电气工程及其自动化电压波动论文中英文资料外文翻译文献

Section 1 Introduction 第一节介绍The modern society depends on the electricity supply more heavily than ever before.现代社会比以往任何时候对电力供应的依赖更多。

It can not be imagined what the world should be if the electricity supply were interrupted all over the world. 如果中断了世界各地的电力供应，无法想像世界会变成什么样子Electric power systems (or electric energy systems), providing electricity to the modern society, have become indispensable components of the industrial world. 电力系统（或电力能源系统），提供电力到现代社会，已成为产业界的不可缺少的组成部分。

The first complete electric power system (comprising a generator, cable, fuse, meter, and loads) was built by Thomas Edison –the historic Pearl Street Station in New York City which began operation in September 1882. 托马斯爱迪生建立了世界上第一个完整的电力系统（包括发电机，电缆，熔断器，计量，并加载）它就是位于纽约市具有历史意义的珍珠街的发电厂始于1882年9月运作。

This was a DC system consisting of a steam-engine-driven DC generator supplying power to 59 customers within an area roughly 1.5 km in radius. The load, which consisted entirely of incandescent lamps, was supplied at 110 V through an underground cable system. 这是一个直流系统，由一个蒸汽发动机驱动的直流发电机其供电面积约1.5公里至59范围内的客户。

本科毕业设计外文文献及译文文献题目：Direct Torque Control of Induction MotorsUtilizing Three-Level Voltage Source Inverters 文献作者： Xavier del Toro Garcia, Antoni Arias, Marcel G.Jayne and Phil A. Witting文献来源： IEEE Trans. Ind. Electron, vol. 51，No. 4，pp.744–757发表日期：2004年8月班级：姓名：学号：指导教师：翻译日期：英文原文：Direct Torque Control of Induction Motors Utilizing Three-Level Voltage Source Inverters Xavier del Toro Garcia, Antoni Arias, Marcel G. Jayne,and Phil A. WittingAbstract—A new control strategy for induction motors based on direct torque control is presented which employs a three-level inverter instead of the standard two-level inverter. The controller is designed to achieve a torque ripple reduction by taking advantage of the increase in the number of inverter states available in a three-level inverter. The harmonic distortion in the stator currents and the switching frequency of the semi-conductor devices are also reduced in the new control system presented.Index Terms—Induction motor drives, three-level converter, torque control.I. INTRODUCTIONThe standard voltage source inverter (VSI) traditionally used in electrical drive systems is the two-level VSI, which unfortunately has a number of inherent limitations. For example, the maximum voltage that can be supported by the semiconductor switching devices in the VSI limits the maximum value of dc-link voltage. Furthermore, the output voltages and currents from the VSI can contain high harmonic distortion.The output voltage waveforms can also contain large values of dV/dt, which contribute to the degradation of the machine windings insulation and bearings, and also produce considerable electromag-netic interference during operation. New multilevel VSI topologies,however, can considerably reduce many of these limitations [1].The most commonly used multilevel topology is the three-level neutral point clamped (NPC) VSI[2]. This type of VSI has advantages over the standard two-level VSI, such as a greater number of levels in the output voltage waveforms, less harmonic distortion, and lower switching frequencies.Direct torque control (DTC) has emerged to become a possible alternative to the well-known vector control strategies for induction motor control systems [3], [4]. Although considerable research has been made into the two-level topologies associated with this method of control, the amount of research carried out to date into DTC systems employing multilevel topologies is still rather limited. The major advantage of the three-level VSI topology when applied to DTC is the increase in the number of voltage vectors available. This means the number of possibilities in the vector selection process is greatly increased and leads to a more accurate control system, which can result in a reduction of the torque and flux ripples. This is of course achieved at the expense of an increase in the complexity of the vector selection process. Although several authors have recently proposed the implementation of DTC utilizing this higher-level topology, their approaches are based on the use of more complex vector selection tables combined with modulation techniques based on analytical methods which have machine parameter dependency[5] [6]. A different approach is a selection table based on the concept of virtual vectors [7]. These new methods considerably increasethe complexity of the control strategy when compared to the classical DTC system[3], and they cannot be extended to different multilevel topologies with a higher number of levels because of the table selection method adopted.Fig. 1. Schematic diagram of the new controller.This paper describes a controller based on DTC that can be applied to different multilevel VSI topologies. It avoids the use of hysteresis comparators and look-up tables, and it does not require the knowledge of the motor model in the control system except for the inherent estimator as in the classical DTC system.II. NEW CONTROLLERThe general structure of the new controller is shown in Fig. 1. This novel controller generates a reference stator voltage vector (u∗s) in α–βcoordinates (usα,usβ) according to the DTC basic principle, rather thanusing the VSI state look-up table as used in classical DTC. This approach adopted is close to the DTC with space vector modulation scheme with closed-loop flux and torque control, and stator flux oriented control [4]. More recently, other similar methods based on the predictive torque control concept have appeared [8] [9].The inputs to the controller are the stator flux error (eψs),the torque error (eΓe) and, additionally, the stator flux angular speed (ωB),which is obtained to incorporate the back electromotive force (BEMF) term to improve the torque response at different operating points. The reference voltage vector calculated by the controller can be synthesized using different techniques with different degrees of complexity, such as choosing the nearest vector available or using modulation techniques [9]–[11]. This controller can be applied to any topology because the type of VSI only affects the way the reference voltage vector has to be synthesized.The controller is based on the principle that the desired decoupled control of the stator flux modulus and torque is achieved by the controller acting on the respective radial and tangential components of the stator flux vector (ψB). The variation of the stator flux vector is approximately proportional to the voltage vector applied to the motor. Therefore, when calculating the reference voltage vector (in x–y coordinates fixed to the stator flux vector), the tangential component (u∗sy) will depend on the torque error (eΓe), whereas the radial component (u∗sx) will depend on the stator flux error (eψB). As can be seen in Fig. 1, two closed-loop proportional controllers are employed to generate the components of the reference voltage vector. Kψs and KΓe are the proportional gains of these controllers and have been tuned experimentally to achieve a minimum torque and flux ripple. Their initial values can be set to approximately theratio between nominal stator voltage and nominal stator flux modulus for Kψs, and the ratio between nominal stator voltage and nominal stator fluxFig. 