考虑大规模风电外送的半波长输电系统稳态电压控制方法

大规模可再生能源可以通过半波长输电线路实现远距离传输.本文针对考虑大规模风电外送场景的半波长传输系统提出了一种改进的稳态电压控制方法.首先,基于长线路分布参数模型推导出半波长线路特殊的电压分布规律.在二级电压控制层面,基于其电压特性,提出考虑对主导节点电压参考值跟踪的同时,通过限制半波长线路的无功传输实现对沿线稳态过电...     

低压智能电力电容器实用技术

介绍低压智能电力电容器的强大功能,并通过在企业中的实际应用,证明其无功跟踪补偿与调谐滤波的效果,可为企业减少电能损耗和电费开支,提高企业的经济效益.     

Analysis on the fault characteristics of three-phase short-circuit for half-wavelength AC transmission lines

Half-wavelength AC transmission (HWACT) is an ultra-long distance AC transmission technology, whose electrical distance is close to half-wavelength at the system power frequency. It is very important for the construction and operation of HWACT to analyze its fault features and corresponding protection technology. In this paper, the steady-state voltage and current characteristics of the bus bar and fault point and the steady-state overvoltage distribution along the line will be analyzed when a three-phase symmetrical short-circuit fault occurs on an HWACT line. On this basis, the three-phase fault characteristics for longer transmission lines are also studied.     

Parameter identification of interconnected power system frequency after trip-out of high voltage transmission line

Accurate modeling and parameters of high voltage (HV) grid are critical for stability research of system frequency. In this paper, simulation modeling of the system frequency was conducted of an interconnected power system with HV transmission lines in China. Based on recorded tripping data of the HV transmission lines, system parameters were identified by using genetic algorithm (GA). The favorable agreement between simulation results and recorded data verifies the validity of gird models and the accuracy of system parameters. The results of this paper can provide reference for the stability research of HV power grid.     

Power conversion system for high altitude wind power generation with medium voltage AC transmission

High Altitude Wind Power (HAWP) generating system provides clean energy at low cost and high capacity factor due to reduced size of the turbine and high speed streamlined wind at high altitude. An air-borne wind turbine (AWT) at high altitude extracts kinetic energy from wind using buoyancy provided by the blimp/aerostat. The generated electrical power is then transmitted to the ground based station (without any power conditioning) using the transmission lines (tether). The power conversion system (PCS) for harnessing HAWP is proposed in this paper. The proposed PCS consists of a three-level neutral point clamped (NPC) rectifier, a three-level NPC DC–DC converter followed by a two-level inverter. Modelling, design and control of the PCS are presented and discussed. The PCS provides generation side maximum power-point tracking (MPPT) using sensorless optimal torque control technique. The DC–DC converter provides electrical isolation as well as voltage step-down functions. A modified proportional resonant (PR) control which can selectively eliminate lower order current harmonics of the grid-connected inverter is also presented. The proposed control scheme of the PCS is evaluated through simulation studies using software programs like PSIM and MATLAB. A scaled-down 1 kW laboratory prototype of the complete PCS is designed, built and tested. The experimental test results obtained validate the proposed control scheme for efficient power generation from high altitude wind and interface to the grid/load.     

变压法真空干燥工艺在油浸式电力变压器中的应用

油浸式电力变压器采用变压法真空干燥工艺，体现先进、节能、高效、环保、经济实用的优点。介绍变压法真空干燥四个阶段，技术特点。运用自动化技术进行控制加热与抽真空的关系，实现在线终点准确判断，在实践中运行中产生了显著的综合效果。     

风电系统的无功功率与电网电压稳定

论述了风电容量在占局部电网相当比例时,风电机组的无功功率调整与电网电压之间的关系,对于定速和变速风电机组的运行特性做了分析,提出了在需要做无功功率调整时风电机组应能满足的特殊要求。     

