无线仓储管理系统的设计与实现

本系统以水电十三局仓储物流管理应用需求为核心,根据公司仓储运营模式的特性,利用条码、网络等技术,定制开发仓储物流管理软件及配套的数据采集器、平板软件,形成一套多终端开发的无线仓储系统解决方案,实现仓位的精确管理、科学可控的出入库管理以及全方位的数据查询统计功能,并通过数据库复制技术,实现仓储关键数据与公司原有综合项目管理系统数据的无缝对接。     

风电场多端直流系统应用研究

本文介绍了用于风电场组网的多端直流系统，研究了直流线路参数与系统稳定性的关系，并提出了一种网侧变流器的非线性PI控制方法。风电场多端直流系统由多个电压源变流器（VSC）并联组成，发电侧VSC控制风机向直流系统输送能量，再经网侧变流器并网。在不同控制模式下，需要在保证系统稳定性的前提下进行直流线路的参数匹配。本文根据小信号模型与大信号模型分别推导了稳定判据，并进行了仿真对比。本文利用以误差的非线性函数与传统PI环节构成的级联式控制器，实现了网侧变流器的高性能控制。仿真与实验表明该方法既提高了系统响应的快速性，又增强了抗扰能力。     

新型多端高压变换器拓扑构造和分析

提出一族多端高压变换器拓扑,分别为多端高压AC-DC变换器、多端高压DC-DC变换器、多端高压DCAC变换器和多端高压AC-AC变换器。论述了多端高压变换器拓扑的构造原理和主要拓扑结构。研究表明,所提拓扑的显著优点是一个拓扑即可实现多路输入或多路输出,大大减少了开关器件、降低了变换器成本,且输出多电平电压、谐波含量少,适用于多端高压直流输电、多端交流输电、多电机高压变频驱动、电力电子变压器、电能质量补偿装置等工业场合。     

多端柔性直流输电线路过电压抑制仿真

针对传统过电压抑制方法不适用于多端柔性直流输电线路,存在抑制效果不明显问题,提出多端柔性直流输电线路过电压抑制方法。以多端柔性直流输电线路的具体参数为依据,构建多端柔性直流输电线路模型,利用线路末端因数控制恒功率模式,实现多端柔性直流输电线路的稳态无功补偿,构建可控电抗器降压补偿系统,降低多端柔性直流输电线路的工频电压,在多端柔性直流输电线路中接入氧化物金属避雷器,完成输电线路的过电压抑制。为证明研究方法的过电压波动抑制性能较强,将所提方法与传统方法对比,实验结果证明上述方法的波动抑制性能优于传统输电线路过电压抑制方法,更适合应用于多端柔性直流输电线路的过电压控制中,为研究提供新的方向。     

Analysis and validation of wavelet transform based DC fault detection in HVDC system

Fault detection plays an important role in both conventional AC and upcoming DC power systems. This paper aims to study the application of discrete wavelet transform (WT) for detecting the DC fault in the high voltage DC (HVDC) system. The methods of choosing the mother wavelet suited for DC fault is presented, based on degree of correlation to the fault pattern and the time delay. The wavelet analysis is performed on a multi-terminal HVDC system, built in PSCAD/EMTDC software. Its performance is judged for critical parameter like the fault location, resistance and distance. The analysis is further extended to validation using results from experiment, which is obtained from a lab-scale DC hardware setup. Load change, one of the transient disturbances in power system, is carried out to understand the effectiveness of the wavelet transform to differentiate it from the DC fault. The noise in the experimental result gives rise to non-zero wavelet coefficient during the steady-state. This can be improved by removing the unwanted noise using right filter while still retaining the fault-induced transient. The wavelet transform is compared with short-time Fourier transform to highlight the issue with window size and noise.     

Instantaneous active and reactive powers in electrical network theory: A review of some properties

Research into electric power has been on-going since the end of the 19th century. The concepts of instantaneous active and reactive power are the result of the work carried out in the last few decades. In particular, they are used in the optimization of power systems, but they also form part of the general theory of electrical networks.Nevertheless, instantaneous active and reactive powers show noteworthy differences with other electrical powers. Here we review some of their properties and attempt to draw some conclusions that should be taken into account for their correct use. In particular we show the ambiguity of expressions such as “the branches of a network” or “the branches of a multi-terminal network” when these powers are involved.     

Distributed MPC for frequency regulation in multi-terminal HVDC grids

Multi-Terminal high voltage Direct Current (MTDC) transmission lines enable radial or meshed DC grid configurations to be used in electrical power networks, and in turn allow for significant flexibility in the development of future DC power networks. In this paper distributed MPC is proposed for providing Automatic Generation Control (AGC) in Alternating Current (AC) areas connected to MTDC grids. Additionally, a novel modal analysis technique is derived for the distributed MPC algorithm, which in turn can be used to determine the convergence and stability properties of the closed-loop system.     

Control strategies for automatic generation control over MTDC grids

Increasingly in power systems, there is a trend towards the sharing of reserves and integration of markets over wide areas in order to enable increased penetration of renewable sources in interconnected power systems. In this paper, a number of simple PI and gain based Model Predictive Control algorithms are proposed for Automatic Generation Control in AC areas connected to Multi-Terminal Direct Current grids. The paper discusses how this approach improves the sharing of secondary reserves and could assist in achieving EU energy targets for 2030 and beyond.     

基于动态相量法的改进多端模块化多电平换流器HVDC小干扰稳定模型

针对含多端模块化多电平换流器高压直流(MMC-HVDC)交直流混联系统的稳定问题,提出一种基于动态相量法的改进小干扰稳定分析模型。由于传统小干扰稳定模型均基于准稳态假定,因此难以反应电力电子型器件的快速动态过程。综合考虑多端MMC-HVDC有源及无源网络下的控制策略,推导并建立基于动态相量法的改进小干扰模型。建立含海上风电场的多端MMC-HVDC测试系统,并对比分析电磁暂态模型、传统小干扰模型及改进小干扰模型在动态响应下的精度及仿真时间。根据仿真结果,所提改进小干扰模型能够较好地跟随系统动态响应,预测系统振荡过程,并能显著削减仿真时间,其有效性和适应性得到了证明。