A highly efficient PV system using a series connection of DC–DC converter output with a photovoltaic panel

A photovoltaic (PV) power conditioning system (PCS) must have high conversion efficiency and low cost. Generally, a PV PCS uses either a single string converter or a multilevel module integrated converter (MIC). Each of these approaches has both advantages and disadvantages. For a high conversion efficiency and low cost PV module, a series connection of a module integrated DC–DC converter output with a photovoltaic panel was proposed. The output voltage of the PV panel is connected to the output capacitor of the fly-back converter. Thus, the converter output voltage is added to the output voltage of the PV panel. The isolated DC–DC converter generates only the difference voltage between the PV panel voltage and the required total output voltage. This method reduces the power level of the DC–DC converter and enhances energy conversion efficiency compared with a conventional DC–DC converter.     

光伏系统中的新型高增益直流升压变换器

针对光伏系统中对电压增益高、电压应力小的高性能直流升压变换器的需求,研究了一种新型高增益变换器的拓扑结构。首先,阐述了该变换器的结构来源,介绍了该变换器的工作原理,再推导其电压增益、开关管和二极管的电压应力公式,展示了部分元器件的电压、电流波形,并对比研究了该变换器与一些同类型的变换器的部分参数,最终通过开环试验验证了该变换器的有效性。该变换器具有一定的推广应用价值。     

液力变矩器的特性及其与发动机的匹配

本文介绍了液力变矩器的传动特点,分析了评价变矩器的基本性能参数及参数间的相互关系。阐述了变矩器选型的基本要求,并以装载机为例对液力变矩器与发动机的匹配应考虑的因素及匹配方法作了讨论。     

Soft switching bidirectional DC–DC converter for ultracapacitor–batteries interface

In this paper a new soft switching bidirectional DC–DC converter is introduced which can be applied as the interface circuit between ultracapacitors and batteries or fuel cells. All semiconductor devices in the proposed converter are soft switched while the control circuit remains PWM. Due to achieved soft switching condition, the energy conversion through the proposed converter is highly efficient. The proposed converter is analyzed and a prototype converter is implemented. The presented experimental results confirm the theoretical analysis.     

摩托车催化转化器性能台架评价试验研究

台架评价试验在摩托车催化转化器性能评价体系中起重要的作用。根据摩托车催化转化器的特点，参照汽车催化转化器台架评价试验方法，建立了摩托车催化转化器性能台架评价试验装置，用该装置进行了催化转化器空燃比特性，空速特性，温度特性，起燃时间特性等试验，为摩托车采用催化转化器提供了有效的技术支持和评价手段。     

New parallel driving strategy based on modified converters and peak current mode control for photovoltaic power generation systems

This paper proposes a modified converter for use in photovoltaic system. In the modified converter, the voltage ratio of output to input is equal to that of the general boost converter. The difference between the two converters is the configuration of output terminal. Therefore, the working voltage of an output capacitor and the value of its capacitance can be lower than those of the general boost converter. This paper also presents an efficient parallel driving scheme to increase output power and to reduce the output voltage ripple. The parallel driving method using the modified converter and current mode control gives a good solution for alleviating the current sharing unbalance problem. It reduces the output voltage ripple by increasing the equivalent switching frequency of the modified converter. The performance of the proposed converter system is verified through computer-aided simulations and experimental results.     

基于PXI技术的全功率风电变流器监测系统

在风力发电并网全功率变流器的研发过程中,为了测试和验证变流器的运行性能,需要一个变流器监测系统,不仅能够满足大量通道的高速数据采集,同时还要具有故障报警、录波、以及数据分析的能力。提出了并实现了一种基于PXI技术的3MW全功率变流器监测系统以满足上述的要求。详细描述了监测系统软硬件的实现方法,并且给出了大数据量监测系统的实时性问题的软件解决方法。在最后,给出了监测系统在3MW变流器实际调试过程中捕捉并记录下变流器故障的实例,表明了所提出的变流器监测系统的实效性。     

A new DC-link converter for induction motor drives

In this paper, a new DC link power converter is proposed for induction motor drives. It consists of a three-phase adjustable AC/DC power converter as a pre-stage, a three-active-switch power converter to simplify the conventional six-active-switch inverter and eliminate the lock-out time circuit and an adaptive DC-link voltage controller to achieve the optimal DC voltage and minimize the switching frequency of the three-active-switch power converter. The simple rotor-flux-oriented control can also be implemented easily using the proposed power converter to achieve high performance. Finally a prototype circuit is constructed and some experimental results are presented for demonstration     

镁质压渣剂在转炉炼钢过程中的开发和应用

为解决炼钢厂废弃镁碳砖难以在转炉炼钢过程中规模化全量应用的问题,研制了以废弃镁碳砖为材料的转炉压渣剂,能够有效降解转炉冶炼后期炉渣泡沫化的高度,增加炉渣的黏度,起到消泡的同时稠化转炉钢渣,实现快速倒炉倒渣（或者不倒渣）出钢的目的,对于提高炉渣的碱度和黏度,优化转炉后期的溅渣护炉工艺有积极的促进作用。     

直接驱动型全功率变流风力发电系统

从等效电路的角度分析了两级联H桥输出五电平的工作模式.为了满足直驱型风电系统对变流器的大功率要求,采用载波相移正弦脉宽调制技术(CPS-SPWM)控制级联H桥变流器,并对比了常规CPS-SPWM调制方法和对称调制法在实现五电平输出上的差异,经仿真和试验验证:这种拓扑结构满足直驱型风力发电系统对变流器的要求,说明CPS-SPWM调制方法适用于直驱型风力系统中的大功率变流器,在提高装置功率容量的同时,可以有效地减小变流器输出谐波,调节输出波形,提高整个装置的信号传输带宽.     

