兆瓦级双馈风力发电机转子励磁变频器输入电抗器参数选择的研究

针对兆瓦级双馈风力发电机转子励磁变频器的特点 ,本文首先将双PWM交 -直 -交变频器的主电路拓扑进行了等效 ,然后对等效后变频器的模型进行傅立叶分析 ,得出了系统的连续的高频数学模型。在此基础上 ,推导出了在一定的电流输入纹波系数的要求下 ,变频器输入电抗器参数的选择范围。进一步仿真的结果证明了本文所得出结论的正确性     

Electric power generation at the ebb tide

In this paper, a method is proposed to generate electric power from buoyancy and weight at the ebb tide. The proposed method can be applied anywhere with changing water level such as coast, dams and the upper reservoirs of pumped-storage plant. The dominant contribution of this research is that the power generation capacity in the off-peak period can be shifted to the peak period. In addition, the capital cost of the proposed method is lower than the traditional tidal power plant because a barrage is not required.     

溢流坝表孔弧形闸门流激振动原型观测研究

本文根据溢流坝弧形闸门的工作特点,对工作闸门的泄流流态、闸门结构的静动力特性以及流激振动响应等方面进行了系统观测研究。在静力特性观测研究的基础上,进行了闸门局部开启泄洪状态下的水力学和流激振动状态检测,取得了不同开度下溢流坝闸孔进口水流流态,揭示了大开度运行时门前涌浪对闸门面板下部结构的冲击作用。获得了闸门结构不同开度条件下典型部位的水流脉动压力作用以及振动加速度、动位移和动应力等动力响应参数的量级及其谱特征,取得了闸门振动量随开度的变化规律。对闸门结构的运行安全性进行分析评价和科学论证,提出了闸门结构局部开启的运行操作规程。     

含有分布式发电的配电网重构研究

分布式发电作为现有电力系统的有益补充,具有广阔的发展前景.分析了分布式发电并网对配电网重构问题的影响.在应用遗传算法时,采用了以网络中环路教为染色体长度,环路开关号为染色体基因的十进制编码策略,结合提出的三条禁忌规则,以纠正染色体不在可行解空间的问题;潮流算法采用以分布式发电为"负"负荷模型的前推回代法,更加符合配电网的实际情况.研究结果表明,对含有分布式电源的配网优化重构后,可在更大程度上减少网损,并对电压起到一定的支撑作用.最后对含有分布式发电的配网重构问题的未来研究方向进行了探讨.     

Improved ultraviolet second-harmonic generation at elevatedrepetition rates from a medium-scale copper-vapor laser

We report significant improvements in ultraviolet (UV) power generation at elevated pulse-repetition frequencies (10⩾kHz) from a frequency-doubled copper-vapor laser (CVL), employing a Ne-H₂ buffer gas. In particular, UV powers of 1.3 W and 0.6 W at 255 nm (SHG green) were generated at 10 kHz and 20 kHz, respectively, when using H ₂ additive in a medium scale (nominally 20 W) CVL oscillator. These results represent improvements of 6.5× and ~100×, respectively, over the UV powers obtained for pure neon-buffer gas. The enhanced UV powers are directly related to the improvement in high-beam quality extraction from the CVL due to the beneficial effects of the H ₂ add-gas on CVL gain characteristics     

超超临界燃煤发电技术是我国目前发展洁净煤发电技术的优先选择

超超临界燃煤发电技术是目前世界上成熟、先进、高效的发电技术。通过对几种主要的洁净煤发电技术的比较，配有污染物排放控制技术的超超临界燃煤发电机组在效率、容量、可靠性、设备投资及环保等方面都具有一定的优势。分析火电行业存在的主要问题，认为超超临界燃煤发电技术是我国目前发展洁净煤发电技术的优先选择。根据电力行业、发电设备制造业及相关行业的现有基础，指出我国已具备了发展超超临界燃煤发电技术的条件。     

Distribution voltage rise at dense photovoltaic generation area and its suppression by SVC

An SVC is proposed as a reactive power compensation device to suppress the rise in the customer voltage due to photovoltaic power generation systems. The SVC produces a reactive power by controlling a thyristor. The effect of the SVC on the rise in the customer voltage has been investigated. Calculation results show that installing an SVC on the low‐voltage side is more effective for suppressing the rise in the customer voltage compared to an SVC located on the high‐voltage side. As far as the calculation conditions are concerned, it is found that the rated capacity of the SVC needed to maintain the customer voltage within 101±6V is over ±11.1kVA. The slope reactance required to suppress the customer voltage lower than 107 V is found to be under 1.28%. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(2): 47–53, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20478     

Sensorless rotor position estimation at standstill of cylindrical brushless dc motors using opened phase voltage change caused by eddy currents

A rotor position estimation of a cylindrical brushless dc motor at standstill has been difficult to obtain. Therefore, torque control of a motor has been difficult at starting of the motor, and realization of the position estimation at standstill has been sought. This paper proposes a simple processing of a rotor for which nonmagnetic materials are pasted on the rotor surface. This processing generates an eddy current on nonmagnetic materials and causes an opened phase voltage change according to rotor position. The experimental results using a microcomputer show that it is possible to estimate rotor position of the cylindrical motor despite a standstill by using the opened phase voltage change. ©�1998 Scripta Technica, Electr Eng Jpn, 126(1): 52–60, 1999     

盘式开关磁阻电机临界重叠位置磁化曲线计算

针对三维有限元方法分析轴向磁场盘式开关磁阻电机时计算机配置要求高、耗时长及不适于电机的优化设计和基于定转子极中心线对齐位置和定子极中心线和转子槽中心线对齐位置这两个关键位置的磁路法计算精确度不高等问题,对转子齿前沿和定子齿前沿重叠位置即临界重叠位置处磁化曲线进行解析计算.利用三相6/4极和12/8极轴向磁场盘式开关磁阻电机的有限元仿真结果及磁阻最小原理划分该位置处磁链并进行计算,推导出该种电机临界重叠位置处磁化曲线,并与三维有限元方法的计算结果进行对比.分析结果表明,此种解析法的计算精确度符合要求.计算结果验证了解析分析计算的正确性.     

架空送电线路新旧导线混架时的弛度平衡与控制

针对架空送电线路同层横担上新旧导线混架时存在的问题,分析了新旧导线混架时新导线初伸长补偿的误区,提出了解决新旧导线混架时弛度不平衡的调整控制方法.