Online collaborative estimation technology for SOC and SOH of frequency regulation of a lead-carbon battery in a power system with a high proportion of renewable energy

In this paper, a collaborative online algorithm is proposed to estimate the state of charge (SOC) and state of health (SOH) of lead-carbon batteries that participate in frequency regulation of a power system with a high proportion of renewable energy. The algorithm addresses the inaccurate estimation of energy storage battery states caused by continuous and alternating charging and discharging over a short period. Analysis of lead-carbon battery chemistry and materials reveals that the resistance of the diaphragm is the most influential factor in battery aging. In addition, the hysteresis characteristics of an energy storage battery vary significantly between the charging and discharging stages. A second-order RC equivalent circuit model is proposed that considers the contact and diaphragm resistances, and hysteresis characteristics. Based on this, models for constant current charging interaction, constant voltage charging interaction, and dynamic discharging interaction are developed. The adaptive forgetting factor recursive leassquare (AFF-RLS) method is used to identify the parameters of the interactive models. Then an interactive multiple model with the embedded unscented Kalmanfilter (UKF) is used to estimate the SOC of the energy storage battery. The membrane and contact resistances identified by the interactive multi-model (IMM) are used to estimate the SOH, and online collaborative optimization of the SOC and SOH is achieved. The error of the proposed SOC estimation method is experimentally verified to be within 2%, which is less than 5% of the standard value, and the error of SOH estimation is within 0.5%, demonstrating the high accuracy of the proposed method.     

A Novel Recovery Strategy to Suppress Subsequent Commutation Failure in an LCC-Based HVDC

A subsequent commutation failure (SCF) can easily occur during the recovery process after a first commutation failure (1st CF). This paper analyzes the interaction mechanism of extinction angle, AC voltage, DC current and firing angle, and reveals that the complex coupling relationship during the dynamic process after the 1st CF has a significant effect on the SCF. The mathematical equations when considering different fault durations, fault severities and AC system strengths are then established. An AC fault voltage detection method based on reactive power and fault duration is also proposed to measure the fault severity, and an SCF inhibition control strategy (SCFICS) based on AC fault detection and reactive power control is subsequently proposed. This can not only inhibit the SCF, but also enhance the DC recovery speed effectively. Finally, based on the SCFICS, a simulation model is built, and the simulation results with different cases indicate that the SCFICS can effectively inhibit the SCF with good recovery performance, for three-phase-to-ground (TPG) and single-phase-to-ground faults, and with a fault inductance range of 0.01 H to 1 H.     

Multi-Resource Collaborative Service Restoration of a Distribution Network with Decentralized Hierarchical Droop Control

To improve the resilience of distribution networks (DNs) in the event of extreme natural disasters such as typhoons and rainstorms, it is imperative to efficiently implement distribution service restoration (DSR) to restore loads as soon as possible. In previous studies, DSR has mainly adopted the distributed resource model with droop or PQ control. This inhibits the exploitation of the potential of distributed generators (DGs) in load restoration when the DN loses support from the upstream transmission network. Thus, this paper proposes a multi-resource collaborative service restoration (MRCSR) approach for DNs incorporating local soft open points, DGs, and tie switches. The MRCSR model is developed by integrating a decentralized hierarchical droop control (DHDC) strategy and incorporating the frequency and voltage features of the load demand. A two-stage iterative feedback optimization (TSIFO) algorithm is then developed to analyze the MRCSR model in an accurate and efficient manner. Finally, the proposed model and algorithm are tested on the modified IEEE 33-bus system and a practical distribution system of the Taiwan Power Company to verify their effectiveness and advantages over existing approaches.     

System-defined design and performance of RFICs for W-CDMA mobile radio terminals

Third generation wideband CDMA (W-CDMA) systems like UMTS will add broad-band data to support video, Internet access, and other high speed services for untethered devices. They are currently deployed in Japan and will be introduced in Europe in 2002. Despite sufficient RF performance has been assumed in the standardization bodies, especially in mobile devices the RF part is still a limiting factor for the overall system characteristics. Only an integral design approach including both RF and baseband functionalities makes it possible to achieve analog front-ends with sufficient performance. This paper reviews transceiver architectures with respect to W-CDMA and presents some of the recent silicon-based radio frequency integrated circuits for mobile terminals.     

