Potential Industrial Applications of Magnetohydrodynamics

Magnetohydrodynamic power generation has been presented as limited in application to large generating stations but offering the promise of reduced power cost to be achieved through heat rate improvement. The potential for industrial application will be broadened if generators can be made attractive in smaller ratings, if generating cost can be reduced, and if the generator can be made lighter and more compact. The scaling considerations which make large output more favorable will be reviewed and the possibility of devising attractive MHD generators in smaller ratings will be explored. Improved heat rate is achieved by the combination of an open-cycle regenerative MHD generator with a waste heat steam cycle; however, cost studies of such combined cycles have shown that high capital costs may prevent the expected improvement in the cost of power generated. This cost is decreased by extracting a larger portion of available heat in the MHD converter relative to that extracted in the steam cycle. The effect on power cost of increasing generator inlet temperature without a corresponding increase in exit temperature will be examined. MHD generator size affects power cost both through wall heat loss and as a consequence of magnet capital cost. The effect of magnetic field strength upon generator power density and cost will be discussed and the potential benefit of the superconducting electromagnet will be established.     

Gyrator Realization Based on a Capacitive Switched Cell

Efficient power gyrator realization by means of a controlled switch cell is presented. It is shown that a switching cell may be controlled so as to acquire low-frequency gyrative characteristics (on average). A realization suitable for operation with current sources is presented, that employs a switched capacitor. Due to the capacitive input, a gyrator of this nature is suitable for operation with current sources. The main applications of such gyrators are expected in superconductive magnetic energy storage systems and current-fed converters, due to the stiff-current characteristic imposed by a magnetic storage element. Other possible applications include sources with softer i-v characteristics, such as photovoltaic generators and sources of significant output inductance     

A MEMS-based piezoelectric power generator array for vibration energy harvesting

Piezoelectric power generator made by microelectromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed MEMS power generators are featured with fixed/narrow operation frequency and power output in microwatt level, whereas, the frequency of ambient vibration is floating in some range, and power output is insufficient. In this paper, a power generator array based on thick-film piezoelectric cantilevers is investigated to improve frequency flexibility and power output. Piezoelectric cantilevers array has been designed and fabricated. The cantilevers array can be tuned to the frequency and expanded the excited frequency bandwidth in ambient low frequency vibration. Serial connection among cantilevers of the array is investigated. The prototype generator has a measured performance of 3.98 μW effective electrical power and 3.93 DC output voltage to resistance load. This device is promising to support networks of ultra-low-power, peer-to-peer, wireless nodes.     

Experimental study of diagonal conducting wall generators using solid propellants

The work reported here is the result of using a special solid fuel developed as a working fluid for MHD generators by Hercules Inc. Conductivity measurements of the combustion products were made using the electrodes of the Hall channel as floating potential probes. The experimentally determined values of the average conductivity for this type of propellant were found to be in the range between 40 and 50 mho/m. Generator experiments were performed with two different types of channels operating as a Hall generator and as a 45° diagonal conducting wall generator. The generator power output was found to be 3 to 4 times higher than that achieved by even higher flow rates using conventional RP1 and gaseous oxygen for the same generator channel and magnetic field conditions. However, the power increase was insignificant for the Hall generator. The generators operated with relatively little effect observed when coatings of aluminum oxide and other chemicals from the fuel covered the interior of the channel.     

Thyristor-based current-fed drive with direct power control for permanent magnet-assisted synchronous reluctance generator

This paper proposes a robust and simple direct power control (DPC) of a thyristor-based current-fed drive for generator applications. A current-fed drive and permanent magnet-assisted synchronous reluctance generator (PMa-SynRG) are investigated to deliver 3 kW power using a combustion engine. The current-fed drive utilises a thyristor-based three-phase rectifier to convert generator power to DC-link power and a single-phase current-fed inverter to supply a single-phase inductive load. In addition, a new control algorithm is developed based on DPC for the current-fed drive. The DC-link voltage-based DPC is proposed in order to directly control the output power. The goal of the DPC is to maintain the DC-link voltage at the required output power operating point. The DPC has advantages such as a simple algorithm for constant speed operation. Another feature of the developed current-fed drive is its inherent capability to provide generating action by making the PMa-SynRG operates as a generator, rectifying the phase voltages by means of the three-phase rectifier and feeding the power into the load. These features make the current-fed drive a good candidate for driving any type of synchronous generators including the proposed PMa-SynRG.     

