稳定风电输出功率的控制策略研究

为稳定风电系统输出功率,提出一种在变流器的直流侧加入超级电容器(EDLC)储能的新拓扑结构,通过分析全功率双脉宽调制交-直-交变流器的控制策略,基于永磁直驱风电机组与电网连接的拓扑结构,提出超级电容器储能系统稳定风电系统输出功率的控制策略和输出功率的解耦控制方法,分析了风电系统输出功率初始值和超级电容器容量对输出功率稳定性的影响,并针对典型风速变化给出了输出功率初始值与超级电容器容量的整定范围。     

基于空间矢量PWM的多电平NPC功率变流器电压平衡控制

传统NPC拓扑受到直流中性点上电压不平衡的影响,不仅导致系统不稳定,还会影响电容器和半导体器件的额定值,增加总功率损耗。基于此,提出了一种适用于单相三线配电系统的新型变流器拓扑结构及其控制策略。所提变流器为中性点箝位（NPC）的H桥。为了解决基于NPC的变换器直流端口电容电压平衡问题,还提出了一种基于空间矢量PWM的直流端口电压平衡方法来平衡中性点电压,该方法充分考虑了输出电压的谐波影响和开关损耗,还定义了所应用的矢量序列。最后,通过与传统变流器进行仿真比较,以验证变流器在平衡和不平衡负载情况下的开关损耗的优越性。此外,还进行了实验验证,结果验证了所提电压平衡方法的有效性和优越性。     

基于氧化钨和普鲁士蓝的可变色超级电容器

氧化钨(WO3)薄膜作为阴极电致变色材料,还原态(阳离子嵌入)时着色而氧化态(阳离子脱出)时褪色;而普鲁士蓝(Prussian blue,PB)薄膜作为阳极电致变色材料,还原态(阳离子嵌入)时褪色而氧化态(阳离子脱出)时着色.利用不同离子存储状态下WO3和PB薄膜的变色互补性,构筑了基于WO3和PB薄膜的可变色超级电容器.利用脉冲激光沉积法和电沉积法在透明导电玻璃表面制备了 WO3/PB复合薄膜,并以该复合薄膜为电极,构筑了对称型可变色超级电容器.结果表明,WO3/PB复合薄膜具有优异的循环稳定性,循环200圈后,面电容量的保持率可达83.8％;在650 nm时,由于WO3和PB薄膜在不同电压下的协同变色,超级电容器的光透过率差在完全着色与褪色时为53.2％.该超级电容器在不同充、放电状态下可清晰地显示不同的颜色组合及光对比度,从而实现利用颜色变化指示超级电容器的能量存储状态.本研究有助于推动电致变色和能量存储领域的交叉融合,为超级电容器能量存储状态的可视化提供实验依据.     

储能双向变流器主电路参数设计及控制策略研究

设计了一种适用于电化学储能系统的双向变流器,采用一级变换主电路拓扑结构,交流侧采用LCL滤波器,减少注入电网的谐波,直流侧采用CL滤波器,降低电池侧纹波;介绍了储能双向变流器的工作原理,给出了交流侧LCL滤波器与直流侧CL滤波器设计原则,推导出基于LCL滤波器主电路数学模型,并设计了闭环控制系统。通过仿真和试验表明,该双向变流器主电路参数设计合理,电流谐波小,直流侧纹波小,可满足大容量储能系统的工作要求。     

含变流环节损耗的并网双馈感应电机潮流建模

提出基于机组潮流的背靠背变流器与直流电容有功损耗算法。将背靠背变流器、直流环节、感应电机与电网潮流方程联立,提出并统一求解计及变流环节的双馈感应电机(DFIG)并网潮流模型。通过与并网DFIG潮流模型计算结果对比,发现加入变流环节可使DFIG内部电压降低,绕组损耗减小,其效果随风速增加而明显,结果验证了所提算法模型的有效性。     