Single-ended time domain fault location based on transient signal measurements of transmission lines

Precise fault location plays an important role in the reliability of modern power systems. With the increasing penetration of renewable energy sources, the power system experiences a decrease in system inertia and alterations in steady-state characteristics following a fault occurrence. Most existing single-ended phasor domain methods assume a certain impedance of the remote-end system or consistent current phases at both ends. These problems present challenges to the applicability of conventional phasor-domain location methods. This paper presents a novel single-ended time domain fault location method for single-phase-to-ground faults, one which fully considers the distributed parameters of the line model. The fitting of transient signals in the time domain is realized to extract the instantaneous amplitude and phase. Then, to eliminate the error caused by assumptions of lumped series resistance in the Bergeron model, an improved numerical derivation is presented for the distributed parameter line model. The instantaneous symmetrical components are extracted for decoupling and inverse transformation of three-phase recording data. Based on the above, the equation of instantaneous phase constraint is established to effectively identify the fault location. The proposed location method reduces the negative effects of fault resistance and the uncertainty of remote end parameters when relying on one-terminal data for localization. Additionally, the proposed fault analysis methods have the ability to adapt to transient processes in power systems. Through comparisons with existing methods in three different systems, the fault position is correctly identified within an error of 1%. Also, the results are not affected by sampling rates, data windows, fault inception angles, and load conditions.     

Grouping-Based Optimal Design of Collector System Topology for a Large-Scale Offshore Wind Farm by Improved Simulated Annealing

During the construction of an offshore wind farm (OWF), the capital cost of the collector cable system accounts for a large proportion of the total cost. Consequently, the optimal design of the collector system topology (CST) is one of the most crucial tasks in OWF planning. However, for a large-scale OWF, the optimal design of CST is a complex integer programming problem with high-dimension variables and various constraints. Therefore, it is difficult to acquire a high-quality optimal design scheme. To address this issue, this paper proposes a new grouping-based optimal design of CST for a large-scale OWF. First, all the wind turbines are divided into multiple groups according to their geographical locations and the maximum allowed connected wind turbines by each cable. This not only reduces the optimization dimension and difficulty, but also effectively satisfies the ‘no cross’ constraint by putting the geographically closed wind turbines into the same group. Secondly, the electrical topology among different wind turbines in each group is initially generated by an improved dynamic minimum spanning tree (DMST). The division groups of the OWF are then adjusted to further reduce the capital cost by improved simulated annealing. To verify the proposed technique, comparison case studies are carried out with five algorithms on two different OWF.     

Effcient Location Updates for Continuous Queries over Moving Objects

The significant overhead related to frequent location updates from moving objects often results in poor performance. As most of the location updates do not affect the query results, the network bandwidth and the battery life of moving objects are wasted. Existing solutions propose lazy updates, but such techniques generally avoid only a small fraction of all unnecessary location updates because of their basic approach (e.g., safe regions, time or distance thresholds). Furthermore, most prior work focuses on...     

预倾角对液晶响应时间的影响

从理论上分析了预倾角对液晶动力学的影响,推导出一系列可用于描述预倾角非0条件下的液晶响应分析公式。使用垂直取向的液晶盒能够通过实验验证理论分析的正确性,这一发现将预倾角与液晶响应时间定量的联系在一起。对预倾角和液晶响应时间的关系的研究,将加深我们对液晶动力学过程的理解,从而有助于优化液晶的响应时间。从理论上分析了预倾角对液晶动力学的影响,推导出一系列可用于描述预倾角非0条件下的液晶响应分析公式。使用垂直取向的液晶盒能够通过实验验证理论分析的正确性,这一发现将预倾角与液晶响应时间定量的联系在一起。对预倾角和液晶响应时间的关系的研究,将加深我们对液晶动力学过程的理解,从而有助于优化液晶的响应时间。     

公共电极和反射器作互补的单盒式透反射型液晶显示器

给出了一种单盒式透反射型液晶显示器,它采用顶板公共电极和底板的反射器形成互补。这些狭长的公共电极和反射器在透射区域(T区)产生出强劲的纵向电场,而在反射区域(R区)带来微弱的边缘场。无论透射显示模式还是反射显示模式,均给出高的光学效率和良好的匹配灰度。     

Fine Domänen-Architektur zur Konfiguration einer wiederverwendbaren Software-Komponente

The development of new simulation applications within limits of time and constraints of budget is a challenging task. It has become difficult to understand, to code correctly and to maintain these new applications with traditional software development technology. Recently, techniques from the field of software engineering have been applied to achieve these tasks. To overcome the problem of handcoding which is susceptible to errors and time-consuming a domain architecture has been developed which combines object-oriented domain modelling and symbolically-assisted numeric computation.