新型“冗余电转”调速器在大型灯泡贯流机组中的应用

针对目前水轮机调速器电液转换部件运行存在的问题,基于调速器调节性能最优和可靠性原则,综合考虑了位移型电转、流量型电转接口方式及控制切换,提出一种采用位移型电转+流量型电转不对称新型冗余方式设计调速器电液转换装置,有效避免了单一电液转换装置可能带来灵敏度不高或电转发卡问题。实例应用结果表明,采用该装置提高了调速器的性能及可靠性。     

定角控制高频MOSFET串联逆变器频率跟踪

针对采用功率MOSFET的高频串联型逆变电源,在分析其工作状态和传统锁相环对频率跟踪的基础上,提出了一种锁相电路与定角控制相结合的逆变器频率跟踪方法,实验结果表明该方法具有跟踪速度快,跟踪频率准确,保证逆变器始终工作在小感性状态,即逆变器始终工作在功率因数接近1的准谐振状态,从而提高了系统的功率因数,实现了MOSFET的软开关。     

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.     

一种具有零纹波输出的高增益耦合电感Boost变换器

为解决传统DC-DC变换器增益较低、电压应力较大等缺点,通过研究,以传统Boost变换器为基础,加入C-L-D倍压单元,并引入耦合电感倍压结构,提出一种具有零纹波输出特性的高升压变换器.变换器中C-D结构在进行倍压的同时还可作为钳位支路来吸收引入耦合电感所产生的漏感,减少器件的堆叠以降低成本,此外电容与输出电感形成的单...     

变频技术在泵与风机节能改造中的应用分析

某热电厂泵与风机等辅机上应用变频技术进行节能改造,取得年节电343.67万kWh的经济效益和较好的控制效果。用户应根据具体的管路特性曲线确定是否适用变频改造,并应了解一些使用变频器时的注意事项,以最大限度发挥变频器的作用。     

Battery-integrated boost converter utilizing distributed MPPT configuration for photovoltaic systems

In this paper, a battery-integrated boost converter utilizing the distributed maximum power point tracking (DMPPT) configuration for a photovoltaic (PV) system is studied. Each PV module has its own battery and DC/DC converter. Due to the proposed topology and use of battery, the MPPT function is not affected by the load demand and input power from PV. Application of the proposed converter to DMPPT configuration can save the voltage amplification stage and maintain PV voltage during partial shading. Steady-state analysis of the converter to determine the power flow equations is presented. Comparison with the series-connected conventional boost converter is reported in this paper. Simulation and experiment results of a laboratory prototype are presented to verify the effectiveness of the proposed approach. System design considerations are also discussed.     

Combined operation of DC isolated distribution and PV systems for supplying unbalanced AC loads

This paper describes a DC isolated network which is fed by distributed generation (DG) from photovoltaic (PV) renewable sources to supply unbalanced AC loads. The battery energy storage bank has been connected to the DC network via DC/DC converter called storage converter to control the network voltage and optimize the operation of the PV generation units. The PV units are connected to the DC network via its own DC/DC converter called PV converter to ensure the required power flow. The unbalanced AC loads are connected to the DC network via its own DC/AC converter called load converter without transformer. This paper proposes a novel control strategy for storage converter which has a DC voltage droop regulator. Also a novel control system based on Clarke and Park rotating frame has been proposed for load converters. In this paper, the proposed operation method is demonstrated by simulation of power transfer between PV units, unbalanced AC loads and battery units. The simulation results based on PSCAD/EMTDC software show that DC isolated distribution system including PV units can provide the balanced voltages to supply unbalanced AC loads.     

Methane emission from automobile equipped with three-way catalytic converter while driving

In this study, the hydrocarbon emission from a three-way catalytic converter with a gasoline engine was investigated experimentally. The results reveal that converters have lower catalytic oxidation activity for methane than the other hydrocarbons, and degradation of the catalyst with use results in a significant effect on methane emission. The maximum methane concentration in exhaust using a converter with 78,000 km use is about 100 ppm, which is 1.4 times that for a new converter. The light-off temperature of the catalytic converter for hydrocarbon oxidation also rises from 548 to 598 K with an increase in the operating age of catalytic converter from 0 to 78,000 km. The ratio of CH₄ concentration to total hydrocarbon increases with increasing vehicle speed and methane emission from the fuel of regular grade is higher than that of the premium grade.     

Comparison of control schemes for a fuel cell hybrid tramway integrating two dc/dc converters

This paper describes a comparative study of two control schemes for the energy management system of a hybrid tramway powered by a Polymer Electrolyte Membrane (PEM) Fuel Cell (FC) and an Ni-MH battery. The hybrid system was designed for a real surface tramway of 400 kW. It is composed of a PEM FC system with a unidirectional dc/dc boost converter (FC converter) and a rechargeable Ni-MH battery with a bidirectional dc/dc converter (battery converter), both of which are coupled to a traction dc bus. The PEM FC and Ni-MH battery models were designed from commercially available components.