基于反馈线性化技术的直驱永磁同步风电机组低电压穿越研究

通过对直驱永磁同步风电系统的研究,提出了一种基于反馈线性化的低电压穿越控制策略。直流母线电压由发电机侧整流器来维持调节,考虑到直流母线电压和发电机转子转速的非线性关系,直流母线电压的控制采用了反馈线性化技术。网侧逆变器根据最大风能跟踪原则来控制网侧有功功率,并加入了转子速度参考值的判定环节。运用PSCAD仿真平台建立了一个2 MW的直驱永磁同步风电系统,验证了其正确性和有效性。     

The history of wireless power transmission

The history of wireless power transmission at microwave frequencies is reviewed with emphasis upon the time period starting with the post World War II efforts to use the new microwave technology developed during the war. A nationally televised demonstration of a microwave powered helicopter at the Spencer Laboratory of the Raytheon Co., in 1964 was the result of these early efforts and broadly introduced the concept of wireless power transmission to scientific and engineering communities and to the public. Subsequent development efforts centered on improving the efficiency of the interconversion of d.c. and microwave power at the ends of the system to reach a demonstrated overall d.c. to d.c. system efficiency of 54% in 1974. The response to the requirements of applications such as the Solar Power Satellite and high altitude microwave powered aircraft have changed the direction of technology development and greatly expanded the technology base. Recent and current efforts are centered on examining the use of higher frequencies than the baseline 2.45 GHz, and in reducing the system costs at 2.45 GHz.     

Stochastic reactive power market with volatility of wind power considering voltage security

While wind power generation is growing rapidly around the globe; its stochastic nature affects the system operation in many different aspects. In this paper, the impact of wind power volatility on the reactive power market is taken into account. The paper presents a novel stochastic method for optimal reactive power market clearing considering voltage security and volatile nature of the wind. The proposed optimization algorithm uses a multiobjective nonlinear programming technique to minimize market payment and simultaneously maximize voltage security margin. Considering a set of probable wind speeds, in the first stage, the proposed algorithm seeks to minimize expected system payment which is summation of reactive power payment and transmission loss cost. The object of the second stage is maximization of expected voltage security margin to increase the system loadability and security. Finally, in the last stage, a multiobjective function is presented to schedule the stochastic reactive power market using results of two previous stages. The proposed algorithm is applied to IEEE 14-bus test system. As a benchmark, Monte Carlo Simulation method is utilized to simulate the actual market of given period of time to evaluate results of the proposed algorithm, and satisfactory results are achieved.     

风电场的稳定问题

介绍了大型风电场的并网技术;指出了依据风电场的容量大小,其接入电网的电压等级也有所不同;在对风电系统的稳定性进行定位的基础上,通过对国内外包含风电场的电力系统的研究成果的对比分析,展现了不同类型的风电机组在电力系统暂态过程中的行为特性,为从事风电研究的科技工作者提供参考.     

The role of pilot projects and public acceptance in developing wireless power transmission as an enabling technology for space solar power systems

In all system concepts for delivering space solar power to terrestrial power systems, wireless power transmission (WPT) is identified as a critical link in the technology chain. To realize the full potential of WPT as an enabling technology for the development of space power systems, the technology needs to (1) be demonstrated as a commercially viable, low risk technology and (2) be shown to be acceptable to the public. If WPT's full potential is to be realized, its initial applications must be carefully chosen and demonstrated through a series of pilot projects which will develop both the technology and its public acceptance.This paper examines the role of pilot projects and how they will play an increasingly important role in the development and acceptance of WPT as an enabling technology for space solar power systems. Recognizing that public acceptance is the ultimate determinant of the commercial success or failure of a technology, the paper then explores the role of public opinion in the commercialization process of space solar power systems utilizing WPT. A framework that begins to define the process required to realize the full commercial potential of wireless power transmission is established.     

Mathematical modeling of agricultural fires beneath high voltage transmission lines

This paper presents a mathematical model for agricultural fires based on a multi-phase formulation. The model includes dehydration and pyrolysis of agricultural fuel and pyrolysis products. The model considers a homogeneous distribution of the agricultural solid fuel particles, interacting with the gas flow via source terms. These terms include: drag forces, production of water vapour and pyrolysis products, radiative and convective heat exchange. A multi-phase radiative transfer equation for absorbing-emitting medium is considered to account for the radiative heat exchange between the gas and solid phases of the fire. The main outputs of the present model are most important to study the influence of agricultural fire occurring beneath high voltage transmission lines. The agricultural fire causes a flashover due to the ambient temperature rise and soot accumulation on the insulator of these transmission lines. Numerical results of the present model are obtained for flat grassland fires to study the effects of wind velocity, solid fuel moisture content and ignition length on some selected fire outputs. These outputs include the temperature, velocity, soot volume fraction fields of the gas phase, together with fire propagation rate and flame geometry. The numerical results are compared to the available experimental work in the literature.     