基于无直流储能元件小型直驱风力发电系统的一种新型PWM算法

为简化系统结构及减小变流器体积,采用一种新型小型直驱风力发电系统结构,系统发电机侧以电流源形式提供能量,且变流器直流环节无储能电感及电容。由于中间无直流储能环节,直流侧电流波动较大,如何在直流电流波动大的情况下保证并网电流波形正弦及对幅值的控制,是系统控制的关键及难点。通过分析该系统的运行特性,提出一种新型PWM算法,并基于此提出一种动态控制策略,搭建了系统仿真模型。仿真结果表明,应用所提出的PWM算法及控制策略,系统能够很好地实现对并网电流波形及幅值的控制。     

超大容量电容器在内燃机车起动中的应用

电容是一种储能元件,传统电容器电容量很小,随着科技的进步,一种超大容量电容器已在北京金正平科技有限公司科技人员的努力下研制成功,并投人批量生产.这种电容器电容量从几法拉到几百法拉,工作电压从十几伏到几百伏,放电电流可高达几千安培,能量密度比传统电容器高近百倍,放电功率比蓄电池高十倍.     

不拆引线测量电容器并联电阻方法的研究

指出使用自放电法或万用表来检测单体电容器并联电阻的局限性,介绍了一种针对并联电容器组不拆线测量单体电容器的电容量及并联电阻的方法,阐述了所研制仪器的原理和应用。     

用于并网分布式发电的九电平T型变流器分析

本文介绍了一种基于新型高效九电平T型变流器(9L-T²C),提出的9L-T²C在所需的有源开关和电容数量、6个飞跨电容(FC)额定电压和效率方面优于其他常见的直流链路九电平转换器。每个阶段只需要17个电源开关、8个栅极驱动器和2个FC。利用现有的极点冗余状态,开发了一种FC平衡算法,以稳定两个具有同样电压传感器的FC在稳态和动态的运行。此外,提出了一种有效的平衡方法,无需进一步冗余状态和集成到FC平衡直流链电容器。在相位配置脉宽调制(PD-PWM)方法中集成了功率因数和直流链平衡,消除了额外控制器的需求。对设计的PD-PWM方法,进行了数学分析,以建立18个功率因数的大小和所需的纹波之间的关系。通过与其他转化器的综合比较,论证了9L-T²C变流器的优点和应用领域。通过仿真研究和实验装置验证了所提出的9L-T²C电容器平衡方案在独立并网运行中的有效性。     

无源网络接入B2B型MMC-HVDC的Lyapunov控制策略研究

模块化多电平变流器（MMC）用于高压直流输电（HVDC）系统中时,通常采用PI控制方法,但这种策略存在参数选取繁杂、动态性能较差的缺点。为了提高高压直流输电（HVDC）系统的动态性能、简化参数选取,提出背靠背（B2B）型模块化多电平变流器-高压直流输电（MMC-HVDC）系统的Lyapunov控制策略。首先,建立B2B型MMC-HVDC数学模型;然后,设计Lyapunov函数控制策略;其次,在控制部分加入环流抑制、移相载波调制等,以完整地实现系统功能;最后,在Matlab/Simulink平台上验证了Lyapunov控制策略具有参数选择容易、动态性能优良的特点。     

直流供电系统电容在线测量器的设计与应用

为了测量直流供电系统接地电容,避免直流接地电容对系统带来的潜在危害,同时在不断电的情况下对系统接地电容进行测量,设计了一款直流供电系统电容在线测量器。其使用检测桥来进行系统接地电容的计算,通过切换检测桥来改变直流系统的正负极接地电压,使接地电容完成充放电过程,并记录充放电曲线。再通过一阶电路响应公式,来计算系统的等效接地电容。通过实验测试,该测量器能够准确测量系统的接地电容,测量误差在10%以内,且测量过程中不会对直流系统造成不利影响。     

