关电流和电压应力的降低也可实现电感量的减小,同时有助于减轻超级电容单体电压低与应用场合电压高间的矛盾。串联变换器模块间的均压控制是该系统稳定运行的关键之一。基于双向变换器的小信号模型分析了超级电容储能系统电流控制与变换器模块均压控制的关系,设计了组合型双向DC-DC变换器的双闭环控制策略,在稳定控制超级电容充/放电电流的同时实现模块输入电压均衡的解耦控制。进一步根据母线电压变化及超级电容荷电水平提出了储能系统能量控制策略。通过两组三相交错Buck/Boost级联BDC储能系统的实验验证了控制策略的有效性。     

超级电容器储能控制技术研究

提出了双向DC-DC变换器在超级电容器充放电过程中的控制方法,能够解决绝大多数需要对超级电容器充放电的场合。在PSCAD/EMTDC电力系统仿真软件中构建超级电容器的充放电电路模型,通过对无补偿时双向控制模型分析,采用PI或者PID补偿环节实现系统的稳定,并进行仿真验证。为减小充电电流脉动,进一步提出对超级电容器进行多重充电的思路,给出仿真结果。仿真系统的稳定和良好的仿真结果说明所提出的方法可行。     

BDC钻头的现场应用技术

本文结合现场实际分析了BDC钻头的适用性、技术性、钻井参数和磨损情况,阐述了钻进及防斜纠斜中正确使用BDC钻头的操作程序及注意事项。     

BDC工艺对废水脱氮除磷的研究与应用

研究BDC工艺除氮脱磷,讨论pH值、曝气、悬浮物等因素的影响,并对BDC工艺中脱氮除磷的相互影响进行了探讨,给出了同时脱氮除磷的BDC运行方法,使磷铵厂氮磷废水达到中水回用的目的。     

基于超级电容的双向DC-DC变换器控制研究

针对轨道交通1 500 V系统再生制动能量利用,研究了基于超级电容储能的输入串联多相并联双向DCDC变换器的控制及其系统能量管理策略。采用输入串联、多支路并联的拓扑结构降低了功率器件电压应力和电流应力及减小了无源滤波器件的体积,同时降低了1 500 V系统对储能元件超级电容的耐压及模组均压控制的要求,使得系统的可靠性更高。针对该拓扑结构的特点,结合工程实际应用,考虑超级电容容值参数差异性及大内阻的特点,以超级电容的能量利用最大化为优化目标,对其充放电过程中超级电容电荷状态误判及系统输入输出侧均压控制策略进行了优化设计。最后通过仿真和实验验证了所提控制策略的有效性。     

Optimization of a heavy-duty compression-ignition engine fueled with diesel and gasoline-like fuels

Optimal injection strategies for a heavy-duty compression-ignition engine fueled with diesel and gasoline-like fuels (#91 gasoline and E10) and operated under mid- and high-load conditions are investigated. A state-of-the-art engine CFD tool with detailed fuel chemistry was used to evaluate the engine performance and pollutant emissions. The CFD tools feature a recently developed efficient chemistry solver that allowed the optimization tasks to be completed in practical computer times. A Non-dominated Sorting Genetic Algorithm II (NSGA II) was coupled with the CFD tool to seek optimal combinations of injection system variables to achieve clean and efficient combustion. The optimization study identified several key parameters that influence engine performance. It was found that the fuel volatility and reactivity both play important roles at the mid-load condition, while the high-load condition is less sensitive to the fuel reactivity. However, high volatility fuels, such as gasoline and E10, were found to be beneficial to fuel economy at high-load. The study indicates that with an optimized injection system gasoline-like fuels are promising for heavy-duty CI engines due to their lower NOx and soot emissions and higher fuel economy compared to conventional diesel fuels. However, the high in-cylinder gas pressure rise rate associated with Partially Premixed Combustion of gasoline-like fuels can become problematic at high-load and the low-load operating limit is also a challenge. Potential solutions are discussed based on the present optimization results.     

Computational thermodynamic analysis of compression ignition engine

This paper presents diesel engine simulation taking into consideration heat transfer and variable specific heats. A dual Weibe function is used to model the heat release. It was found that early injection timing leads to higher levels of pressure and temperature in the cylinder. Also, it was found that BMEP is more sensitive to equivalence ratio than to engine speed. Higher values of equivalence ratio lead to lower thermal efficiency even an increase in the value of BMEP was revealed. For medium engine speeds between 2000 and 3000, it was found that the optimum equivalence ratio is between 0.5 and 0.7. However, for low engine speeds the optimum equivalence ratio was around 0.35. For high engine speeds the thermal efficiency was almost independent of equivalence ratios higher than 0.4.