直流微电网微电源接口分析与控制策略设计

多数分布式电源发出的电能需要通过整流逆变后接入交流微电网,增加了电力电子器件的使用,降低了能量转换效率。介绍了更适合直流微电源和高频交流微电源接入的直流微电网拓扑结构,分析了交流微电源、直流微电源、储能装置与直流微电网间的电力电子接口,设计了以上接口的控制器,提出了整个直流微电网的控制策略。在Matlab／Simulink中建立上述直流微电网仿真模型,仿真结果表明,所建立的电力电子接口的正确性和所提出的控制策略的有效性。     

提高转炉煤气回收量的研究和实践

通过对转炉煤气回收、储存、输送系统和操作等方面进行优化控制,使转炉煤气回收率大幅度提高,产生较好的经济效益,为公司节能降耗做出贡献。     

High voltage step-up integrated double Boost–Sepic DC–DC converter for fuel-cell and photovoltaic applications

In this paper, an integrated double boost SEPIC (IDBS) converter is proposed as a high step-up converter. The proposed converter utilizes a single controlled power switch and two inductors and is able to provide high voltage gain without extreme switch duty-cycle. The two inductors can be coupled into one core for reducing the input current ripple without affecting the basic DC characteristic of the converter. Moreover, the voltage stresses across all the semiconductors are less than half of the output voltage. The reduced voltage stress across the power switch enables the use of a lower voltage and R_DS-ON MOSFET switch, which will further reduce the conduction losses. Whereas, the low voltage stress across the diodes allows the use of Schottky rectifiers for alleviating the reverse-recovery current problem, leading to a further reduction in the switching and conduction losses. A detailed circuit analysis is performed to derive the design equations. A design example for a 100-W/240 V_dc with 24 V_dc input voltage is provided. The feasibility of the converter is confirmed with results obtained from simulation and an experimental prototype.     

Single-switch boost-buck DC-DC converter for industrial fuel cell and photovoltaics applications

The realization of dc-dc converters performs a vital function in exploiting renewable energy sources such as solar photovoltaic (PV) and fuel cell applications. This paper demonstrates a single-switch unidirectional buck-boost dc-dc converter for continuous power flow control, excluding the hybrid switched-capacitor. The proposed converter utilizes a limited number of passive components, only four diodes and three inductors required, in addition to six capacitors. The converter can operate at a wide input voltage range with continues input current. The converter has experimented under real-time conditions with 660 W PV system. The obtained efficiency ranges from 93% to 98%. Furthermore, the converter has interfaced with 550 W fuel cell operated under different fuel pressure. The realized efficiency ranges from 91% to 97%. The maximum measured inductance current ripple is limited to under 0.70 A in both scenarios, whereas 0.16 V is the maximum output voltage ripple.     

转炉炉口粘渣清理技术现状与发展方向

针对转炉炉口的粘渣清理的炼钢难题,从炉口粘渣清理专用设备、防粘渣技术、脱渣涂料与清渣方法4个方面介绍国内外有关转炉炉口粘渣清理的技术研究状况。     

Design and performance analysis of the three-level isolated DC-DC converter with the nanocyrstalline core transformer

In this study, an isolated three-level DC-DC converter is proposed for high power and high conversion ratio applications such as fuel cells. The proposed system consists of a single phase three-level inverter, a medium frequency transformer and a diode rectifier unit. In the proposed system, a DC supply voltage is converted to a medium frequency AC voltage via a three-level inverter instead of the conventional two-level inverter. Since the three-level inverter generates an AC waveform with multiple steps, lower voltage harmonics and lower EMI levels than conventional two-level inverter are achieved. Thus, the three-level inverter provides higher efficiency value. The medium frequency transformer enables high voltage conversion ratio and provides galvanic isolation as well. The output voltage of the medium frequency transformer is converted to the DC voltage and thus the DC-DC conversion is achieved. According to simulation and experimental results, it is seen that the proposed DC-DC converter structure provides higher power density and higher efficiency values than conventional system.     

