A Flexible Voltage Control Strategy Based on Stage-Division for Microgrids

The occurrence of power flow reversal and off-limit of the voltage on common bus becomes more frequent because of the increasing penetration of renewable energy sources (RES) in microgrids. To guarantee the safe and stable operation, adjusting the power output of RES-based inverters to avoid the off-limit voltage is necessary. Considering the apparent power characteristics of inverters, as well as the minimum participation of active power, a voltage control strategy based on stage division to be within the voltage limit is investigated in this paper. In the case of unknown demand and distribution of loads, the proposed control strategy is able to make full use of the apparent power to regulate voltage using simple calculations, while the performance in economical operation is satisfactory. Simulation results prove the effectiveness of the proposed method on the common bus off-limit voltage adjustment.     

Hochgenaue Abstandsmessung mit Mikrowellen

Using microwave technology for industrial sensing applications has the advantage of being insensitive to environmental influences. The presented near range radar has an accuracy of 0.1 mm. This high precision was achieved by using dynamic frequency divider chips for direct frequency measurement and a six-port for phase measurement at 35 GHz. A digital signal processor calculates the distance.     

Vergleich, Dimensionierung und Realisierung einphasiger Power Factor Correctors minimalen Realisierungsaufwands

In the future laws and restrictions will limit the amplitudes of the low frequency harmonics of mains currents of rectifier systems. While diode bridges are very simple, compact and cheap, their input current shows high low-order harmonics. In the past various rectifier systems have been developed that avoid low-order input current harmonics by means of active current control. The significantly reduced input filter results in a small and compact total rectifier system. In this paper different rectifier systems are discussed and compared. Since industry is interested in simple and cheap solutions the rectifier systems are discussed under these considerations. Besides an introduction of different power circuits and control schemes, the systematic choice of the power semiconductors is presented.     

包含负荷及系统动态的电力系统电压稳定仿真

本文提出一种对系统电压稳定进行详细仿真的方法，此方法考虑了系统及负荷动态的影响，诸如系统干扰、电动机力矩及滑差，变压器抽头的的换接、坚持Ｐ、Ｑ需要的负荷、抑制励磁以防止发电机过热，以及有电压偏移负反馈的ＳＶＣ等。由于是高阶次的非线性全模，作者采用一种既精确又快速的方法来进行积分，还应用了一种毋需经过亢介次矩阵求逆就可便捷地求解亢介次Ｊａｃｏｂｉ阵的方法。     

PhotoPrev：Unifying Context and Content Cues to Enhance Personal Photo Revisitation

Personal photo revisitation on smart phones is a common yet uneasy task for users due to the large volume of photos taken in daily life. Inspired by the human memory and its natural recall characterist...     

Hetero-DB：Next Generation High-Performance Database Systems by Best Utilizing Heterogeneous Computing and Storage Resources

With recent advancement on hardware technologies, new general-purpose high-performance devices have been widely adopted, such as the graphics processing unit (GPU) and solid state drive (SSD). GPU may ...     

Resource allocation for cognitive WLAN over fiber

In this paper,a novel WLAN system,Cognitive WLAN over Fiber (CWLANoF),is introduced in the first place.Moreover,when CWLANoF has more channels than STAs,a new channel allocation scheme is proposed using the Hungarian algorithm,which is demonstrated to be the optimal one.Furthermore,when CWLANoF has fewer channels than STAs,it is possible for more than one STA to share the same channel simultaneously based on the new features of CWLANoF.And the power control scheme is proposed for this kind of sharing,considering efficiency and fairness.Finally,extensive simulation results illustrate the significant performance improvement of the proposed channel allocation scheme and power control scheme.     

Communication ICs — market leaders in microelectronics

In recent years communication ICs became the fastest growing semiconductor market segment mainly driven by personal wireless communication products like pagers or mobile phones and internet applications with their permanent demand on increasing bandwidth. The high volume consumer market and its demand for low-cost, low-power, and highly integrated solutions had stimulated RF design engineers all over the world to develop novel integrated solutions for communication devices with an innovative advance that is more close to Moore’s law than it was in the past. This was made possible once by a great progress in semiconductor technology, where well established silicon and silicon bipolar technologies extend the operating range steadily up to higher frequencies in the GHz range at the expense of GaAs technology which is driven back to niche products like power amplifiers and to communication techniques in the 40-Gbits/s range and above. On the other hand the integration of a complete system with a single technology has also consequences to the topology of the system and that has led to fundamental changes in system design procedures, which are treated by more sophisticated design tools which cover both system and circuit design and bring them close together. In this paper some actual trends in the development of communication ICs are presented and examples of recently published devices are given.     

光网络发展展望

光网络的具体含义到底是什么，这是一个仁者见仁，智者见智的问题。但有一点是取得了共识的，即未来的光网络应该是一个应用灵活、可靠、性能稳定的网络。它应该满足传输各种信号，如SDH、ATM、IP等的所有基本要求（即灵活性、可升级性和系统生存性应能独立于比特率和协议）。这样一个网络应该能够对各种信号进行有效的传输、调度、保护和管理。因此，如果我们希望能对光网络今后的发展做一点预测的话，必须综合考虑传输技术、光网络产品、光网络设计以及光标准研究等方面的发展情况，才能尽量避免偏颇。