双馈异步风力发电机组联网运行建模及其无功静态调节能力研究

受风速变动、电网运行方式变化等诸多因素影响,风电机组接入点电压有时波动很大.双馈异步风电机组通常采用功率因数cos? =1的恒定功率因数控制,而没有根据所接入电网运行要求来发挥其自身的无功调控潜能.本文建立了双馈异步风电机组的动态模型,以双馈异步发电机容量为约束条件,导出了双馈异步风电机组在不同风速下的无功功率调控能力,构建了面向接入点电压运行要求的风电机组无功功率调控策略,利用"电力系统综合分析程序"(PSASP)分析了某4.93万kW实际风电场采用所构建的无功控制策略抑制风速变化、电网运行方式变化等对接入点电压扰动的效果,仿真结果验证了所提出控制方法的有效性.     

一种改进的重复控制器在高频角振动转台中的应用

针对高频角振动转台在高频段跟踪周期信号的精度低问题,提出一种改进重复控制器设计方法。在重复控制的前项通道中引入可调增益,给出该系统稳定的条件以及控制器参数的确定方法,并论证了该方法的误差收敛和跟踪精度。仿真和实验表明,在高频段改进的重复控制器与PID控制器相比较,提高了转台正弦跟踪精度,改善了谐波失真度和高次谐波对转台角加速度的影响,同时也提高了系统的鲁棒稳定性。     

Fast‐scale bifurcation in power‐factor‐correction buck‐boost converters and effects of incompatible periodicities

In this paper, we derive the discrete‐time model for the power‐factor‐correction (PFC) buck‐boost converter in terms of a stroboscopic switching map. Fast‐scale instability is analysed through a fold diagram, which exposes the periodicity of the operation as well as the locations of the critical phase angles of the line voltage at which instability begins to occur along a half‐line cycle. The asymmetrical locations of the critical phase angles along a half‐line cycle is explained in terms of ‘under‐developed’ bifurcation. Border collision bifurcations are observed and analysed in detail. Copyright © 2006 John Wiley & Sons, Ltd.     

基于首行波曲率的柔性直流输电线路单端量保护

传统柔性直流输电线路行波保护存在高阻故障时灵敏度不足及拒动的问题.该文首先通过定量分析双极柔性直流输电线路故障时首行波在线路上的色散效应及在边界处的传播特性,推导了区内外故障首行波表达式,得到首行波弯曲程度与故障位置及过渡电阻的关系;其次,利用区内、外故障首行波曲率的显著差异构造故障识别判据,首行波解析式也为定值整定提...     

一种基于 DBSCAN 随机圆检测的多瓶口定位算法

现有医药灌封生产中的西林瓶瓶口定位方法易受瓶口边缘干扰的影响,导致瓶口圆中心定位不准确.对此,提出一种基于DBSCAN随机圆检测的多瓶口定位算法.首先,通过Canny边缘检测算法得到图像中所有轮廓,采用基于密度的DBSCAN聚类算法分割出感兴趣的瓶口边缘集;接着,针对每个单独的瓶口边缘集,采用最小二乘法和径向扫描获取瓶...     

基于小扰动的消弧线圈跟踪补偿性能验证方法

本文从消弧线圈不同档位下小扰动接地试验角度出发,建立了校验自动跟踪补偿消弧线圈装置性能的技术体系,提出分别在消弧线圈aa、bb、cc三个挡位下,进行小扰动单相高阻接地试验,其中aa档为自动跟踪补偿消弧线圈给出的控制挡位,bb档为aa档基础上降低2档,cc档为aa档基础上增加1档,若bb、cc挡位下的两次接地试验中,接地...     

采用国产变频器的ZJ90DB石油钻机电传动系统

本文叙述了ZJ90DB石油钻机电传动系统的配置与设计特点,将国产大功率变频器应用于ZJ90DB钻机电控系统之中,取得了成功,实现了国产化替代.同时对国产化变频器的发展进行了展望,对国产化电传动系统的进一步发展提出了建议.     

Fractionation and characterization of ɛ-poly-l-lysine from Streptomyces albulus CGMCC 1986

ɛ-Poly-l-lysine (ɛ-PLL) produced by Streptomyces albulus CGMCC 1986 was fractionated using ultra-filtration technique with 2 and 5 kDa cut-offs of membrane. The number-average molecular weight of each fraction was determined by ¹H nuclear magnetic resonance (NMR) method. The number-average molecular weights of the cutoffs of 5 and 2 kDa and the filtrate are 4,230.95, 3,687.80, and 1,900.82 Da, respectively. ¹H NMR indicates the chemical shifts of α-H, β-H, γ-H, δ-H, and ɛ-H are very similar to all the fractions. Fourier transform-infrared (FTIR) spectra showed that the ɛ-PLL solid samples obtained by freeze-drying at pH 5 with molecular weights higher than 2 kDa take on a β-turn conformation, however, the fraction with molecular weight smaller than 2 kDa adopts random coil structure. The antibacterial test proved that the fraction between 2 and 5 kDa of membranes behaves the highest antibacterial activity than other fractions for the test strains of Staphylococcus aureus, Micrococcus luteus, Bacillus subtilis, Escherichia coli, and Shigella.     

Mechanically strong conducting hydrogels with special double-network structure

Mechanically strong conducting hydrogels composed of poly(acrylamide) (PAAm) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been synthesized through the construction of a special double-network (sDN) structure. The novelty of the sDN hydrogels lies in the introduction of PEDOT-PSS semi-interpenetrating polymer network (semi-IPN) hydrogel as the second network. Based on the experimental results and the double-network theory, an additional strengthening effect resulting from the formation of the PEDOT clusters in a three-step fracture process is proposed. The applicability of as-prepared PAAm/PEDOT-PSS sDN hydrogels in electromechanical actuators is also briefly discussed.     

复杂环状柔直配电网单极断线故障特性分析

故障分析是制定保护方案的基础.环状柔性直流配电网不同位置发生单极断线故障后,部分正、负极电压/电流处于不平衡状态,危害系统的安全稳定运行,但目前对其研究较少.为此,对环状柔直配电网单极断线故障特性进行研究.首先,建立典型复杂环状柔直配电网模型,明确其中关键设备及各端口的协调控制策略.其次,通过建立故障前后系统等效模型,...