三效催化转化器性能的劣化及其对策

本文详细分析了三效催化转化器的性能劣化机理，并提出了减缓劣化速度的对策。     

多输入双向DC-DC变换器在燃料电池系统的应用

针对一种应用于燃料电池电动汽车驱动系统的多输入三半桥双向DC-DC变换器,对燃料电池电动汽车系统的工作过程进行了描述,同时对多输入三半桥变换器的稳态特性和软开关条件进行了详细的理论分析。最后通过仿真和实验验证了多输入三半桥双向DC-DC变换器的性能。     

变频器常见故障分析

本文对变频器的故障进行了简要的分类分析，并分析引发变频器故障的外部因素。     

Analysis and comparative study of pulsating current of fuel cells by inverter load with different power converter topologies

Fuel cells are being increasingly used for stand alone and grid connected systems in wide range of applications due to their high efficiency and low emissions. Because of unregulated nature of fuel cell voltage a power conditioning unit, consisting of DC-DC converter and an inverter, is invariably used as an interface between the fuel cell and the load in a typical fuel cell system for ac applications. Major issues with the use of fuel cells for ac applications are the low frequency pulsating current propagation on to the fuel cell side and dynamic response to various loads during transient conditions. Low frequency pulsating currents are reported to affect reactant utilization, degrade the performance and life of fuel cells. These current ripples can be reduced by filters with passive elements having bulky inductor and capacitor in the dc-link between the fuel cell and the inverter but, it will add to the weight and cost. DC-DC converters of different configurations are being used in the power conditioning unit of fuel cell systems. These converters are operated at high frequencies and the filtering units of these converters have minimal effect on low frequency ripple. But, it is observed that different configurations of power conditioner with same filtering components perform differently for the low frequency current ripple of the inverter load by mitigating the power mismatch between load and source at the DC link. This paper investigates and compares the low frequency current ripple mitigation by cascaded converters with conventional push-pull and also with series connected converters in the power conditioning stage of fuel cell system for ac applications. Parameters such as peak switching currents, the percentage of peak to DC level of low frequency current ripple are analyzed using these conversion topologies in power conditioning unit. The analytical and simulation results related to the study are presented. Key results are verified with experimental work.     

Control strategies for a photovoltaic--Energy storage hybrid system

受光照,温度等自然条件影响,光伏电源输出有功功率具有较大的波动性.因此,本身既非恒压源又非恒流源的光伏电源并网运行时会产生一系列问题,如对电网冲击性大,需增加旋转备用容量,难以参与电网调度等.利用电池储能系统来控制有功功率输出,可以使平滑光伏电源功率波动成为可能.研究了光储联合发电系统的运行模式,提出了适用于光储联合发电系统的拓扑结构和控制策略,并对储能用功率转换系统(PCS)进行了分析和设计,最后基于某光伏电站的实际历史运行数据,对所提出的方案进行仿真研究,仿真结果验证了光储联合发电系统控制策略的有效性和可行性,为光储联合运行示范工程提供了一定的理论依据和有力借鉴.     

降低汽油机冷启动阶段有害排放的方法探讨

汽油机在一个测试循环的排放污染物总量中，大约有70%--80%的非甲烷碳氢化合物在汽油机冷启动阶段没有经催化转化而直接排入大气中，造成严重污染。经研究后发现。在某些适当的条件下，使用催化转化器可大幅度降低汽油机的冷启动排放污染物的数量，进而提出了一些可行的实用方案。     

Fuel-cell energy generation system based on the series-capacitor boost converter

This work introduces the development of a power-electronics customizable energy system for their application on renewable energy generation based on proton-exchange membrane fuel cells. The customizable energy system aims to regulate the output voltage from a fuel cell, which has a relatively low amplitude and wide range of variation, to a fixed voltage to feed a grid-tie inverter. The customizable energy system proposed is based on a dc-dc converter for which different configurations (topologies) are available, such as the traditional single-phase boost or the (interleaved) multi-phase boost. The dc-dc converter of the energy system is based on the series-capacitor boost converter, a recently proposed converter that has a similar configuration to the interleaved boost converter. This article shows that the series-capacitor boost topology offers benefits in the proposed application. An experimental prototype was developed and tested in order to demonstrate the advantages of the system proposed.     