2. Torque response characteristics for classical DTC with a two-level VSI. Operating point: Γ=7.4 Nm. ωm = 200 r/min.modulus for Kψs, and the ratio between nominal stator voltage and nominal torque for KΓe.It can be seen in Fig. 1 that a feedforward action that compensates the BEMF term is added to the output of the torque controller to calculate the tangential component of the reference voltage vector. The BEMF term is obtained by multiplying the nominal stator flux modulus (ψsn) and the stator flux angular speed (ωs), which is previously filtered by means of a low-pass filter.The reference vector in x–y coordinates is then transformed to α–β fixed coordinates. The novel controller developed synthesizes the reference voltage by choosing the nearest VSI vector to the reference voltage vector. The nearest vector is found by means of calculating the minimum distance of the voltage vectors that can be delivered by the VSIto the reference voltage vector. This calculation involves evaluating the modulus of the difference between vectors. The complexity of the system presented is increased when compared to classical DTC due to the use of proportional controllers instead of hysteresis comparators, the x–y to α–β coordinate transformation and the method to find the nearest vector. Finally, it should be noted that the balance of the neutral point voltage is one of the main issues associated with the control of the three-level NPC VSI [11]. In the novel controller the balance is achieved by selecting the appropriate configuration among the redundant possibilities that exist for some of the vectors delivered by the VSI.III. EXPERIMENTAL RESULTSThe practical implementation of the new controller is based on a dSpace DS1103 board that performs the control tasks. This board contains a PowerPC and a DSP. A three-level NPC VSI utilizing IGBT devices is used to supply a 380/220-V four-pole 1.1-kW cage-rotor induction motor. The dc-link voltage employed is 200 V. Figs. 2 and3 show the steady-state torque responses at 200 r/min and nominal torque conditions (7.4 Nm) for the classical DTC strategy with a two-level VSI and the new control system employing a three-level VSI described in this paper, respectively. The sample time used was 100 µs in both systems.To assess the performance of both systems, the torque standard deviation (σΓe) is calculated for the torque ripple. Additionally, the flux standard deviation (σψs), the total harmonic distortion (THD) of the stator current THD_iS, and the mean switching frequency in the semiconductor devices (FSw) are calculated for both systems. From the experimentalresults shown in Figs. 2 and 3, it is apparent that the torque ripple for the new system utilizing a three-level VSI is considerably reduced. The resultFig. 3. Torque response characteristics for the new controller with a three-level VSI. Operating point: Γ=7.4 Nm. ωm = 200 r/min.of the VSI switches in the proposed system are both reduced by more than 50%. The switching frequency is reduced due to the utilization of a three-level VSI. In this type of VSI, some transitions between the three possible states of a leg do not involve the commutation of all the switches.IV. CONCLUSIONA new controller based on the DTC principle is presented, and it is shown that the controller can be easily implemented in a three-level VSI drive system. The new controller does not involve the use of any motor model parameters, as in classical DTC, and therefore, the control systemis more robust compared to other methods that incorporate motor parameters. The experimental results obtained for the new DTC scheme employing a three-level VSI illustrate a considerable reduction in torque ripple, flux ripple, harmonic distortion in the stato currents,and switching frequency when compared to existing classic DTCsystems utilizing the two-level VSI.REFERENCES[1] J. Rodriguez, J. Lai, and F. Z. Peng, “Multilevel inverters: A survey of topologies, controls, and applications,” IEEE Trans. Ind. Electron.,vol. 49, no. 4, pp. 724–738, Aug. 2002.[2] A. Nabae, I. Takahashi, and H. Akagi, “A new neutral-point-clamped PWM inv erter,” IEEE Trans. Ind. Appl., vol. IA-17, no. 5, pp. 518–523,Sep./Oct. 1981.[3] I. Takahashi and T. Noguchi, “A new quick-response and high-efficiency control strategy of an induction motor,” IEEE Trans. Ind. Appl.,vol. IA-22, no. 5, pp. 820–827, Sep./Oct. 1986.[4] G. Buja and M. P. Kazmierkowski, “Direct torque control of PWM inverter-fed AC motors—A survey,” IEEE Trans. Ind. Electron., vol. 51,no. 4, pp. 744–757, Aug. 2004.[5] K.-B. Lee, J.-H. Song, I. Choy, and J.-Y. Yoo, “Torque ripple reduction in DTC of induction motor driven by three-level inverter with low switching frequency,” IEEE Trans. Power Electron., vol. 17, no. 2, pp. 255–264,Mar. 2002.[6] G. Brando and R. Rizzo, “An optimized algorithm for torque oscillation reduction in DTC-induction motor drives using 3-level NPC inverter,” in Proc. IEEE ISIE, Ajaccio, France, Jun. 2004, pp. 1215–1220.[7] Z. Tan, Y. Li, and M. Li, “A direct torque control of induction motor based on three-level NPC inverter,” in Proc. IEEE PESC, Vancouver, BC, Canada, Jun. 2001, pp. 1435–1439.[8] P. Correa, M. Pacas, and J. Rodríguez, “Predictive torque control for inverter-fed induction machines,” IEEE Trans. Ind. Electron., vol. 54,no. 2, pp. 1073–1079, Apr. 2007.[9] M. Nemec, D. Nedeljkovic, and V. Ambroic, “Predictive torque control of induction machines using immediate flux control,” IEEE Trans. Ind. Electron., vol. 54, no. 4, pp. 2009–2017, Aug. 2007.[10] A. K. Gupta and A. M. Khambadkone, “A space vector PWM scheme for multilevel inverters based on two-l evel space vector PWM,” IEEE Trans. Ind. Electron., vol. 53, no. 5, pp. 1631–1639, Oct. 2006.[11] J. Pou et al., “Fast-processing modulation strategy for the neutral-point-clamped converter with total elimination of low-frequency voltage oscillations in t he neutral point,” IEEE Trans. Ind. Electron., vol. 54, no. 4, pp. 2288–2294, Aug. 2007.中文译文：基于三电平电压型逆变器的异步电机的直接转矩控制摘要：一种基于直接转矩控制的电动机的新型控制方式，其采用了三电平逆变器，而非标准的两个电平逆变器。

