Development of Superconducting AC Generator

The superconducting ac generator is expected to be the optimum choice among ac generation systems in the future because of its reduced size, weight, high efficiency, and its contribution to stability of power systems and higher generator terminal voltage. Conceptual design on a 2P-1000MVA class superconducting ac generator has been completed to clarify problems and to confirm advantages. Fundamental studies are performed on key technologies that have to be solved for realization of superconducting generators. As a summary of those fundamental studies, a scaled-down superconducting generator of 3000kVA capacity is constructed and tested. Also clarified are effects of major design parameters for commercial superconducting ac generators such as dimensions, reactances, and weight.     

Short-Circuit Current of Wind Turbines With Doubly Fed Induction Generator

The short-circuit current contribution of wind turbines has not received much attention so far. This paper considers the short-circuit behavior, especially the short-circuit current of wind turbines with a doubly fed induction generator. Mostly, these wind turbines have a crowbar to protect the power electronic converter that is connected to the rotor windings of the induction generator. First, the maximum value of the short-circuit current of a conventional induction machine is determined. The differences between a crowbar-protected doubly fed induction generator and a conventional induction generator are highlighted and approximate equations for the maximum short-circuit current of a doubly fed induction generator are determined. The values obtained in this way are compared to the values obtained from time domain simulations. The differences are less then 15%     

Ten MVA superconducting generator development: status at the end of1989

A progress report and some initial results from the experimental program in superconducting generators at the Massachusetts Institute of Technology (MIT) are provided The 10 MVA generator developed at MIT was to demonstrate a number of advanced concepts. These included a fully cold rotor, a cryogenic system with built-in reserves for rapid recooling following serious electrical transients, a two-stage damping and shielding system with a damping resistor tailored to good dynamic performance, a field winding structure which allows for full fault torque without straining the field winding conductors, a limited voltage gradient armature winding, and a monolithic armature structural system that provides both rigid support and good electrical isolation. The generator was completed in 1985, and experimentation has been carried out since then. The basic electrical parameters have been verified through low-level steady-state no-load and synchronous impedance tests, and sudden short-circuit and sudden open-circuit transient tests     

A 150 kJ/100 kW directly cooled high temperature superconducting electromagnetic energy storage system

高温超导磁储能系统（SMES）是一种功率型的储能装置,本文介绍了国内自主研发的150 kJ/100 kW直接冷却高温超导磁储能系统的总体结构和基本试验结果。高温超导磁体由Bi2223/Ag和YBCO两种超导带材绕制而成,通过直接冷却方式将储能磁体成功冷却到了17 K左右。经测试,储能磁体的直流临界电流达到180 A,临界储能量157 kJ,磁体中心场强4.7 T;该SMES能快速独立地在四象限进行有功功率和无功功率交换,响应速度小于10 ms;在电力系统动态模拟实验中,SMES有效抑制了电力系统中因发电机机端短路故障引起的功率振荡。     

500 kV超导限流器在广东电网应用选点研究

随着电力需求的不断发展,广东电网短路电流水平迅速提高。超导限流器对电力系统的正常运行无影响,一旦发生故障能够立即投入限制短路电流,达到对短路电流的抑制。以2015年作为研究水平年,以广东规划电网为研究对象,对广东500kV电网短路电流水平进行计算分析。综合考虑超导限流器安装对短路电流的抑制效果、对电网发展的适应性及对电网运行的影响等方面来进行其在广东电网应用选点方案的研究,推荐西江站、东纵站及深圳站考虑作为加装超导限流器的站点,有力降低广东电网短路电流水平,促进广东电网发展。     

Electrical issues associated with sea-water immersed windings in electrical generators for wave- and tidal current-driven power generation

For the majority of proposed wave- and tidal current-driven power generation applications, the electrical generators are submerged in sea water, frequently at many metres of depth. The environment places significant stress on the rotating or translating seals between the driven shaft and the electrical generator leading to reduced reliability and lifetime. A potential solution is to eliminate the seal, thereby flooding the generator and allowing sea water to circulate around the shaft, windings and rotor of the machine. The impact of immersing the windings of the machine in sea water is assessed here. Specifically, the impact that the insulation has on the leakage capacitance as well as the consequent impact the leakage capacitance has on current and voltage oscillations in the switching converter used to excite the winding is assessed. Thermal tests are conducted to assess the impact of the insulation on the thermal conductance of the coil?insulation system. Experimental evidence is provided.     

