分布式阻抗末端加载的TEM喇叭天线设计

基于功率容量和口径匹配扩展低频工作带宽两方面的考虑,设计了一种具有分布式阻抗末端加载结构的超宽带TEM喇叭天线。首先,对渐变式同轴-平板的巴伦结构进行了优化设计,扩展了馈电结构的工作带宽,提高了馈电效率;其次,对指数型TEM喇叭天线末端进行了分布式阻抗的匹配设计,其端口特性和辐射特性均得到了明显改善,并采用功率方向图和能量方向图对天线的辐射效果进行评估。实验结果表明,相对于指数型TEM喇叭天线,加载分布式阻抗匹配末端结构后,天线低频带宽展宽了330 MHz,天线主轴辐射电场峰峰值提高了10%,馈电效率提高了17%。

单相供用电系统故障漏电电流特征及保护方法

为解决供用电系统和用电设备的正常漏电电流与故障漏电电流的保护和识别问题,首先针对供用电系统和用电设备的漏电特征进行分析,明确正常漏电与故障漏电的识别特征;其次分析高频电力电子设备的漏电电流特征,提出基于高频电流负反馈的磁调制漏电电流量测方法,实现故障漏电的准确检测与保护;最后提出基于漏电电流阻容特征的单相供用电系统的漏电保护策略,分别设置故障漏电动作阈值和正常漏电动作阈值,在保障供用电系统和用电设备正常运行的前提下实现故障漏电的准确保护。结果表明:正常漏电与故障漏电电流阻容特征不同;基于高频电流负反馈的磁调制漏电电流量测方法可以有效降低正常高频容性漏电电流的影响;基于漏电电流的阻容特征的漏电保护策略,可提高漏电保护的有效性和可靠性。

Design of a distributed power amplifier based on T-type matching networks

The impedance characteristics of distributed amplifiers are analyzed based on T-type matching networks, and a distributed power amplifier consisting of three gain cells is proposed. Non-uniform T-type matching networks are adopted to make the impedance of artificial transmission lines connected to the gate and drain change stage by stage gradually, which provides good impedance matching and improves the output power and efficiency. The measurement results show that the amplifier gives an average forward gain of 6 dB from 3 to 16. 5 GHz. In the desired band, the input return loss is typically less than - 9. 5 dB, and the output return loss is better than -8.5 dB. The output power at 1-dB gain compression point is from 3.6 to 10. 6 dBm in the band of 2 to 16 GHz while the power added efficiency （PAE） is from 2% to 12. 5% . The power consumption of the amplifier is 81 mW with a supply of 1.8 V, and the chip area is 0.91 mm × 0.45 mm.

Directional Overcurrent Relays Coordination Restoration by Reducing Minimum Fault Current Limiter Impedance

FCL （fault current limiter） is used to solve relays miscoordination problem arises from DG （distributed generation） installation. In most published researches, different optimization methods are developed to obtain optimal relay settings to achieve coordination in case of not installing DG, then depending on the achieved optimal obtained relay settings, FCL impedance is deduced to ensure relays coordination restoration in case of installing DG. Based on original optimal relay settings, obtained FCL impedance is not the minimum one required to achieve relay coordination. The contribution of this paper is the generation of multi sets of original relay settings that increase the possibility of finding FCL impedance of minimum value which is lower than the calculated value based on original optimal relay settings. The proposed method achieves better economic target by reducing FCL impedance. The proposed approach is implemented and tested on IEEE-39 bus test system.