A novel method of suppressing the inrush current of transformers by using a series‐connected voltage‐source PWM converter

This paper proposes a novel method of suppressing the inrush current of transformers. A small‐rated voltage‐source PWM converter is connected in series to the transformers through a matching transformer. As the connected PWM converter serves as a resistor for the source current, no inrush phenomena occurs. The required rating of the PWM converter, which serves as the damping resistor for the inrush phenomena, is 1/400 that of the main transformers in single‐phase circuits. In three‐phase circuits, it is 1/900. The basic principle of the proposed method is discussed. Digital computer simulation is implemented to confirm the validity and excellent practicability of the proposed method using the PSCAD/EMTDC. A prototype experimental model is constructed and tested. The experimental results demonstrate that the proposed method can perfectly suppress the inrush phenomena. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 157(4): 56–65, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20174     

Fishtail magnetization in single crystal Tl2Ba2CuO6

We report extensive magnetization measurements on single crystals of Tl₂Ba₂CuO₆ superconductors. The fishtail magnetization is found to disappear above a characteristic temperature (60 K), which corresponds to a crossover temperature in the temperature dependence of the irreversibility line. Since the low temperature irreversibility field can be modeled by a Josephson coupled layered system, we propose that the fishtail magnetization in the Tl₂Ba₂CuO₆ system is due to dimensional crossover.     

Dynamic anti-windup based control method for state constrained systems

Based on the dynamic anti-windup strategy, an alternative control methodology for state constrained systems is presented. The proposed method is an a posteriori approach for state constrained systems, which is differentiated from the usual a priori approach. That is, first a linear controller is designed to show a desirable nominal performance by ignoring state constraints. Then, an additional compensator is introduced to account for state constraints. By minimizing a reasonable performance index, a dynamic compensator is derived explicitly, which is expressed in plant and controller parameters. The proposed method not only provides a graceful performance degradation, but it also guarantees the total stability of the resulting systems. An illustrative example is given to show the effectiveness of the proposed method.     

CVT中阻尼器的研究

阐述了电容式电压互感器的各种阻尼器的优缺点,并对速饱和阻尼器设计进行了详述,提出了CVT设计速饱和阻尼器应注意的事项。     

用于MEMS器件的高性能运算放大器的IC设计与测试

根据特定电容式微传感器后续处理电路的高性能要求。设计一个运算放大器芯片，设计中采用了美国MOSIS公司提供的n阱0.35μm cmos工艺的SPICEBSIM3mos管模型。手算估计芯片的参数，然后采用了两种能系统反映芯片特性的测量电路对设计进行了性能测量。并根据测试结果对设计微出相应调整，从最终测试结果来看。设计的运算放大器具有很好的静态和动态性能。     

氯能谱测井仪的改进及其应用

对于高矿化度地区,一种改进的确定剩余油饱和度的测井仪已研制成功.它利用3He计数管测量热中子,BGO晶体替代NaI晶体,使得探测效率明显提高;在源室和BGO探测器之间加一屏蔽层,使得信噪比提高;双探测器同时测量热中子和次生中子伽马,双向差异解释方法有效地克服了地层骨架和泥质的影响,解释精度明显提高.     

茶溶液中饱和吸收产生热致非线性效应的研究

本利用单光束扫描法研究了在４８８ｎｍ波长下，一种花茶酒精溶液因饱和吸收所产生的热致非线性效应，测得其热光系数ｄｎ／ｄＴ为＝１．２×１０＾－５℃，饱和光强为５．４ＫＷ／ｃｍ＾２。     

折射率非线性调制的双重光纤光栅特性

利用耦合模理论 ,系统分析了双重光纤光栅在折射率深度调制或非线性调制情况下的光谱特性。结果发现 ,在折射率非线性调制情况下 ,双重光纤光栅具有规则的多波长反射特性 ,同时 ,其反射光谱中的二次谐波也变得非常强 ,因此 ,它是一种实现多通道波分复用器、分插复用器及多波长激光器等的潜在技术。