基于半导体断路开关的脉冲功率源及其应用

半导体断路开关效应的发现促进了能连续重复频率运行的半导体断路开关和基于这种开关的高平均脉冲功率源的发展和应用,与其它应用于脉冲功率源的传统器件相比,基于SOS的脉冲功率源更简单、可靠,其脉冲重复频率可达到kHz。介绍了SOS和基于SOS的脉冲功率源的基本工作原理和特性,并总结了基于SOS的脉冲功率源最新的研究进展和应用。     

A novel design method for discrete time chaos based true random number generators

Discrete time chaos based true random number generators are lightweight cryptographic primitives that offer scalable performance for the emerging low power mobile applications. In this work, a novel design method for discrete time chaos based true random number generators is developed using skew tent map as a case study. Optimum parameter values yielding maximum randomness are calculated using a mathematical model of true random number generator. A practical information measure is used to determine the maximum allowable parameter variation limits. Appropriate mapping between dynamic system and circuit parameters is established and a current mode skew tent map circuit is designed to validate proposed method.     

Compact solid-State switched pulsed power and its applications

Power semiconductor devices, such as insulated-gate bipolar transistors, metal-oxide-semiconductor field-effect transistors, and static-induction thyristors, are used in different kinds of pulsed power generators developed for different applications. In addition, the semiconductor opening switch is found to have very effective applications in pulsed power generation by inductive energy storage. Semiconductor switches have greatly extended the scales of pulsed power parameters, especially in repetition rate and lifetime. They have also enabled new areas of pulsed power applications, such as accelerators, flue-gas treatment, and gas lasers.     

组合开关高功率脉冲调制电路的研究

采用环形电极结构的气体火花开关和电爆炸丝断路开关,研制了高功率脉冲调制电路。该电路通过压缩陡化爆炸磁频率发生器的输出而产生上升沿为纳秒级的宽频脉冲信号。结合球形和平面形结构电极,对环形电极脉冲陡化实验进行对比分析;根据电爆炸丝电阻率与比作用量的关系,在电路仿真软件Pspice中建立模型,并对电爆炸丝快速断路特性的数值仿真以及相关的实验研究;最后,进行了脉冲调制电路的实验,结果表明:在注入能量为35kV时,获得了上升沿为1.68ns、峰值为197kV的脉冲电压信号,压缩能量达到5倍以上,为下一步脉冲调制电路与爆磁压缩发生器的联合调试提供了理论依据和实验支持。     

Application of Radioactive Isotopes for Beta-Voltaic Generators

The features of using radioactive isotopes when creating off-line power supplies are considered. The analysis of the substances used in radioisotope thermoelectric generators (RTGs) is carried out. The prospects for manufacturing beta-voltaic generators are justified and they are compared with other electric power sources. The mechanism of β-decay and its place among other types of nuclear transformations is considered. The basic requirements for radiation safety and the used materials of the frame and converter are formulated. Some designs of radioisotope beta-voltaic sources proposed earlier are considered. A list of isotopes that can be used as a power source in a beta-voltaic generator is presented. The methods for obtaining the radioactive materials demonstrating β-decay and their basic properties and natural isotopes are considered. It is concluded that the choice of nickel-63 isotope is preferable for use in beta-voltaic generators due to the optimal combination of its half lifetime, average particle energy, and radiation intensity.     