附件2：Fundamentals of Lightning ProtectionIntroductionLightning is a capricious, random and unpredictable event. Its' physical characteristics include current levels sometimes in excess of 400 kA, temperatures to 50,000 degrees F., and speeds approaching one third the speed of light. Globally, some 2000 on-going thunderstorms cause about 100 lightning strikes to earth each second. USA insurance company information shows one homeowner's damage claim for every 57 lightning strikes. Data about commercial, government, and industrial lightning-caused losses is not available. Annually in the USA lightning causes more than 26,000 fires with damage to property (NLSI estimates) in excess of $5-6 billion.The phenomenology of lightning strikes to earth, as presently understood, follows an approximate behavior:1. The downward Leaders from a thundercloud pulse towards earth seeking out active electrical ground targets.2. Ground-based objects (fences, trees, blades of grass, corners of buildings, people, lightning rods, etc., etc.) emit varying degrees of electric activityduring this event. Upward Streamers are launched from some of these objects. A few tens of meters off the ground, a "collection zone" is established according to the intensified local electrical field.3. Some Leader(s) likely will connect with some Streamer(s). Then, the "switch" is closed and the current flows. We see lightning.Lightning effects can be direct and/or indirect. Direct effects are from resistive (ohmic) heating, arcing and burning. Indirect effects are more probable. They include capacitive, inductive and magnetic behavior. Lightning "prevention" or "protection" (in an absolute sense) is impossible.A diminution of its consequences, together with incremental safety improvements, can be obtained by the use of a holistic or systematic hazard mitigation approach, described below in generic terms.Lightning RodsIn Franklin's day, lightning rods conducted current away from buildings to earth. Lightning rods, now known as air terminals, are believed to send Streamers upward at varying distances and times according to shape, height and other factors. Different designs of air terminals may be employed according to different protection requirements. For example, the utility industry prefers overhead shielding wires for electrical substations. In some cases, no use whatsoever of air terminals is appropriate (example: munitionsbunkers). Air terminals do not provide for safety to modern electronics within structures.Air terminal design may alter Streamer behavior. In equivalent e-fields, a blunt pointed rod is seen to behave differently than a sharp pointed rod. Faraday Cage and overhead shield designs produce yet other effects. Air terminal design and performance is a controversial and unresolved issue. Commercial claims of the "elimination" of lightning deserve a skeptical reception. Further research and testing is on-going in order to understand more fully the behavior of various air terminals.Downconductors, Bonding and ShieldingDownconductors should be installed in a safe manner through a known route, outside of the structure. They should not be painted, since this will increase impedance. Gradual bends (min. eight inch radius) should be adopted to avoid flashover problems. Building steel may be used in place of downconductors where practical as a beneficial part of the earth electrode subsystem.Bonding assures that all metal masses are at the same electrical potential.All metallic conductors entering structures (AC power, gas and water pipes, signal lines, HVAC ducting, conduits, railroad tracks, overhead bridge cranes, etc.) should be integrated electrically to the earth electrodesubsystem. Connector bonding should be thermal, not mechanical. Mechanical bonds are subject to corrosion and physical damage. Frequent inspection and ohmic resistance measuring of compression and mechanical connectors is recommended.Shielding is an additional line of defense against induced effects. It prevents the higher frequency electromagnetic noise from interfering with the desired signal. It is accomplished by isolation of the signal wires from the source of noise.GroundingThe grounding system must address low earth impedance as well as low resistance. A spectral study of lightning's typical impulse reveals both a high and a low frequency content. The high frequency is associated with an extremely fast rising "front" on the order of 10 microseconds to peak current. The lower frequency component resides in the long, high energy "tail" or follow-on current in the impulse. The grounding system appears to the lightning impulse as a transmission line where wave propagation theory applies.A single point grounding system is achieved when all equipment within the structure(s) are connected to a master bus bar which in turn is bonded to the external grounding system at one point only. Earth loops and differential risetimes must be avoided. The grounding system should be designed to reduce ac impedance and dc resistance. The shape and dimension of the earth termination system is more important a specific value of the earth electrode. The use of counterpoise or "crow's foot" radial techniques can lower impedance as they allow lightning energy to diverge as each buried conductor shares voltage gradients. Ground rings around structures are useful. They should be connected to the facility ground. Exothermic (welded) connectors are recommended in all circumstances.Cathodic reactance should be considered during the site analysis phase.Man-made earth additives and backfills are useful in difficult soils circumstances: they should be considered on a case-by-case basis where lowering grounding impedances are difficult an/or expensive by traditional means. Regular physical inspections and testing should be a part of an established preventive maintenance program.Transients and SurgesOrdinary fuses and circuit breakers are not capable of dealing with lightning-induced transients. Lightning protection equipment may shunt current, block energy from traveling down the wire, filter certain frequencies, clamp voltage levels, or perform a combination of these tasks. Voltage clamping devices capable of handling extremely high amperages of the surge, as well as reducing the extremely fast rising edge (dv/dt and di/dt) ofthe transient are recommended. Adopting a fortress defense against surges is prudent: protect the main panel (AC power) entry; protect all relevant secondary distribution panels; protect all valuable plug-in devices such as process control instrumentation, computers, printers, fire alarms, data recording & SCADA equipment, etc. Further, protect incoming and outgoing data and signal lines. Protect electric devices which serve the primary asset such as well heads, remote security alarms, CCTV cameras, high mast lighting, etc. HVAC vents which penetrate one structure from another should not be ignored as possible troublesome electrical pathways. Surge suppressors should be installed with minimum lead lengths to their respective panels. Under fast rise time conditions, cable inductance becomes important and high transient voltages can be developed across long leads.In all instances, use high quality, high speed, self-diagnosing protective components. Transient limiting devices may use a combination of arc gap diverters-metal oxide varistor-silicon avalanche diode technologies. Hybrid devices, using a combination of these technologies, are preferred. Know your clamping voltage requirements. Confirm that your vendor's products have been tested to rigid ANSI/IEEE/ISO9000 test standards. Avoidlow-priced, bargain products which proliferate the market (caveat emptor). DetectionLightning detectors, available at differing costs and technologies, sometimes are useful to provide early warning. An interesting application is when they are used to disconnect from AC line power and to engage standby power, before the arrival of lightning. Users should beware of over-confidence in such equipment which is not perfect and does not always acquire all lightning data.EducationLightning safety should be practiced by all people during thunderstorms. Preparedness includes: get indoors or in a car; avoid water and all metal objects; get off the high ground; avoid solitary trees; stay off the telephone. If caught outdoors during nearby lightning, adopt the Lightning Safety Position (LSP). LSP means staying away from other people, taking off all metal objects, crouching with feet together, head bowed, and placing hands on ears to reduce acoustic shock.Measuring lightning's distance is easy. Use the "Flash/Bang" (F/B) technique. For every count of five from the time of seeing the lightning stroke to hearing the associated thunder, lightning is one mile away. A F/B of 10 = 2 miles; a F/B of 20 = 4 miles, etc. Since the distance from Strike A to Strike B to Strike C can be as much as 5-8 miles. Be conservative and suspend activities when you first hear thunder, if possible. Do not resumeoutdoor activities until 20 minutes has past from the last observable thunder or lightning.Organizations should adopt a Lightning Safety Policy and integrate it into their overall safety plan.TestingModern diagnostic testing is available to mimic the performance of lightning conducting devices as well as to indicate the general route of lightning through structures. This testing typically is low power, 50 watt or less. It is traceable, but will not trip MOVs, gas tube arrestors, or other transient protection devices. Knowing the behavior of an event prior to occurrence is every businessman's earnest hope. With such techniques, lightning paths can be forecast reliably.Codes & StandardsThe marketplace abounds with exaggerated claims of product perfection. Frequently referenced codes and installation standards are incomplete, out dated and promulgated by commercial interests. On the other hand IEC, IEEE, MIL-STD, FAA, NASA and similar documents are supported by background engineering, the peer-review process, and are technical in nature.SummaryIt is important that all of the above subjects be considered in a lightning safety analysis. There is no Utopia in lightning protection. Lightning may ignore every defense man can conceive. A systematic hazard mitigation approach to lightning safety is a prudent course of action.References1.API 2003, Protection Against Ignitions Arising out of Static, Lightning,and Stray Currents, American Petroleum Institute, Washington DC,December 1991.2.Golde, G.H., Lightning, Academic Press, NY, 1977.3.Hasse, P., Overvoltage Protection of Low Voltage Systems, PeterPeregrinus Press, London, 1992.4.Hovath, Tibor, Computation of Lightning Protection, John Wiley, NY,1991.5.IEEE Std 1100, Powering and Grounding of Sensitive ElectronicEquipment, IEEE, NY, NY. 1992.6.KSC-STD-E-0012B, Standard for Bonding and Grounding, EngineeringDevelopment Directorate, John F. Kennedy Space Center, NASA, 1991.7.Morris, M.E., et.al., Rocket-Triggered Lightning Studies for the Protectionof Critical Assets, IEEE Transactions on Industry Applications, Vol. 30,No. 3, May/June 1994.8.Sunde, E.D. Earth Conduction Effects in Transmission Systems, D. VanNostrand Co., NY, 1949.9.Towne, D., Wave Phenomena, Dover Publications, NY.10.Uman, Martin, Lightning, Dover Publications, NY, 1984.附件1：外文资料翻译译文基础防雷简介闪电是一个反复无常，随机和不可预测的事件。

