大准铁路接触网末端电压低的应对措施分析

根据实际运行中的部分接触网供电臂存在末端电压低的问题,提出一些适用可行的应对措施,能有效提高接触网供电臂末端电压,为电力机车的良好取流创造条件,更好地为铁路运输提供优质电源。     

高效重载码垛机器人末端执行器力学特性分析

目的为了提高码垛生产线的效率,实现高效重载码垛的功能,设计一种具有大负载能力的末端执行器。方法详细分析该末端执行器的结构设计及原理,并完成其三维模型的建立与设计。对快速定位机构、重载夹紧机构进行运动学分析及计算,并建立机构的运动学参数模型。利用ADAMS对不同楔块斜角的重载夹紧机构进行动力学仿真分析。结果获得了45°,30°,15°楔块斜角对应的楔块和顶板的力、位移、速度、加速度特性曲线;分析得知楔块斜角在15°左右时,末端执行器具有较好的力学特性。结论该末端执行器能够满足工作要求,对木板有较小的冲击破坏,能够提高码垛的效率及稳定性。     

牵引供电系统综合补偿技术的研究

为了保证电气化铁道牵引供电系统的功率因数、负序和谐波符合国家标准，本文以电气化铁道并联综合补偿和滤波理论为基础，通过理论分析，按照无功补偿为主，兼顾谐波治理和负序补偿的原则，提出一种有效的、性价比高补偿治理方案来实现综合补偿。理论分析TSC补偿装置对功率因数、负序和谐波兼有网压等供电质量指标有明显的改善，表明该装置符合我国国情、路情，对综合治理牵引供电系统的问题有益且可行。     

重载下逆变器三闭环控制策略研究

为解决传统双闭环控制逆变器在重载下掉压严重的问题,本文采用增加一个输出电压有效值反馈环的方法,使之形成三闭环控制系统。在分析三闭环控制原理的基础上,采用matlab搭建该系统模型,并进行了仿真实验。通过对比双闭环控制与三闭环控制仿真波形,相比于双闭环控制,三闭环控制更能有效解决逆变器在重载下掉压的问题。     

提高配网电压质量方法探究

配网在整个供电系统中占据非常重要的地位,配网电压质量关系到供电企业的供电服务水平,也关系到供电企业的经济效益,必须维护配网电压的科学稳定,提高配网电压质量。本文分析了配网电压指标以及提高配网电压质量的方法。     

低压网功率因数对供电企业的影响

对广大供电企业来说,用户功率因数的高低,直接关系到电力网中的功率损耗和电能损耗,关系到供电线路的电压损失和电压波动,而且关系到节约用电和整个供电区域的供电质量,这是众所周知的道理。文中简要集中探讨了影响电网功率因数的主要因素以及低压无功补偿的几种使用方法,以及确定无功补偿容量从而提高电力系统功率因数的一般方法。     

空调系统末端装置稳定性的仿真研究

建立了空调系统末端装置常见控制方式的仿真模型,尝试利用MATLAB仿真软件对空调系统末端装置的控制系统进行了仿真,通过对仿真曲线的分析,确定了末端装置控制系统从开始受到扰动到重新达到稳定所需的时间。这种方法对空调末端装置控制方式的选型具有一定的参考价值。     

浅议功率因数与供电效率的关系

在供电过程中,用户功率因数的高低。直接关系到电力网中的功率损耗和电能损耗,关系到供电线路的电压损失和电压波动,而且关系到节约电能和整个供电区域的供电质量。本文介绍影响电网功率因数的主要因素,以及低压无功补偿的几种实用方法。     

论电压无功控制装置在变电站中的应用及存在问题

结合多年的电网工作实践,对电压无功控制装置进行分析。电压无功控制装置可靠性高、运行稳定,有效提高电网供电质量,并能降低网损,总结了电压无功控制装置存在的不足之处。     