Modeling of electromagnetic power output in a vibration-induced micro-generator with a silicon-based helical micro-spring

This paper develops an electromagnetic power output model in a vibration-induced micro-generator with a silicon helical micro-spring to predict the electricity output. The generator consists of a movable ferro-platinum permanent magnet membrane on the micro-spring, a winding copper induction coil and two glass spacers. This model considers the coupling issues of mechanical kinematics and electromagnetism that convert mechanical energy to electric energy through vibration. Analytical formulas are developed to predict analyze the values in the spring constant of the helical micro-spring, a three-dimensional magnetic field of electromagnetic induction and the parasitical damping coefficient. Good agreement between the analysis and experiment: 82.6% precision for power output, 6.2% difference for current output and 9.6% deviation for voltage output are demonstrated at 60 Hz vibration frequency with a 0.03 mm vibration amplitude. From a series of analytical results, it is known that a 4.2 times power output can be achieved by controlling the oscillator with an appropriate vibration amplitude and the best-designed load resistance.     

High-Temperature Superconducting Homopolar Inductor Alternator for Marine Applications

This paper describes a high power density high-temperature superconducting (HTS) electric machine topology that is scalable for marine propulsion and power generation. The design, currently being pursued for airborne applications, is based on homopolar inductor alternator (HIA) technology, which is new within HTS applications. The basic machine design configuration of the HTS HIA is based on a stationary HTS field excitation coil, a solid rotor, and an advanced but conventional stator comprising liquid-cooled air-gap armature winding and an advanced iron core. High power density is obtained by the enhanced magneto-motive force capability of the HTS coil, the increased airgap flux density and armature current loading, and the high tip velocity of the rotor. Preliminary scaled up designs look attractive for three marine applications: propulsion drive, primary ship power generation, and power generation modules. The generators are driven directly by the turbines without the additional complexity of a clutch and gear system. A conceptual design study of a 36-MW 3600-r/min generator, a 4-MW 7000-r/min auxiliary generator, and a 36-MW 120-r/min and 4-MW 132-r/min propulsion motor are summarized.     

A Novel Pseudorandom Noise and Band Jammer Generator Using a Composite Sinusoidal Function

Communication applications are increasingly relying on spread-spectrum techniques requiring the use of different types of pseudorandom noise generators (PRNGs). Such generators typically produce periodic deterministic signals, with key attributes of PRNGs being: signals produced have long periods, a large number of weakly correlated signals is produced with compatible spectral properties, most of the signal power of generated signals is contained in the desired frequency band, and arbitrary band selectivity of produced signals. Random generators can also be used for band jamming, with key attributes for band jamming being: most of the signal power is contained in the desired frequency band, arbitrary band selectivity, and a considerably flat power spectral density within the selected band. In this paper, a novel PRNG approach is proposed that can be used in several applications, including spread-spectrum techniques, as well as in band jamming. The signals produced by the proposed generator are based on a linear combination of continuous-time composite sinusoidal functions. Numerical examples are included in order to illustrate the performance of the proposed generator.      

100kJ级多路强电脉冲发生装置的同步精度技术研究

本文介绍了＂多路强电（磁）脉冲发生装置＂同步精度研究采用的每路输出＂储能电容＋同轴脉冲大电流火花开关放电＂型高压脉冲形成电路。用同轴电缆作为传输线将工作部件连接起来,以脉冲气体激光器作为终端负载（或其他负载,如磁脉冲线圈、电水锤等）组成多路相互隔离的强电脉冲充放电路,设计采用＂多路高压纳秒脉冲发生器装置＂进行同步精度触发,使高功率气体激光器的放电系统同时获得多路同步输出的高强电脉冲能量进行激励放电。同步精度装置的实验研究结果表明,多路同步导通强电脉冲能量已超出100kJ级,多路触发脉冲同步精度〈10ns,可为脉冲气体激光器提供更加超强激励触发能量获得高功率激光。     

On low-frequency electric power generation with PZT ceramics

Piezoelectric materials have long been used as sensors and actuators, however their use as electrical generators is less established. A piezoelectric power generator has great potential for some remote applications such as in vivo sensors, embedded MEMS devices, and distributed networking. Such materials are capable of converting mechanical energy into electrical energy, but developing piezoelectric generators is challenging because of their poor source characteristics (high voltage, low current, high impedance) and relatively low power output. In the past these challenges have limited the development and application of piezoelectric generators, but the recent advent of extremely low power electrical and mechanical devices (e.g., MEMS) make such generators attractive. This paper presents a theoretical analysis of piezoelectric power generation that is verified with simulation and experimental results. Several important considerations in designing such generators are explored, including parameter identification, load matching, form factors, efficiency, longevity, energy conversion and energy storage. Finally, an application of this analysis is presented where electrical energy is generated inside a prototype Total Knee Replacement (TKR) implant.     