标准文档外文翻译院（系）专业班级姓名学号指导教师年月日Programmable designed for electro-pneumatic systemscontrollerJohn F.WakerlyThis project deals with the study of electro-pneumatic systems and the programmable controller that provides an effective and easy way to control the sequence of the pneumatic actuators movement and the states of pneumatic system. The project of a specific controller for pneumatic applications join the study of automation design and the control processing of pneumatic systems with the electronic design based on microcontrollers to implement the resources of the controller.1. IntroductionThe automation systems that use electro-pneumatic technology are formed mainly by three kinds of elements: actuators or motors, sensors or buttons and control elements like valves. Nowadays, most of the control elements used to execute the logic of the system were substituted by the Programmable Logic Controller (PLC). Sensors and switches are plugged as inputs and the direct control valves for the actuators are plugged as outputs. An internal program executes all the logic necessary to the sequence of the movements, simulates other components like counter, timer and control the status of the system.With the use of the PLC, the project wins agility, because it is possible to create and simulate the system as many times as needed. Therefore, time can be saved, risk of mistakes reduced and complexity can be increased using the same elements.A conventional PLC, that is possible to find on the market from many companies, offers many resources to control not only pneumatic systems, but all kinds of system that uses electrical components. The PLC can be very versatile and robust to be applied in many kinds of application in the industry or even security system and automation of buildings.Because of those characteristics, in some applications the PLC offers to much resources that are not even used to control the system, electro-pneumatic system is one of this kind of application. The use of PLC, especially for small size systems, can be very expensive for the automation project.An alternative in this case is to create a specific controller that can offer the exactly size and resources that the project needs [3, 4]. This can be made using microcontrollers as the base of this controller.The controller, based on microcontroller, can be very specific and adapted to only one kind of machine or it can work as a generic controller that can be programmed as a usual PLC and work with logic that can be changed. All these characteristics depend on what is needed and how much experience the designer has with developing an electronic circuit and firmware for microcontroller. But the main advantage of design the controller with the microcontroller is that the designer has the total knowledge of his controller, which makes it possible to control the size of the controller, change the complexity and the application of it. It means that the project gets more independence from other companies, but at the same time the responsibility of the control of the system stays at the designer hands2. Electro-pneumatic systemOn automation system one can find three basic components mentioned before, plus a logic circuit that controls the system. An adequate technique is needed to project the logic circuit and integrate all the necessary components to execute the sequence of movements properly.For a simple direct sequence of movement an intuitive method can be used [1, 5], but for indirect or more complex sequences the intuition can generate a very complicated circuit and signal mistakes. It is necessary to use another method that can save time of the project, makea clean circuit, can eliminate occasional signal overlapping and redundant circuits. The presented method is called step-by-step or algorithmic [1, 5], it is valid for pneumatic and electro-pneumatic systems and it was used as a base in this work.The method consists of designing the systems based on standard circuits made for each change on the state of the actuators, these changes are called steps.The first part is to design those kinds of standard circuits for each step, the next task is to link the standard circuits and the last part is to connect the control elements that receive signals from sensors, switches and the previous movements, and give the air or electricity to the supply lines of each step. In Figs. 1 and 2 the standard circuits are drawn for pneumatic and electro-pneumatic system [8]. It is possible to see the relations with the previous and the next steps.3. The method applied inside the controllerThe result of the method presented before is a sequence of movements of the actuator that is well defined by steps. It means that each change on the position of the actuators is a new state of the system and the transition between states is called step.The standard circuit described before helps the designer to define the states of the systems and to define the condition to each change betweenthe states. In the end of the design, the system is defined by a sequencethat never chances and states that have the inputs and the outputs well defined. The inputs are the condition for the transition and the outputs are the result of the transition.All the configuration of those steps stays inside of the microcontroller and is executed the same way it was designed. The sequences of strings are programmed inside the controller with 5 bytes; each string has the configuration of one step of the process. There are two bytes for the inputs, one byte for the outputs and two more for the other configurations and auxiliary functions of the step. After programming, this sequence of strings is saved inside of a non-volatile memory of the microcontroller, so they can be read and executed.The controller task is not to work in the same way as a conventional PLC, but the purpose of it is to be an example of a versatile controller that is design for an specific area. A conventional PLC process the control of the system using a cycle where it makes an image of the inputs, execute all the conditions defined by the configuration programmed inside, and then update the state of the outputs. This controller works in a different way, where it read the configuration of the step, wait the condition of inputs to be satisfied, then update the state or the outputs and after that jump to the next step and start the process again.It can generate some limitations, as the fact that this controller cannot execute, inside the program, movements that must be repeated for some time, but this problem can be solved with some external logic components. Another limitation is that the controller cannot be applied on systems that have no sequence. These limitations are a characteristic of the system that must be analyzed for each application.4. Characteristics of the controllerThe controller is based on the MICROCHIP microcontroller PIC16F877 [6,7] with 40 pins, and it has all the resources needed for thisproject .It has enough pins for all the components, serial communication implemented in circuit, EEPROM memory to save all the configuration of the system and the sequence of steps. For the execution of the main program, it offers complete resources as timers and interruptions.The list of resources of the controller was created to explore all the capacity of the microcontroller to make it as complete as possible. During the step, the program chooses how to use the resources reading the configuration string of the step. This string has two bytes for digital inputs, one used as a mask and the other one used as a value expected. One byte is used to configure the outputs value. One bytes more is used for the internal timer , the analog input or time-out. The EEPROM memory inside is 256 bytes length that is enough to save the string of the steps, with this characteristic it is possible to save between 48 steps （Table 1）.The controller (Fig.3) has also a display and some buttons that are used with an interactive menu to program the sequence of steps and other configurations.4.1. Interaction componentsFor the real application the controller must have some elements to interact with the final user and to offer a complete monitoring of the system resources that are available to the designer while creating the logic control of the pneumatic system (Fig.3):•Interactive mode of work; function available on the main program for didactic purposes, the user gives the signal to execute the step. •LCD display, which shows the status of the system, values of inputs, outputs, timer and statistics of the sequence execution.