A sophisticated maximum capacity analysis for large turbine generators considering limitation of temperature

In this paper, the authors propose a sophisticated analysis method to determine possible maximum generator capacity and to evaluate the generator's potential ability. The method surveys generator design parameters on a large scale efficiently and objectively. The possible maximum generator capacity acquired by the proposed method satisfies the specifications of short-circuit ratio, power factor, and temperature limitations of armature and field windings. Armature voltage, armature current, and field current are adjusted to satisfy the above specifications simultaneously. An example adopting the proposed method is shown which clarifies the method's effectiveness in the research and design phase. The specific results obtained demonstrate the sensitivities of the calculated possible maximum generator capacity and the calculated loss for various development factors.     

Short-circuit tests on a high-voltage, cable-wound hydropower generator

Data from measurements on the first Powerformer generator installed in Porjus, Sweden, will be presented. The generator has a rating of 45 kV and 11 MVA. In total, the machine has been running more than 13700 h (October 2001) and has been exposed to a number of different tests including short-circuit tests on the terminal at 100% magnetization. Experience and some results from these short-circuit tests will be presented. Also, the response on the auxiliary winding during a short circuit on the main winding will be shown.     

The disk generator,its status and its potential

The MHD disk generator has been used as an experimental tool to study plasma properties and to explore new diagnostic techniques, since it provides a near-ideal geometry for plasma studies due to its electrodeless configuration combined with near-perfect insulating walls. Both experimental and theoretical studies have also determined the conditions for favorable performance of the disk, often with inlet swirl, as a configuration for electrical power generation in both open and closed cycle applications. This paper describes the state-of-the-art of the disk geometry for power generation, and it also reviews recent system studies which have integrated the disk generator in electrical power plants using coal as a fuel. These studies indicate that the disk system can achieve overall efficiencies comparable to linear generator systems, but they also show that the disk configuration might provide significant reliability and require lower capital investments. These cost advantages are derived from the simplicity of the superconducting magnet and power management systems.     

Controlled power transfer from wind driven reluctance generator

The paper describes the dynamic performance of a wind-driven reluctance generator connected to an electric power network of large capacity. A controller that makes possible the regular flow of power to the network has been considered. Controller parameters that successfully suppress unwanted mechanical and electrical stresses and overshoots due to wind gusts, have been estimated. The performance of the controller has also been examined for short-circuit faults at the terminals of the generators     

Application analysis of a superconducting fault current limiter-magnetic energy storage system for the wind farm

风力发电所面临的两大重要问题是低电压穿越能力弱和功率输出不稳定。为了同时解决这两个问题,我们提出了超导限流-储能系统,并进行了单机系统的仿真研究,证实了该方案的有效性。然而对于风电场的应用,目前尚无研究。本文将超导限流-储能系统的应用扩展到风电场,分析了其提高低电压穿越能力和稳定有功功率输出的机理,并进行了仿真研究。从仿真结果来看,超导限流-储能系统能够同时提高风电场所有风机的低电压穿越能力,并能有效地平滑整个风电场的有功输出功率。考虑不同风机的互补效应,将该系统应用于风力发电场与直接应用于单台风机相比,其储能量和功率输出的要求可以大大降低,从而可以有效地减少系统总成本,因而具有更好的应用前景。     

Experimental method for synthesis of generalized thermal circuit ofpolyphase induction motors

A new method for determining the equivalent parameters of a generalized thermal model of induction motors (IM) based on the no-load testing of IM is presented. The representation of the full thermal network of IM is reduced to a system of only three simultaneous equations. By solving these equations three equivalent thermal parameters of the generalized thermal model are obtained. The calculation is based on accurate measurements of the temperature rise in stator windings and the power absorbed by the tested motor. The thermal tests are done in the no-load running of IM (one test is like an open-circuit test and the other two are like short-circuit tests). Hence these methods of testing may be carried out without expensive equipment and their power consumption does not exceed the losses, which occur under full load conditions. With the help of this thermal model the final temperature rise at the full load run according to rated losses, can be easily estimated. Three totally enclosed IM were tested by these methods and the difference in the predicted and measured temperature rise of the stator winding was within 2-3°C     

Multivariable adaptive control for a thermal generator

A digital control system using the optimal control has been developed for a thermal power generator. In order to increase the generator control performance for improving the power system stability, this system supplies the excitation system directly with control signals and provides the governor system with control signals and supplemental control signals for a conventional governor. The system utilizes adaptive control for changes in generator nonlinear characteristics, as well as in power system characteristics. The principles and application of this system are described and results of simulation tests using a 1000 MVA thermal power plant model on a high-reliability AC/DC electric power system simulator are presented. The results verify the performance of this system, as well as the applicability of the system to actual plants     