脉冲气体激光器用固态高压开关的研制

实验研制了基于磁脉冲压缩系统的脉冲气体激光器用固态高压开关,实验中通过调节复位电流大小,负载电阻大小等相关参数实现了磁压缩开关输出效率达到最大值。经两级磁开关压缩后脉宽约压缩为原来的5%。压缩后脉冲上升时间约为180 ns,幅值约为16 kV。其中第一级磁压缩效率为89.2%,第二级磁压缩效率达到97.7%,总的压缩效率达到87.2%。接激光器后测得输出激光脉冲能量约为20 mJ,输出激光脉冲半高宽约为85 ns。     

Flexible control of small wind turbines with grid failure detection operating in stand-alone and grid-connected mode

This paper presents the development and test of a flexible control strategy for an 11-kW wind turbine with a back-to-back power converter capable of working in both stand-alone and grid-connection mode. The stand-alone control is featured with a complex output voltage controller capable of handling nonlinear load and excess or deficit of generated power. Grid-connection mode with current control is also enabled for the case of isolated local grid involving other dispersed power generators such as other wind turbines or diesel generators. A novel automatic mode switch method based on a phase-locked loop controller is developed in order to detect the grid failure or recovery and switch the operation mode accordingly. A flexible digital signal processor (DSP) system that allows user-friendly code development and online tuning is used to implement and test the different control strategies. The back-to-back power conversion configuration is chosen where the generator converter uses a built-in standard flux vector control to control the speed of the turbine shaft while the grid-side converter uses a standard pulse-width modulation active rectifier control strategy implemented in a DSP controller. The design of the longitudinal conversion loss filter and of the involved PI-controllers are described in detail. Test results show the proposed methods works properly.     

A New Interconnecting Method for Wind Turbine/Generators in a Wind Farm and Basic Performances of the Integrated System

A new interconnecting method for a cluster of wind turbine/generators is proposed, and some examples of the basic characteristics of the integrated system are shown. This method can be achieved with a wind turbine generating system using a shaft generator system. A group of wind turbine/generators can be interconnected easily with the proposed method, and high reliability and electric output power with high quality are also expected. Moreover, since this method enables transmission of the generated power through a long-distance dc transmission line, the optimum site for wind turbines can be selected so as to acquire the maximum wind energy.      

Pulsed 0.75kW output single-ended GaN-FET amplifier for L/S band applications

A pulsed 0.75 kW output GaN-FET amplifier for L/S band high power applications has been successfully developed. A single-ended configuration is adopted to make the amplifier compact and simple. The amplifier delivers a saturated output power of 0.75 kW under pulsed RF operation at 2.14 GHz, which is believed to be the highest output power reported in an L/S band single-packaged device     

A Comb-Filtered Noise Generator for Use in Auditory Neurophysiological and Psychophysical Experiments

A digital CMOS comb-filtered noise generator has been developed for use as a stimulus in auditory physiological and psycho-physical experiments. It incorporates two identical, 34-bit shift register pseudo-random noise generators whose outputs are summed and low-pass filtered. By introducing a delay between the generators, a noise power spectrum results which is co-sinusoidal on a linear frequency scale (i.e., "comb-filtered"). The generator may be operated either manually or automatically with a range of delays of 1 Ps or greater, selectable in 1 ps increments. The polarity of one of the shift registers may be changed to produce an inverted output spectrum. The peak-to-valley ratio of the spectrum is adjustable in discrete steps over the range from 0 to 35 dB. The output noise is low-pass riltered at 50 kHz, and has Gaussian amplitude characteristics to 3 a.