配网无功补偿分析

对配网线路运行特点进行调查,从理论上对无功补偿进行分析,通过控制无功补偿和电压优化,提出配网电力系统运行中的无功配置解决方案,为优质供电提供可靠保证。     

Design of reactive power compensators for distribution systems with harmonic distortion

Abstract

The objective of this paper is to derive a systematic algorithm to decide the optimal location and size of shunt capacitors and filters for distribution systems with harmonic distortion. In this paper, the problem of reactive power compensation is first formulated as a nonlinear programming of minimization of real power loss and capacitor cost under voltage constraint to decide the optimal locations and sizes of shunt capacitors. The harmonic load flow is then applied to solve the total voltage harmonic distortion factor (HDF). Finally, the tuning frequency of the single‐tuned filter and the capacity and voltage ratings of the corresponding reactor and capacitor are determined so that both the harmonic distortion and the reactive power compensation can be solved simultaneously. To demonstrate the performance and effectiveness of the proposed methodology, a practical distribution feeder with nine large industrial customers is selected for computer simulation. It is concluded that proper design of harmonic filters should be undertaken to solve the harmonic resonance problem, as well as the reactive power compensation for distribution systems with nonlinear loads.     

Optimal reactive power dispatch in a large power system with ac?dc and facts controllers

With the increased loading of existing power system, the problem of voltage stability and voltage collapse has become a major concern in power system planning and operation. The dependence of the system voltage profile on reactive power distribution forms the basis for reactive power optimisation. The technique attempts to utilises fully the reactive power sources in the system to improve the voltage profile and also to meet the reactive power requirements at the AC-DC terminals to facilitate the smooth operation of DC links. The method involves successive solution of steady-state power flows and optimisation of reactive power control variables with unified power flow controllers using linear programming technique. The proposed method has been tested on a real life equivalent 96-bus AC and a two terminal DC system.     

Scattered and reactive current, voltage, and power in circuits withnonsinusoidal waveforms and their compensation [power systems]

Properties of the current and power decomposition into the active, scattered and reactive components are discussed. The relative character of this decomposition is analyzed along with orthogonal decomposition of the load voltage. It is shown that this relative character emphasizes the change of the power flow with the cross section observed. The difference in the efficiency of the source apparent power compensation that can be obtained with a shunt and with a series compensator is emphasized. It is also shown that not only the reactive power Q _r, but also the scattered power D_s can be wholly compensated by a linear reactive compensator, so that the apparent power S of the load can be minimized to its active power P     

A novel method for evaluating the secondary voltages of transformers in primary substations based on sensitivity coefficients

This paper provides a novel method to evaluate the secondary voltage of transformers in primary substations. The method is focused on the secondary voltage deviation which is a function of real power, reactive power, tap position, and primary voltage of the transformer in transmission systems. It helps dispatchers calculate and predict voltage deviation before introducing voltage regulation and reactive power compensation. The proposed approach is first to derive the formula of secondary voltage sensitivity coefficients from power flow equations. Real operational data are then substituted into the formula to get sensitivity coefficients. Finally, the corresponding secondary voltage is calculated with the sensitivity coefficients obtained. Implementing historical data of three substations in the above algorithm shows that the errors between calculated and actual voltages are less than 0.15%. The proposed method can not only accurately estimate the secondary voltage of the primary substation, but also be used to calculate the compensating reactive power as well as determine the tap position of the transformer, thereby improving the voltage and reactive power control strategies of power transmission systems.     

Low-voltage superjunction technology

The scalability of superjunction and superfield power MOSFET technologies to breakdown voltage lower than 250 V is investigated. The influence of device geometry and process architecture on the switching figures-of-merit of these relatively new classes of power switches with a breakdown voltage rating of 80 V is presented. The current flow and field distributions inside these devices are described. Using Gauss's law, the field-induced compensation of the doping density in the drift region during the blocking state of both superjunction and superfield MOSFETs is calculated from the knowledge of the lateral field distributions. It is shown that the problem associated with imperfect charge compensation at the edge of the die for a superfield effect power MOSFET structure can be avoided by using an unconventional racetrack layout design.     