Damper windings phenomena of synchronous machines during systemoscillations

The performances of the damper windings of a synchronous machine (generator) under the oscillatory conditions of the power system to which it is connected, are investigated both experimentally and analytically in this paper. Air-gap fluxes and induced voltages and currents of the damper windings under the oscillatory system conditions, when the machine is equipped both with and without damper windings, are measured and analyzed. Fourier analyses are used to examine the harmonic components appearing in the air-gap flux density distributions and the damper induced voltages and currents to clarify the phenomena caused by the damper as well as the effect of the damper upon power system performances     

Design installation and commissioning of the Los Alamos NationalLaboratory pulsed power generator

A 1430 MVA synchronous generator from a canceled nuclear power plant has been installed and commissioned at Los Alamos National Laboratory to provide pulsed power and energy for large physics experiments. The authors describe special studies, tests, and design modifications to enable a high-power, steady-state machine to operate as a pulsed, variable-speed generator. The generator rotor and stator core cooling have been changed from hydrogen to air to facilitate the operation. An all-solid-state drive system accelerates the generator rotor from standstill to the maximum operating speed of 2800 rpm and from 1260 rpm to 1800 rpm between load pulses. The excitation system has been modified to provide both the motor and generator mode of operation. The generator is mounted on a spring foundation to minimize the transmission of shaft vibrations into the subsoil. The springs also dampen shocks stemming from the pulsed loads     

A grid-interactive photovoltaic uninterruptible power supply systemusing battery storage and a back up diesel generator

This paper presents a practical implementation of a grid interactive photovoltaic uninterruptible power supply (UPS) system using battery storage and a back up diesel generator. The system incorporates 2.5 kWp of photovoltaic arrays, a 10 kVA power conditioning unit capable of operating in both inverting and charging modes, and a 300-Ah battery bank. Two such systems were installed in two Indian cities. The project was implemented using soft loans available in India through a World Bank Loan for photovoltaic market development. The system has been working satisfactorily since May 1997 and has demonstrated the capability of the system to provide uninterrupted power, demand side management function and load voltage stabilization in a grid which experiences frequent blackouts and under/over voltage problems. Some results from the field installation are also included in this paper     

A pulse-amplitude-synthesis-and-control (PASC)consolidation/inversion system for Faraday connected MHD generators

The problem of consolidating and inverting a number of DC sources is common in interconnecting arrays of batteries, fuel cells, solar cells, multi-electrode pair magnetohydrodynamic (MHD) generators, etc. This paper describes a general technique for performing such power processing when applied to the specific example of consolidation followed by three phase inversion, of a number of DC sources produced by a Faraday connected MHD generator. The method employs banks of pulse transformers, one bank per phase, in which the secondaries of each transformer have been connected in series and two opposite polarity primaries are pulsed from the DC sources. The sequence in which the primaries are pulsed determines the shape of the resulting AC waveform. The process, or method, is called PASC (pulse amplitude-synthesis-and-control), and utilizes a switching array to connect/disconnect one or more DC sources in an overlapped fashion under computer actuation along with error output-signal feedback, to generate the control necessary to match the desired waveform as specified in the computer. Although the principle benefit of this system is consolidation of diverse and isolated DC sources, it is shown that quantized sinusoids can be synthesized with low harmonic content precluding the need for expensive and inefficient filtering such as is required by conventional static inverters. A prototype single phase, 24 kVA, eight transformer system has been built and extensively tested. This system is described and representative experimental results are shown     

A Multivariable Optimal Control System for a Generator

A new digital generator control system has been developed, which coordinates excitation and governing systems of a generator by using multivariable optimal control scheme on the basis of modern control theory. Control performance of the developed system was investigated with computer simulations and tested at a 200KVA pilot power plant with 3KV transmission lines. This paper first outlines the control system, next describes the control schemes including process models, optimal control algorithms, control sequence, and state estimation schemes, and finally shows its control performance obtained from the pilot plant tests and the computer simulations.     

多对极发电机励磁绕组匝间短路故障在线定位理论研究

大型水轮发电机和抽水蓄能发电电动机均为多对极,现场迫切希望实现故障磁极的在线定位.本文基于一台3对极、12kW的发电机动模样机研究在线定位的理论基础.首先,采用场路结合法对该样机在联网工况下的励磁绕组匝间短路故障进行了计算,并与实验结果进行了对比和分析,验证了计算模型的正确性.然后,利用故障数学模型对该样机一极短路故障...     

Design and Testing of a 1000-hp High-Temperature Superconducting Motor

A synchronous motor with a high-temperature superconducting field winding has been successfully constructed and tested. Designed to produce an output power of 1000 hp, this motor was operated successfully at this power rating and achieved an output power of 1600 hp during subsequent testing. This paper provides an overview of the design of the motor and discusses the results of a series of tests which were performed on the motor.