浅谈农村灌溉期间低电压问题及预控措施

随着社会生产力的发展,电能逐渐成为农业生产中不可或缺的生产要素。农村在灌溉期间,灌溉负荷会在短时间内剧增,导致供电企业电压供电能量剧增。还容易出现低电压问题,线路过载和电压过低一方面会损坏供电设施,加快供电线路老化,还会烧坏水泵,因此灌溉期低电压成了急需解决的问题。     

窄视角蓝相液晶显示器

基于克尔效应的聚合物稳定蓝相液晶显示器被设计出窄视角显示模式,用于公共场所下私人信息的保护。通过使用几个简单的单轴膜,聚合物稳定蓝相液晶显示器就可以呈现出极佳的窄视角效果,即,对比度大于10°的可视区在20°极角范围内。此外,该显示器的驱动电压为14 V,最大透过率为71%,不仅满足了当前主流非晶硅薄膜晶体管的驱动需求,还进一步提高了背光源的光利用率。本文提出的窄视角蓝相液晶显示器与传统的窄视角模式相比较而言,没有复杂的电极结构以及繁琐的补偿方案,较3M公司的保护膜而言,具有生产成本低的优势,这些优势使其具备了在工业上生产的条件。在信息时代,窄视角液晶显示器将在防止私人信息的泄露上扮演越来越重要的作用。     

氧分压对铟镓锌氧薄膜晶体管性能影响

采用标准的液晶显示屏基板制备工艺制备出铟镓锌氧薄膜晶体管(IGZO-TFT),通过调节IGZO薄膜工艺中氧分压,研究不同氧分压对TFT器件电学性能的影响。实验结果表明,所有器件都展现出良好的电学特性,随着氧分压从10%增加到50%,TFT的阈值电压由0.5 V增加到2.2 V,而亚阈值摆幅没有发生变化。在栅极施加30 V偏压3600 s后,随着氧分压的增加,阈值电压向正向的漂移量由1 V增加到9 V。经过分析得出高氧分压的IGZO-TFT器件中载流子浓度低,建立相同导电能力的沟道时所需要栅极电压会更大,阈值电压会增加。而在金属-绝缘层-半导体(MIS)结构中低载流子浓度会导致有源层能带弯曲的部分包含更多与电子陷阱相同的能态,栅介质层(GI)会俘获更多的电子,造成阈值电压漂移量较大的现象。     

A harmonic injection SPWM method for the high-responsive PMSM control system

In a permanent magnet synchronous motor (PMSM) control system, usually, the phase voltage instruction is limited independently to prevent a three-phase pulse width modulation (PWM) wave from overflowing. This method decreases the efficiency of the bus voltage and causes voltage vector direction errors. To solve these problems, we propose a harmonic injection sinusoidal pulse-width modulation (SPWM). This method uses harmonic injected sinusoidal PWM to improve the utilisation ratio of the bus voltage, and consequently improve system performance. In this paper, we analyse the problem in terms of potential difference. The simulation results show that the proposed method can increase the utilisation ratio of the bus voltage up to 15.4%, and the voltage vector mode obtained with the proposed algorithm is larger than that obtained with the conventional one. The method with harmonic injection consequently improves current response, without affecting voltage vector accuracy. The experiment results validate the proposed method.     

Improving the open-circuit voltage of alkylthio-substituted photovoltaic polymers via post-oxidation

Molecular designing of photovoltaic polymers based on benzodithiophene (BDT) building blocks for high power conversion efficiency (PCE) in polymer solar cells (PSCs) arouse much attention in the past few years. To meliorate the energy levels of photovoltaic polymers featuring alkylthio substituted BDT units, a novel post-polymerization oxidation method was proposed applied in converting sulfur atom into sulfonyl group on side chains of the pristine polymer PBT-S. After treating with tiny amount of meta-chloroperoxybenzoic acid (m-CPBA) and hydrogen peroxide (H₂O₂), two batches of the target polymers, namely, PBT-SO₂-M and PBT-SO₂-H were prepared for the first time, respectively. The photochemical and electrochemical results indicate that both the HOMO levels are distinctly dropped with almost no influence on band gaps by introducing strong electron-withdrawing sulfonyl groups on side chains of BDT. Accordingly, the photovoltaic results reveal that the V_oc of devices based on PBT-SO₂-M and PBT-SO₂-H are 0.81, 0.71 V which are 0.17 and 0.07 V higher than that of pristine polymer PBT-S, respectively. Moreover, the J_sc and PCE of PBT-SO₂-H devices are comparable with those of the devices based on PBT-S. Overall, this work suggests that the molecular energy levels of D–A copolymers can be effectively tuned by a post-oxidation method.     

基于±800kV特高压直流输电线路典型故障分析

随着我国经济建设的不断完善,电力企业的发展越来越好,人民群众对供电的要求逐渐增多,既要满足供电的安全性,还要保证供电的持续性与稳定性,给电力企业的建设增加了很多的难度.±800kV特高压直流输电线路是一种新型的供电形式,凭借其输送容量大、线路损耗低等优势受到了电力企业的广泛关注.本文将针对±800kV特高压直流输电线路的典型故障进行分析.     

风电并网对电力系统暂态稳定的影响

随着社会经济的快速发展,作为一种重要的可再生资源,风力发电已成为当前发电技术最成熟、最具开发潜力的发电技术.在实际应用中,由于大规模开发风力资源、单一风电场装机容量不断提高,电网系统中风电占比日益增加.随着风电的不断接入,电网系统原潮流分布发生了变化,受风速随机与间歇性影响,其输出功率有一定的波动性,严重影响到电网电压的稳定.因此,在开发与规划风电场建设中,风电并网对电力系统电压稳定性的影响做深入研究,意义深远.     

高压电气试验过程的变压器应用研究

试验变压器为高压电气试验的有效开展提供了设备硬件基础,为实现对电网高压电气设备行状态的有效判断提供保障,本文针对高压电气试验过程的试验变压器的实际运用展开了研究,为进一步优化试验变压器的使用效果提供保障.     

110kV变电站电压互感器常见故障与处理措施

当前,由于许多因素的影响,导致110kV变电站在正常运行过程中仍存在不少问题,从而对电网供电安全产生了严重的影响,其中电压互感器故障是较为常见的问题.因此,本文就110kV变电站电压互感器常见故障与处理措施进行分析与探讨.     

Optimisation of sensing time and transmission time in cognitive radio-based smart grid networks

Cognitive radio (CR)-based smart grid (SG) networks have been widely recognised as emerging communication paradigms in power grids. However, a sufficient spectrum resource and reliability are two major challenges for real-time applications in CR-based SG networks. In this article, we study the traffic data collection problem. Based on the two-stage power pricing model, the power price is associated with the efficient received traffic data in a metre data management system (MDMS). In order to minimise the system power price, a wideband hybrid access strategy is proposed and analysed, to share the spectrum between the SG nodes and CR networks. The sensing time and transmission time are jointly optimised, while both the interference to primary users and the spectrum opportunity loss of secondary users are considered. Two algorithms are proposed to solve the joint optimisation problem. Simulation results show that the proposed joint optimisation algorithms outperform the fixed parameters (sensing time and transmission time) algorithms, and the power cost is reduced efficiently.