水平管内两相流动网丝电容层析成像

1引言过程层析成像技术以两相流为主要研究对象[1],利用两相之间的物理性质的不同来确定两相流的相分布,达到成像的目的。实际工业过程考虑到安全性、经济性及速度的要求,电学层析成像技术成为首选方案,主要包括电阻过程层析成像(ERT)及电容过程层析成像(ECT)。非介入式的ERT和     

Transient analysis of a PV power generator charging a capacitor for measurement of the I–V characteristics

Measuring the I–V characteristics is of high importance since it can be considered as a quality and performance certificate for each PV generator. The most precise and inexpensive measuring method is represented in capacitor charging by the PV generator. Using the equivalent circuit of the PV generator with a capacitor as load and applying transient analysis on the circuit, we obtain the capacitor charging voltage and current as a function of time, as well as their differentials as a function of short circuit current and capacitor size. The derived equations facilitate the calculation of proper capacitance size for measuring the I–V characteristics, and considers the acquisition speed of the measuring system as demonstrated through two measurement samples in this paper. The capacitor size is directly and indirectly proportional to the short circuit current and open circuit voltage of the PV generator, respectively. Accordingly, the paper presents a capacitance calculation chart, which enables selecting the correct capacitance for measuring the I–V characteristics by a computerized data acquisition system.     

Analysis of electrodes matching for asymmetric electrochemical capacitor

Asymmetric electrochemical capacitor was categorized into two types: a battery-type electrode|capacitor-type electrode capacitor and a capacitor-type electrode|capacitor-type electrode capacitor. When designing asymmetric electrochemical capacitor, the influences of both current density and the electrode's potential window were taken into account. This article analyzed how the mass ratio between two electrodes influenced the electrochemical performances of asymmetric electrochemical capacitor. The formulas describing capacitor performance parameters (work voltage, specific capacitance, energy density and power density) were derived and applied to two types of asymmetric electrochemical capacitors. Therefore, the concrete relationships between mass ratio of electrodes and capacitor parameters were obtained. The influence of current density on mass ratio was investigated with organic LiMn₂O₄/AC system and others.     

风电变流器电容部件散热分析及仿真优化

针对某1.5 MW Freqcon变流器的电容系统的散热问题,建立了几何结构模型,在热分析理论的基础上,采用ICEPAK软件,对存在问题的电容冷却系统的温度场、速度场进行了三维仿真分析。研究发现在柜体最上端和最下端存在涡流区域,导致电容系统散热性能降低。为解决问题,提出了两种优化方案,并进行了比较分析,最后将方案二应用到实际运行中,结果表明:方案一去掉产生涡流部分的风道,可以在一定程度上减少涡流区域产生。方案二在方案一的基础上,利用ICEPAK的优化功能,优化参数,得出优化的最小风量为0.408m3/s,并且在该风量下电容器表面传热系数较高。实际运行结果与方案二模拟结果基本一致,并为风电变流器实际运行中的风道优化和电容散热提供一定的参考。     

Improved low‐temperature performance of novel asymmetric supercapacitor with capacitor/battery‐capacitor construction

A concept for designing capacitor/battery‐capacitor asymmetric supercapacitor is proposed to improve low‐temperature capacitance, which consists of a capacitor‐type electrode (C) and a capacitor/battery‐type composite electrode (NiO/C). This construction overcomes the capacitor‐battery asymmetric supercapacitor's shortcoming of losing capacitance characteristics. By adjusting the NiO/C mass ratio to 1/2, the new NiO/C–C asymmetric supercapacitor maintains excellent capacitance feature (rectangular CV curves and symmetrical charge/discharge profiles) as well as enlarging the work potential to 1.5 V, showing improved low‐temperature capacitance in comparison with C‐C and NiO‐C constructions. It is believed to come from the decreased total inner resistance and charge‐transfer resistance due to the substitution of NiO electrode with NiO/C composite electrode in the asymmetric supercapacitor. Copyright © 2016 John Wiley & Sons, Ltd.     