•Beep to give important alerts, stop, start and emergency.• Leds to show power on and others to show the state of inputs and outputs.4.2. SecurityTo make the final application works property, a correct configuration to execute the steps in the right way is needed, but more then that itmust offer solutions in case of bad functioning or problems in the execution of the sequence. The controller offers the possibility to configure two internal virtual circuits that work in parallel to the principal. These two circuits can be used as emergency or reset buttons and can return the system to a certain state at any time [2]. There are two inputs that work with interruption to get an immediate access to these functions. It is possible to configure the position, the buttons and the value of time-out of the system.4.3. User interfaceThe sequence of strings can be programmed using the interface elements of the controller. A Computer interface can also be used to generate the user program easily. With a good documentation the final user can use the interface to configure the strings of bytes that define the steps of the sequence. But it is possible to create a program with visual resources that works as a translator to the user, it changes his work to the values that the controller understands.To implement the communication between the computer interface and the controller a simple protocol with check sum and number of bytes is the minimum requirements to guarantee the integrity of the data.4.4. FirmwareThe main loop works by reading the strings of the steps from the EEPROM memory that has all the information about the steps.In each step, the status of the system is saved on the memory and it is shown on the display too. Depending of the user configuration, it can use the interruption to work with the emergency circuit or time-out to keep the system safety. In Fig.4,a block diagram of micro controller main program is presented.5. Example of electro-pneumatic systemThe system is not a representation of a specific machine, but it is made with some common movements and components found in a real one. The system is composed of four actuators. The actuators A, B and C are double acting and D-single acting. Actuator A advances and stays in specified position till the end of the cycle, it could work fixing an object to the next action for example (Fig. 5) , it is the first step. When A reaches the end position, actuator C starts his work together with B, making as many cycles as possible during the advancing of B. It depends on how fastactuator B is advancing; the speed is regulated by a flowing control valve. It was the second step. B and C are examples of actuators working together, while B pushes an object slowly, C repeats its work for some time.When B reaches the final position, C stops immediately its cycle and comes back to the initial position. The actuator D is a single acting one with spring return and works together with the back of C, it is the third step. D works making very fast forward and backward movement, just one time. Its backward movement is the fourth step. D could be a tool to make a hole on the object.When D reaches the initial position, A and B return too, it is the fifth step.Fig. 6 shows the first part of the designing process where all the movements of each step should be defined [2]. (A+) means that the actuator A moves to the advanced position and (A−) to the initial position. The movements that happen at the same time are joined together in the same step. The system has five steps.These two representations of the system (Figs. 5 and 6) together are enough to describe correctly all the sequence. With them is possible to design the whole control circuit with the necessary logic components. But till this time, it is not a complete system, because it is missing some auxiliary elements that are not included in this draws because they work in parallel with the main sequence.These auxiliary elements give more function to the circuit and are very important to the final application; the most important of them is the parallel circuit linked with all the others steps. That circuit should be able to stop the sequence at any time and change the state of the actuators to a specific position. This kind of circuit can be used as a reset or emergency buttons.The next Figs. 7 and 8 show the result of using the method without the controller. These pictures are the electric diagram of the control circuit of the example, including sensors, buttons and the coils of the electrical valves.The auxiliary elements are included, like the automatic/manual switcher that permit a continuous work and the two start buttons that make the operator of a machine use their two hands to start the process, reducing the risk of accidents.6. Changing the example to a user programIn the previous chapter, the electro-pneumatic circuits were presented, used to begin the study of the requires to control a system that work with steps and must offer all the functional elements to be used in a real application. But, as explained above, using a PLC or this specific controller, the control becomes easier and the complexity can be increasealso.Table 2 shows a resume of the elements that are necessary to control the presented example.With the time diagram, the step sequence and the elements of the system described in Table 2 and Figs. 5 and 6 it is possible to create the configuration of the steps that can be sent to the controller (Tables 3 and 4).While using a conventional PLC, the user should pay attention to the logic of the circuit when drawing the electric diagram on the interface (Figs. 7 and 8), using the programmable controller, described in this work, the user must know only the concept o f the method and program only the configuration of each step.It means that, with a conventional PLC, the user must draw the relationbetween the lines and the draw makes it hard to differentiate the steps of the sequence. Normally, one needs to execute a simulation on the interface to find mistakes on the logicThe new programming allows that the configuration of the steps be separated, like described by the method. The sequence is defined by itself and the steps are described only by the inputs and outputs for each step.The structure of the configuration follows the order:1-byte: features of the step;2-byte: mask for the inputs;3-byte: value expected on the inputs;4-byte: value for the outputs;5-byte: value for the extra function.Table 5 shows how the user program is saved inside the controller, this is the program that describes the control of the example shown before.The sequence can be defined by 25 bytes. These bytes can be dividedin five strings with 5 bytes each that define each step of the sequence (Figs. 9 and 10).7. ConclusionThe controller developed for this work (Fig. 11) shows that it is possible to create a very useful programmable controller based on microcontroller. External memories or external timers were not used in case to explore the resources that the microcontroller offers inside. Outside the microcontroller, there are only components to implement the outputs, inputs, analog input, display for the interface and the serial communication.Using only the internal memory, it is possible to control a pneumatic system that has a sequence with 48 steps if all the resources for all steps are used, but it is possible to reach sixty steps in the case of a simpler system.The programming of the controller does not use PLC languages, but a configuration that is simple and intuitive. With electro-pneumatic system, the programming follows the same technique that was used before to design the system, but here the designer work s directly with the states or steps of the system.With a very simple machine language the designer can define all the configuration of the step using four or five bytes. It depends only on his experience to use all the resources of the controller.The controller task is not to work in the same way as a commercial PLC but the purpose of it is to be an example of a versatile controller that is designed for a specific area. Because of that, it is not possible to say which one works better; the system made with microcontroller is an alternative that works in a simple way.应用于电气系统的可编程序控制器约翰 F.维克里此项目主要是研究电气系统以及简单有效的控制气流发动机的程序和气流系统的状态。