一种宽频率交流高电压校准装置

介绍了一种宽频率交流高电压校准装置.主要由变频稳压电源、升压变压器、宽频电容分压器和补偿电抗器组成.     

A multi-objective GRASP procedure for reactive power compensation planning

A multi-objective approach based on the GRASP (Greedy Randomized Adaptive Search Procedure) meta-heuristic is proposed to provide decision support in the problem of locating and sizing capacitors for reactive power compensation in electrical radial distribution networks. The installation of capacitors (local sources of reactive power) in the network is aimed at correcting the power factor to improve the quality of service, particularly the network voltage profile, and reduce energy losses and power peak. The mathematical model explicitly considers two conflicting objective functions: the minimization of the network active losses and the minimization of the capacitor installation cost. An algorithmic approach based on GRASP is presented for the characterization of the non-dominated solution set.     

Synchronous generator third-order model parameter estimation using online experimental data

A method to estimate the dynamic parameters of the commonly used third-order d-q model of a synchronous generator, based on measured electrical power, reactive power, terminal voltage, field current, field voltage and rotor angle following a small perturbation of the field voltage, is described. The parameters are estimated from two newly developed nonlinear functions for electrical power and terminal voltage by using a nonlinear least squares (NLS) algorithm. Results of simulation studies and experimental data collected from an 80 MVA, 10.5 kV generator show the efficacy of the proposed method and also reveal that the proposed method is valid for a wide range of operating conditions. For cases where rotor angle is not available, a new method for rotor angle estimation is also proposed.     

Harmonic and reactive power compensation as ancillary services in inverter-based distributed generation

The introduction of distributed generation, DG, into low-voltage (LV) networks opens up the possibility of supplying ancillary services to aid network management and to maintain power quality. DG itself can cause voltage magnitude difficulties when injecting real power into networks with high R/X ratios, but control of reactive power injection can help overcome this. Continuous control and support only at the voltage limit conditions (to avoid unnecessary reactive power flows in normal conditions) are explored. Relatively high-impedance LV networks are prone to harmonic distortion from nonlinear loads. A variety of control methods that emphasise either harmonic-line flows or local-voltage distortion are examined, and a compromise method based on resistance emulation is shown to be effective. Experimental results from a single-phase laboratory network and 2 kVA inverter are used to illustrate how these additional control functions can be integrated into the existing control scheme for real-power management. Decomposition of observed voltages and currents into harmonic terms that are phasesynchronised to the grid voltage is a challenge in real-time systems. Kalman observers are used to achieve this with an additional advantage of avoiding explicit phase-locking while producing quadrature components useful in instantaneous calculation of reactive power and in providing feed-forward compensation terms     

用于油气勘探的电代油驱动装置系统设计与分析

为满足碳中和背景下油气勘探企业对清洁、经济、高可靠性生产的需求,设计了基于双兆瓦级交流异步电动机变频调速的新型电代油驱动装置。采用模块化思想,设计了高压变电、低压传动分体模块箱式结构,提高了电代油驱动装置调度使用的便捷性,其中高压变电模块采用十二脉整流变压器,实现了在变频器成本无显著增加的前提下仅变压器成本增加25%,大幅节省了无功补偿成本,尤其是在场用电占比低的大功率钻进段,该装置的实测功率因数达0.95以上。针对双电机协同控制可能存在负荷不均衡的问题,设计了基于主从控制结构的PLC(programmable logic controller,可编程逻辑控制器)控制系统,并采用转速匹配控制结合变频器下垂控制的方法,实现了将电机转速偏差控制在10%以内;同时,所设计的控制系统支持多地操作以及现场数据远程监控,提高了电代油驱动装置的可靠性。试运行结果表明,所设计的电代油驱动装置满足实际工程需求,相较于传统柴油驱动装置,每月可节省52%的成本和减少27%的二氧化碳(CO₂)排放。所设计的装置在油气勘探节能领域具有一定的实用价值。