一种Buck变换器输出电容故障在线预测方法

提出一种基于特征参数退化的Buck变换器输出电容故障在线预测方法。首先,分析输出电容的失效机理,选取反映电容退化规律的等效串联电阻(ESR)RESR和电容值(C)为退化特征参数。然后,根据Buck连续导通模式,提出一种新的利用输出电压纹波分量计算特征参数ESR值RESR和C的在线提取方法,该方法可高效无电流传感器实现ESR值RESR和电容C在线监测。最后,利用特征参数ESR值RESR和C的时间序列,采用最小二乘支持向量机、BP神经网络和灰色模型实现Buck变换器输出电容故障值预测。仿真实例及试验验证该方法的有效性和准确性。     

Synthesis and pseudocapacitive studies of composite films of polyaniline and manganese oxide nanoparticles

We report the synthesis and pseudocapacitive studies of a composite film (PANI-ND-MnO₂) of polyaniline (PANI) and manganese oxide (MnO₂) nanoparticles. To enhance the interaction of MnO₂ and PANI, the surfaces of MnO₂ nanoparticles were modified by a silane coupling reagent, triethoxysilylmethyl N-substituted aniline (ND42). The composite film was obtained via controlled electro-co-polymerization of aniline and N-substituted aniline grafted on surfaces of MnO₂ nanoparticles (ND-MnO₂) on a carbon cloth in a electrolyte of 0.5 M H₂SO₄ and 0.6 M (NaPO₃)₆. In comparison to similarly prepared PANI film, the incorporation of MnO₂ nanoparticles substantially increases the effective surface area of the film by reducing the size of rod-like PANI aggregates and avoiding the entanglement of these PANI nanorods. Significantly, we observed significant enhancement of specific capacitance in PANI-ND-MnO₂ film compared to PANI-MnO₂ film prepared in a similar condition, indicating that the presence of the coupling reagent can improve the electrochemical performance of PANI composite film. A symmetric model capacitor has been fabricated by using two PANI-ND-MnO₂ nanocomposite films as electrodes. The PANI-ND-MnO₂ capacitor showed an average specific capacitance of ∼80 F g⁻¹ and a stable coulombic efficiency of ∼98% over 1000 cycles. The results demonstrated that PANI-ND-MnO₂ nanocomposites are promising materials for supercapacitor electrode and the importance of designing and manipulating the interaction between PANI and MnO₂ for fundamentally improving capacitive properties.     

Blade pitch control malfunction simulation in a wind energy conversion system with MPC five-level converter

This paper is on a wind energy conversion system simulation of a transient analysis due to a blade pitch control malfunction. The aim of the transient analysis is the study of the behavior of a back-to-back multiple point clamped five-level full-power converter implemented in a wind energy conversion system equipped with a permanent magnet synchronous generator. An alternate current link connects the system to the grid. The drive train is modeled by a three-mass model in order to simulate the dynamic effect of the wind on the tower. The control strategy is based on fractional-order control. Unbalance voltages in the DC-link capacitors are lessen due to the control strategy, balancing the capacitor banks voltages by a selection of the output voltage vectors. Simulation studies are carried out to evaluate not only the system behavior, but also the quality of the energy injected into the electric grid.     

Effect of conductive additives on electrochemical performance of Li4Ti5O12 in hybrid capacitor

将添加不同导电剂的钛酸锂负极与活性炭正极组装成混合电容器,研究了不同导电剂对混合电容器性能的影响。利用扫描电子显微镜表征了钛酸锂负极的表面形貌,采用LAND测试仪、电化学工作站对混合电容器的电化学性能进行测试分析,最终确定最佳的导电剂类型。实验表明,以super-P/VGCF为导电剂的混合电容器具有最佳的电化学特性,在0.1 A/g条件下,电容器的比容量达到45.4 F/g,在2 A/g时容量保持率为91.5%;在0.5 A/g条件下,经过10000次循环后,容量保持率为93.2%。