Circuit breaker断路器Compressed air circuit breaker is a mechanical switch equipment, can be i 空气压缩断路器是一种机械开关设备，能够在n normal and special conditions breaking current (such as short circuit cur 正常和特殊情况下开断电流（比如说短路电流）。

rent). For example, air circuit breaker, oil circuit breaker, interference circ 例如空气断路器、油断路器，干扰电路的导体uit conductor for the application of the safety and reliability of the circuit 干扰电路的导体因该安全可靠的应用于其中，breaker, current in arc from is usually divided into the following grades: a 电流断路器按灭弧远离通常被分为如下等级：ir switch circuit breaker, oil circuit breaker, less oil circuit breaker, compr 空气开关断路器、油断路器、少油断路器、压缩空essed air circuit breaker, a degaussing of isolating switch, six sulfur hexaf 气断路器、具有消磁性质的隔离开关、六氟luoride circuit breaker and vacuum breaker. Their parameters of voltage, 化硫断路器和真空断路器。

他们的参数有电压等级、current, insulation level of breaking capacity, instantaneous voltage off ti 开断容量的电流、绝缘等级开断时间的瞬时电压恢复和me of recovery and a bombing. Breaker plate usually include: 1 the maxi 轰炸时间。

文献信息：文献标题：Speech Recognition Using Vector Quantization through Modified K-meansLBG Algorithm（基于改进矢量量化K-均值LBG算法的语音识别）国外作者：Balwant A.Sonkamble，Dharmpal Doye文献出处：《Computer Engineering and Intelligent Systems》, 2012, 7(3) 字数统计：英文2389单词，13087字符；中文3968汉字外文文献：Speech Recognition Using Vector Quantization throughModified K-meansLBG AlgorithmAbstract In the Vector Quantization, the main task is to generate a good codebook. The distortion measure between the original pattern and the reconstructed pattern should be minimum. In this paper, a proposed algorithm called Modified K-meansLBG algorithm used to obtain a good codebook. The system has shown good performance on limited vocabulary tasks.Keywords: K-means algorithm, LBG algorithm, Vector Quantization, Speech Recognition1.IntroductionThe natural way of communication among human beings is through speech. Many human beings are exchanging the information through mobile phones as well as other communication tools in a real manner [L. R. Rabiner et al., 1993]. The Vector Quantization (VQ) is the fundamental and most successful technique used in speech coding, image coding, speech recognition, and speech synthesis and speaker recognition [S. Furui, 1986]. These techniques are applied firstly in the analysis of speech where the mapping of large vector space into a finite number of regions in thatspace. The VQ techniques are commonly applied to develop discrete or semi-continuous HMM based speech recognition system.In VQ, an ordered set of signal samples or parameters can be efficiently coded by matching the input vector to a similar pattern or codevector (codeword) in a predefined codebook [[Tzu-Chuen Lu et al., 2010].The VQ techniques are also known as data clustering methods in various disciplines. It is an unsupervised learning procedure widely used in many applications. The data clustering methods are classified as hard and soft clustering methods. These are centroid-based parametric clustering techniques based on a large class of distortion functions known as Bregman divergences [Arindam Banerjee et al., 2005].In the hard clustering, each data point belongs to exactly one of the partitions in obtaining the disjoint partitioning of the data whereas each data point has a certain probability of belonging to each of the partitions in soft clustering. The parametric clustering algorithms are very popular due to its simplicity and scalability. The hard clustering algorithms are based on the iterative relocation schemes. The classical K-means algorithm is based on Euclidean distance and the Linde-Buzo-Gray (LBG) algorithm is based on the Itakura-Saito distance. The performance of vector quantization techniques depends on the existence of a good codebook of representative vectors.In this paper, an efficient VQ codebook design algorithm is proposed known as Modified K-meansLBG algorithm. This algorithm provides superior performance as compared to classical K-means algorithm and the LBG algorithm. Section-2 describes the theoretical details of VQ. Section-3 elaborates LBG algorithm. Section-4 explains classical K-means algorithm. Section -5 emphasizes proposed modified K-meansLBG algorithm. The experimental work and results are discussed in Section-6 and the concluding remarks made at the end of the paper.2.Vector QuantizationThe main objective of data compression is to reduce the bit rate for transmission or data storage while maintaining the necessary fidelity of the data. The feature vectormay represent a number of different possible speech coding parameters including linear predictive coding (LPC) coefficients, cepstrum coefficients. The VQ can be considered as a generalization of scalar quantization to the quantization of a vector. The VQ encoder encodes a given set of k-dimensional data vectors with a much smaller subset. The subset C is called a codebook and its elements i C are called codewords, codevectors, reproducing vectors, prototypes or design samples. Only the index i is transmitted to the decoder. The decoder has the same codebook as the encoder, and decoding is operated by table look-up procedure.The commonly used vector quantizers are based on nearest neighbor called V oronoi or nearest neighbour vector quantizer. Both the classical K-means algorithm and the LBG algorithm belong to the class of nearest neighbor quantizers.A key component of pattern matching is the measurement of dissimilarity between two feature vectors. The measurement of dissimilarity satisfies three metric properties such as Positive definiteness property, Symmetry property and Triangular inequality property. Each metric has three main characteristics such as computational complexity, analytical tractability and feature evaluation reliability. The metrics used in speech processing are derived from the Minkowski metric [J. S. Pan et al. 1996]. The Minkowski metric can be expressed as∑=-=k i p i i p y xp Y X D 1),(Where },...,,{21k x x x X = and },...,,{21k y y y Y = are vectors and p is the order of the metric.The City block metric, Euclidean metric and Manhattan metric are the special cases of Minkowski metric. These metrics are very essential in the distortion measure computation functions.The distortion measure is one which satisfies only the positive definiteness property of the measurement of dissimilarity. There were many kinds of distortion measures including Euclidean distance, the Itakura distortion measure and the likelihood distortion measure, and so on.The Euclidean metric [Tzu-Chuen Lu et al., 2010] is commonly used because it fits the physical meaning of distance or distortion. In some applications division calculations are not required. To avoid calculating the divisions, the squared Euclidean metric is employed instead of the Euclidean metric in pattern matching.The quadratic metric [Marcel R. Ackermann et al., 2010] is an important generalization of the Euclidean metric. The weighted cepstral distortion measure is a kind of quadratec metric. The weighted cepstral distortion key feature is that it equalizes the importance in each dimension of cepstrum coefficients. In the speech recognition, the weighted cepstral distortion can be used to equalize the performance of the recognizer across different talkers. The Itakura-Saito distortion [Arindam Banerjee et al., 2005] measure computes a distortion between two input vectors by using their spectral densities.The performance of the vector quantizer can be evaluated by a distortion measureD which is a non-negative cost )ˆ,(j j X X Dassociated with quantizing any input vector j Xwith a reproduction vecto j X ˆ. Usually, the Euclidean distortion measure is used. The performance of a quantizer is always qualified by an average distortion)]ˆ,([j j v X X D E Detween the input vectors and the final reproduction vectors, where E represents the expectation operator. Normally, the performance of the quantizer will be good if the average distortion is small.Another important factor in VQ is the codeword search problem. As the vector dimension increases accordingly the search complexity increases exponentially, this is a major limitation of VQ codeword search. It limits the fidelity of coding for real time transmission.A full search algorithm is applied in VQ encoding and recognition. It is a time consuming process when the codebook size is large.In the codeword search problem, assigning one codeword to the test vector means the smallest distortion between the codeword and the test vector among all codewords. Given one codeword t C and the test vector X in the k-dimensional space,the distortion of the squared Euclidean metric