Modular multi‐purpose pulse converter turbocharging system for four‐stroke diesel engines

This paper presents a novel turbocharging system applied to four‐stroke diesel engines, which is named modular multi‐purpose pulse converter (MMPC) turbocharging system. Two‐dimensional steady flow simulations of the MMPC turbocharging system are performed with STAR‐CD code. A one‐dimensional unsteady flow simulation code finite volume method and total variation diminishing (FVM–TVD) has been developed. Using FVM–TVD, flow predictions in the diesel engine 8L250Z are carried out in the unsteady state with the mixed pulse converter (MIXPC) turbocharging system and MMPC, respectively. It is found that the MMPC system is more capable of reducing flow interference and has less variation of the scavenging coefficients for all cylinders than the MIXPC system. To validate the prediction results, experiments of the diesel engine 8L250Z equipped with the pulse converter (PC) turbocharging system, the MIXPC and the MMPC turbocharging systems are carried out. Experimental results show that the MMPC makes exhaust gas temperature lower before turbine and at each cylinder head face than the PC and the MIXPC. A diesel engine 20VPA6BSTC was simulated on series adaptability of the MMPC system. The simulation results reveal that the MMPC turbocharging system could be applied to four‐stroke high‐power diesel engines that may have any number of cylinders and different firing orders. Copyright © 2007 John Wiley & Sons, Ltd.     

Fuel-cell power conversion system based on double dual topologies

This article describes (and demonstrates through experiments) the feasible implementation of a power conversion system designed for a Fuel Cell (FC) application in renewable energy generation. The system is designed to be powered by an FC stack, which output is a low (in amplitude) non-regulated dc voltage, with a relatively wide range of variation. The system must boost the voltage from the power source to an internal 200 V dc bus, while the final output voltage (after the inversion) must be provided at a level of 120 V ac. The main feature of the described system is that it is based on double-dual converters, a family of converters with several advantages such as automatic power balance and large voltage gain; this leads to a good performance and power quality. The system is based on a double dual boost converter to increase and regulate the dc-voltage, and a double dual buck converter, to invert the dc-voltage and provide an ac-voltage as output. The article shows the system's feasibility through theoretical analysis and provides experimental results with an FC stack. Experimental results are provided to demonstrate the feasibility of the proposed system.     

A new method for dynamic performance improvement of a hybrid power system by coordination of converter's controller

In this paper, a new strategy for modeling and controlling a hybrid power generation system that contains a fuel cell (FC) and super capacitor (SC) system is proposed. The main drawback of FC systems is its slow dynamic because the FC current slope must be limited in order to prevent fuel starvation problems and to improve its efficiency and lifetime. To overcome this slow dynamic and to improve dynamic performance, a new control strategy is proposed to combine FC system with SC system. The proposed control strategy can be also used for cold starting and different types of FC systems with different dynamics. The control strategy is capable of determining the desired FC power to prolong FC system lifetime and keeps the AC and DC voltages around its nominal value in transient event by supplying propulsion power and recuperating FC energy. The minimum SC system is computed in new method and used to meet the load demand to constraint the DC bus voltage and enhances power regulation under various active and reactive load conditions. Two different case studies are used to obtain the simulation results using MATLAB/SIMULINK to verify the validity of the proposed control strategy.     

PROFIBUS—DP网络在40t电弧炉项目中的应用

阐述了PROFIBUS—DP通信网络系统的工作原理、硬件配置,以及软件程序。讨论了PROFIBUS．DP在40t电弧炉项目中应用编程实例。最后介绍了采用PROFIBUS—DP网络系统的使用效果．     

双向CLLC谐振变换器研究现状与应用前景

双向CLLC谐振变换器是双向直流/直流（direct current, DC）变换器中一类重要拓扑,具有实现软开关频率范围宽、调压范围大、功率密度高等特点。本文从基本拓扑及工作原理、建模分析方法、控制策略和应用这几个方面,对双向CLLC谐振变换器的现有研究成果进行了总结,分析了现有的问题,并提出了未来研究重点。结论表明,双向CLLC谐振变换器仍处于关键技术研究和小容量样机试验阶段,其在储能领域具有广阔的应用前景,是高压大容量双向变换器拓扑的重要发展方向。     

变流器模块损坏原因分析及对策

变流器作为风机的重要部件,对机组的安伞稳定经济运行有着重要的意义.本文介绍了风变电流器的现状、市场趋势以及SWITCH变流器的特点,并针对风电场全功率变流器实际运行中的主要故障进行了分析,给出了相关的应对措施.