Coordinated voltage control of renewable energy power plants in weak sending-end power grid

The utilization of renewable energy in sending-end power grids is increasing rapidly, which brings difficulties to voltage control. This paper proposes a coordinated voltage control strategy based on model predictive control (MPC) for the renewable energy power plants of wind and solar power connected to a weak sending-end power grid (WSPG). Wind turbine generators (WTGs), photovoltaic arrays (PVAs), and a static synchronous compensator are coordinated to maintain voltage within a feasible range during operation. This results in the full use of the reactive power capability of WTGs and PVAs. In addition, the impact of the active power outputs of WTGs and PVAs on voltage control are considered because of the high R/X ratio of a collector system. An analytical method is used for calculating sensitivity coefficients to improve computation efficiency. A renewable energy power plant with 80 WTGs and 20 PVAs connected to a WSPG is used to verify the proposed voltage control strategy. Case studies show that the coordinated voltage control strategy can achieve good voltage control performance, which improves the voltage quality of the entire power plant.     

考虑电压稳定约束的电力系统无功规划

提出一种考虑电网静态电压稳定约束的无功规划模型,采用基于预测-校正的原对偶内点算法进行求解,使系统在配置最小无功补偿容量的条件下满足安全裕度要求,并在多个IEEE标准系统和国内某个大型电网上验证了所提规划方案的合理性。结果表明,该方法具有较好的计算速度和收敛性。     

煤矿生产运输系统降压调速节能技术应用

为了降低矿井运输系统的耗电量,减少生产成本,对协庄煤矿3-1生产系统中的电机采用降压调速的节能方法,结果表明:降低电机的输入电压,进而降低电机转速的节能方法是可行的,并且这种节能方法没有增加额外的设备,保证了矿井在安全生产的前提下,达到节能降耗的目的。     

槽式太阳能聚光集热技术

详细讨论了槽式太阳能聚光集热技术的最新进展,对不同聚光集热器支撑机构进行了对比分析.结果表明,EUROTROUGH聚光器的支撑机构性能最优.此外,还对抛物面聚光镜和主要的槽式太阳能集热管技术进行了讨论分析.     

Peak power bi-directional transfer from high speed flywheel toelectrical regulated bus voltage system: a practical proposal forvehicular technology

This paper provides a design outline and implementation procedure for a secondary energy storage unit (SESU) that can be used to meet the peak energy requirements of an electric vehicle during both acceleration and regenerative braking. The life cycle of the electric vehicle's batteries can be extended considerably by supplying peak energy requirements from a secondary source. A simulation study was conducted to determine the peak power and energy requirements over the SAE recommended electric vehicle test procedure. A scaled prototype SESU was built using flywheel energy storage, and tests were performed to determine the energy transfer capabilities of a flywheel coupled high speed permanent magnet synchronous machine through the proposed system's energy storage tank. Results are presented that indicate the necessity of the energy storage tank. An evaluation of the proposed system is also included which indicates the practicality of the system when compared to conventional regenerative control techniques     

区域电压无功控制系统在地区电网中的应用

区域电压无功控制系统以电压无功的分级控制思想为指导，在调度自动化主站实现集中的、以保证负荷母线电压质量为首要目标的变电站一级控制；以220kV变电站的供电范围进行动态分区，实现区域内的二级协调控制；以基子全网实时潮流的网损灵敏度对可控设备进行在线寻优，实现准三级控制。二三级拉制中充分地考虑了电网运行的经济性要求。实践表明应用该系统是即时控制电压在合格范围、供应优质电能、降低电力服务成本度降损节能的有效措施。