can be expressed as follows:∑=-=ki i t i t c x C X D 12)(),(Where },......,,{21k t t t t c c c C = and },......,,{2,1k x x x X =There are three ways of generating and designing a good codebook namely the random method, the pair-wise nearestneighbor clustering and the splitting method. A wide variety of distortion functions, such as squared Euclidean distance, Mahalanobis distance, Itakura-Saito distance and relative entropy have been used for clustering. There are three major procedures in VQ, namely codebook generation, encoding procedure and decoding procedure. The LBG algorithm is an efficient VQ clustering algorithm. This algorithm is based either on a known probabilistic model or on a long training sequence of data.3.Linde –Buzo –Gray (LBG) algorithmThe LBG algorithm is also known as the Generalised Lloyd algorithm (GLA). It is an easy and rapid algorithm used as an iterative nonvariational technique for designing the scalar quantizer. It is a vector quantization algorithm to derive a good codebook by finding the centroids of partitioned sets and the minimum distortion partitions. In LBG , the initial centroids are generated from all of the training data by applying the splitting procedure. All the training vectors are incorporated to the training procedure at each iteration. The GLA algorithm is applied to generate the centroids and the centroids cannot change with time. The GLA algorithm starts from one cluster and then separates this cluster to two clusters, four clusters, and so on until N clusters are generated, where N is the desired number of clusters or codebook size. Therefore, the GLA algorithm is a divisive clustering approach. The classification at each stage uses the full-search algorithm to find the nearest centroid to each vector. The LBG is a local optimization procedure and solved through various approaches such as directed search binary-splitting, mean-distance-ordered partial codebook search [Linde et al., 1980, Modha et al., 2003], enhance LBG , GA-based algorithm[Tzu-Chuen Lu et al., 2010, Chin-Chen Chang et al. 2006], evolution-based tabu search approach [Shih-Ming Pan et al., 2007], and codebook generation algorithm[Buzo et al., 1980].In speech processing, vector quantization is used for instance of bit stream reduction in coding or in the tasks based on HMM. Initialization is an important step in the codebook estimation. Two approaches used for initialization are Random initialization, where L vectors are randomly chosen from the training vector set and Initialization from a smaller coding book by splitting the chosen vectors.The detailed LBG algorithm using unknown distribution is described as given below: Step 1: Design a 1-vector codebook. Set m=1. Calculate centroid∑==T j j X TC 111 Where T is the total number of data vectors.Step 2: Double the size of the codebook by splitting.Divide each centroid i C into two close vectors )1(12δ+⨯=-i i C C and m i C C i i ≤≤-⨯=1),1(2δ. Here δ is a small fixed perturbation scalar.Let m=2m . Set n=0 , here n is the iterative time.Step 3: Nearest-Neighbor Search.Find the nearest neighbor to each data vector. Put j Xin the partitioned set i P if i C is the nearest neighbor to j X .Step 4: Find Average Distortion.After obtaining the partitioned sets)1,(m i P P i ≤≤=, Set n=n+1 Calculate the overall average distortion∑∑--=m i T j i i j n i C D TD 11)(),(1 Where },......,,{)()(2)(1i T i i i iX X X P =Step 5: Centroid Update.Find centroids of all disjoint partitioned sets i P by∑-=i T j i j i i X T C 1)(1Step 6: Iteration 1.If ε>--n n n D D D /)(1 , go to step 3;otherwise go to step 7 and ε is a threshold.Step 7: Iteration 2.If m=N , then take the codebook i C as the final codebook; otherwise, go to step 2.Here N is the codebook size.The LBG algorithm has limitations like the quantized space is not optimized at each iteration and the algorithm is very sensitive to initial conditions.4.Classical K-means AlgorithmThe K-means algorithm is proposed by MacQueen in 1967. It is a well known iterative procedure for solving the clustering problems. It is also known as the C-means algorithm or basic ISODATA clustering algorithm. It is an unsupervised learning procedure which classifies the objects automatically based on the criteria that minimum distance to the centroid. In the K-means algorithm, the initial centroids are selected randomly from the training vectors and the training vectors are added to the training procedure one at a time. The training procedure terminates when the last vector is incorporated. The K-means algorithm is used to group data and the groups can change with time. The algorithm can be applied to VQ codebook design. The K-means algorithm can be described as follows:Step 1: Randomly select N training data vectors as the initial codevectors N i C i ,......,2,1,=from T training data vectors. Step 2: For each training data vector T j X j ,......,2,1,= assign j X to thepartitioned set i S if ),(min arg i j i C X D i =Step 3: Compute the centroid of the partitioned set that is codevector using ∑∈=i j S X j i i XS C 1Where i S denotes the number of training data vectors in the partitioned seti S . If there is no change in the clustering centroids, then terminate the program; otherwise, go to step 2.There are various limitations of K-means algorithm. Firstly, it requires large data to determine the cluster. Secondly, the number of cluster, K, must be determined beforehand. Thirdly, if the number of data is a small it difficult to find real cluster and lastly, as per assumption each attribute has the same weight and it quite difficult to knows which attribute contributes more to the grouping process.It is an algorithm to classify or to group objects based on attributes/features into K number of group. K is positive integer number. The grouping is done by minimizing the sum of squares of distances between data and the corresponding cluster centroid. The main aim of K-mean clustering is to classify the data. In practice, the number of iterations is generally much less than the number of points.5.Proposed Modified K-meansLBG AlgorithmThe proposed algorithms objective is to overcome the limitations of LBG algorithm and K-means algorithm. The proposed modified KmeansLBG algorithm is the combination of advantages of LBG algorithm and K-means algorithms. The KmeansLBG algorithm is described as given below:Step 1: Randomly select N training data vectors as the initial codevectors. Step 2: Calculate the no. of centroids.Step 3: Double the size of the codebook by splitting. Step 4: Nearest-Neighbor Search.Step 5: Find Average Distortion.Step 6: Update the centroid till there is no change in the clustering centroids,terminate the program otherwise go to step 1.6.Experimentation and ResultsThe TI46 database [NIST, 1991] is used for experimentation. There are 16 speakers from them 8 male speakers and 8 female speakers. The numbers of replications are 26 for utterance by each person. The total database size is 4160 utterances of which 1600 samples were used for training and remaining samples are used for testing of 10 words that are numbers in English 1 to 9 and 0 are sampled at a rate of 8000 Hz. A feature vector of 12-dimensional Linear Predicting Coding Cepstrum coefficients was obtained and provided as an input to vector quantization to find codewords for each class.There are five figures shows comparative graphs of the distortion measure obtained using LBG algorithm and K-means algorithm and proposed K-meansLBG algorithm. The distortion measure obtained by the proposed algorithm is smallest as compared to the K-means algorithm and the LBG algorithm.The proposed modified KmeanLBG algorithm gives minimum distortion measure as compared to K-means algorithm and LBG algorithm to increase the performance of the system. The smallest measure gives superior performance as compared to both the algorithms as is increased by about 1% to 4 % for every digit.7.ConclusionThe Vector Quantization techniques are efficiently applied in the development of speech recognition systems. In this paper, the proposed a novel vector quantization algorithm called K-meansLBG algorithm. It is used efficiently to increase the performance of the speech recognition system. The recognition accuracy obtained using K-meansLBG algorithm is better as compared to K-means and LBG algorithm. The average recognition accuracy of K-meansLBG algorithm is more than 2.55% using K-means algorithm while the average recognition accuracy of K-meansLBG algorithm is more than 1.41% using LBG algorithm.中文译文：基于改进矢量量化K-均值LBG算法的语音识别摘要矢量量化的主要任务是产生良好的码本。

本科毕业设计（论文）中英文对照翻译院（系部）电气工程与自动化学院专业名称电气工程及其自动化年级班级03级2班学生姓名指导老师电力系统1 电力的技术特点电力具有独特的技术特点，这使得电力工业具有独特的行业特点。

1.无形性。

用户不能用人体感官直接察觉千瓦时的用电量。

2.质量。

供电质量可由供电连续性或供电可靠性、在标准电压等级下的电压均等性、交流电压频率的正确不变性来度量。

3.电力的贮存。

与大多数行业不同，电力部门必须随时根据用电的需求生产出电力来，因为电能无法贮存。

4.对供电负责。

电由电力部门输送到用户，因此必须对安全、可靠供电负责。

5.对公众的安全。

电力部门须对公众及其技术人员提供稳妥的保护。

2 电力系统的规划预期到电力部门的供电负荷将持续增长，电力系统的容量也持续增大。

远期规划主要是保证这种扩建在技术上是适宜的，在造价上是合理的，与增长模式是相符的。

远期规划者碰到的困难包括：不同地域和不同时间负荷增长的不确定性、新发明新技术发展的可能性。

优异的系统规划要努力做到全系统设计的最优化，而不能为了系统某部分造价的最小化而不顾其它部分的影响。

近年来，已经强调了规划和运行的经济性。

现在则越来越强调可靠性和环境方面的因素。

在作出规划前，须要仔细考虑许多因素：（1）设备的决策具有远期效应，这需要15—25年的预期和研究。

（2）有许多发电途径可选择：核电、基荷火电、中等规模燃气轮机发电或水电，以及大型、中型、小型电厂和各种形式的蓄能。

（3）有多种送电途径可选择，例如由交流或直流，架空线或地下电缆送电并有各种电压等级。

（4）规划决策受负荷管理技术和负荷模式的影响。

（5）有关因素存在不确定性。

如将来燃料价格货币的利率资金的来源设备的强迫停运率新技术环境的要求。

3 电力分配3.1 最初的分配系统发电厂和最后的各支路之间的分配线路叫做最初的分配系统。

在这两个电力系统之间传输有多种方法. 其中最常见的两种方法是辐射式和环绕式。

电气工程及其自动化专业英语翻译（精选多篇）第一篇：电气工程及其自动化专业英语翻译Electric Power Systems.The modern society depends on the electricity supply more heavily than ever before.It can not be imagined what the world should be if the electricity supply were interrupted all over the world.Electric power systems(or electric energy systems), providing electricity to the modern society, have become indispensable components of the industrial world.The first complete electric power system(comprising a generator, cable, fuse, meter, and loads)was built by Thomas Edison – the historic Pearl Street Station in New York City which began operation in September 1882.This was a DC system consisting of a steam-engine-driven DC generator supplying power to 59 customers within an area roughly 1.5 km in radius.The load, which consisted entirely of incandescent lamps, was supplied at 110 V through an underground cable system..Within a few years similar systems were in operation in most large cities throughout the world.With the development of motors by Frank Sprague in 1884, motor loads were added to such systems.This was the beginning of what would develop into one of the largest industries in the world.In spite of the initial widespread use of DC systems, they were almost completely superseded by AC systems.By 1886, the limitations of DC systems were becoming increasingly apparent.They could deliver power only a short distance from generators.To keep transmission power losses(I 2 R)and voltage drops to acceptable levels, voltage levels had to be high for long-distance power transmission.Such high voltages were not acceptable for generation and consumption of power;therefore, a convenient means for voltage transformationbecame a necessity.The development of the transformer and AC transmission by L.Gaulard and JD Gibbs of Paris, France, led to AC electric power systems.In 1889, the first AC transmission line in North America was put into operation in Oregon between Willamette Falls and Portland.It was a single-phase line transmitting power at 4,000 V over a distance of 21 km.With the development of polyphase systems by Nikola Tesla, the AC system became even more attractive.By 1888, Tesla held several patents on AC motors, generators, transformers, and transmission systems.Westinghouse bought the patents to these early inventions, and they formed the basis of the present-day AC systems.In the 1890s, there was considerable controversy over whether the electric utility industry should be standardized on DC or AC.By the turn of the century, the AC system had won out over the DC system for the following reasons:（1）Voltage levels can be easily transformed in AC systems, thusproviding the flexibility for use of different voltages for generation, transmission, and consumption.（2）AC generators are much simpler than DC generators.（3）AC motors are much simpler and cheaper than DC motors.The first three-phase line in North America went into operation in 1893——a 2,300 V, 12 km line in southern California.In the early period of AC power transmission, frequency was not standardized.This poses a problem for interconnection.Eventually 60 Hz was adopted as standard in North America, although 50 Hz was used in many other countries.The increasing need for transmitting large amounts of power over longer distance created an incentive to use progressively high voltage levels.To avoid the proliferation of anunlimited number of voltages, the industry has standardized voltage levels.In USA, the standards are 115, 138, 161, and 230 kV for the high voltage(HV)class, and 345, 500 and 765 kV for the extra-high voltage(EHV)class.In China, the voltage levels in use are 10, 35, 110 for HV class, and 220, 330(only in Northwest China)and500 kVforEHVclass.Thefirst750kVtransmission line will be built in the near future in Northwest China.With the development of the AC/DC converting equipment, high voltage DC(HVDC)transmission systems have become more attractive and economical in special situations.The HVDC transmission can be used for transmission of large blocks of power over long distance, and providing an asynchronous link between systems where AC interconnection would be impractical because of system stability consideration or because nominal frequencies of the systems are different.The basic requirement to a power system is to provide an uninterrupted energy supply to customers with acceptable voltages and frequency.Because electricity can not be massively stored under a simple and economic way, the production and consumption of electricity must be done simultaneously.A fault or misoperation in any stages of a power system may possibly result in interruption of electricity supply to the customers.Therefore, a normal continuous operation of the power system to provide a reliable power supply to the customers is of paramount importance.Power system stability may be broadly defined as the property of a power system that enables it to remain in a state of operating equilibrium under normal operating conditions and to regain an acceptable state of equilibrium after being subjected to a disturbance..Instability in a power system may be manifested in many different ways depending on the system configurationand operating mode.Traditionally, the stability problem has been one of maintaining synchronous operation.Since power systems rely on synchronous machines for generation of electrical power, a necessary condition for satisfactory system operation is that all synchronous machines remain in synchronism or, colloquially “in step”.This asp ect of stability is influenced by the dynamics of generator rotor angles and power-angle relationships, and then referred to “ rotor angle stability ”译文：电力系统现代社会比以往任何时候更多地依赖于电力供应。

电子电气工程及其自动化外文翻译外文文献基础防雷2.If ___ with an active ground target。

an upwardLeader is initiated from the ground towards the cloud.3.When the two Leaders meet。

a channel is established forthe ___.4.The lightning current follows the established channel。

which can beup to several miles long.5.The current heats the air along the channel to incandescence。

___.6.The current can cause ___。

includingbuildings。

trees。

and people.___ through the use of lightning rods。

surge protectors。

___。

___.Lightning rods are the most common form of ___ lightning strikes。

___ for the current to follow。

diverting it away from the structure and into the ground.___ ground。

___.___。

___.___。

___ rods。

surge protectors。

and grounding systems。

it is possible to mitigate the effects of lightning strikes and ce the risk of damage and injury。

While lightning remains a us and unpredictable event。

电气自动化英文文献Electrical Automation: A Comprehensive Analysis.Introduction.Electrical automation is the use of automated systems to control electrical processes in various industries. It encompasses the design, implementation, and maintenance of automated systems to enhance efficiency, safety, and productivity. This technology finds applications in numerous sectors, including manufacturing, energy, healthcare, transportation, and residential settings.Components of Electrical Automation Systems.1. Sensors: Detects and measures various physical parameters such as temperature, pressure, flow, and position.2. Controllers: Analyzes sensor data, makes decisions,and activates actuators based on programmed instructions.3. Actuators: Physical devices that perform actions in response to controller commands, such as opening valves, starting motors, or moving conveyors.4. Communication Network: Connects sensors, controllers, and actuators, enabling data exchange and coordination.5. Human-Machine Interface (HMI): Provides an interface for operators to interact with the automated system and monitor its performance.Benefits of Electrical Automation.1. Increased Efficiency: Automates repetitive tasks, reducing human errors and improving productivity.2. Enhanced Safety: Eliminates the need for manual intervention in hazardous environments, reducing the riskof accidents.3. Improved Quality: Ensures consistent and accurate control of processes, leading to higher quality products.4. Reduced Costs: Optimizes energy usage, reduces maintenance expenses, and eliminates labor costs associated with manual operations.5. Increased Flexibility: Allows for rapid reconfiguration of automated systems to adapt to changing requirements or product specifications.Applications of Electrical Automation.1. Manufacturing: Automated assembly lines, robotic workstations, and inventory management systems.2. Energy: Smart grids, renewable energy systems, and energy efficiency management.3. Healthcare: Automated medical devices, patient monitoring systems, and hospital automation.4. Transportation: Vehicle control systems, traffic management systems, and automated logistics.5. Residential Settings: Home automation systems for lighting, temperature control, and security.Challenges in Electrical Automation.1. Complexity: Designing and integrating complex automated systems requires advanced engineering skills and specialized software.2. Cybersecurity: Automated systems can be vulnerable to cyberattacks, requiring robust security measures.3. Maintenance and Troubleshooting: Regular maintenance and skilled technicians are crucial to ensure thereliability and uptime of automated systems.4. Initial Investment: Implementing electrical automation systems can involve significant upfront costs, requiring careful planning and justification of theinvestment.5. Displacement of Workforce: Automation can lead to job displacement, necessitating training and upskilling programs for displaced workers.Future Trends in Electrical Automation.1. Artificial Intelligence (AI) and Machine Learning: Enabling predictive analytics, self-optimization, and autonomous decision-making.2. Internet of Things (IoT): Connecting automated systems to the internet for remote monitoring, data analytics, and cloud-based services.3. Digital Twins: Creating virtual models of automated systems for simulation, testing, and real-time monitoring.4. Edge Computing: Processing data on-site to reduce latency and improve system responsiveness.5. Increased Adoption in Emerging Industries: Expanding applications in sectors such as agriculture, mining, and construction.Conclusion.Electrical automation is a transformative technology that has revolutionized various industries, driving efficiency, safety, quality, and cost savings. As technology continues to advance, the applications and possibilities of electrical automation are bound to grow exponentially, contributing to further innovation and progress across numerous sectors.。