Negotiating expert status: who gets taken seriously

A lay person may listen puzzled as a specialist in a public hearing discusses a technical point. Similarly, a challenging question from a technically knowledgeable member of the audience may be difficult to fathom. Failure to understand what a speaker discusses-despite one's interest in a topic-can cause frustration, anger and despair. It makes a listener wonder why they are there trying to engage, and why technical specialists persist in such a style of presentation. Breakdowns in communication between technical and nontechnical people are linked to the concept of “expert”. This link involves the process of the “negotiation of expert status”; this refers to the social construction of the role of the “expert” by the participants in a conversation. The term “negotiation” refers to the sometimes subtle and sometimes overtly contentious nature of a debate about who deserves to be listened to as a voice of authority on a particular topic     

Expert system for dispatch control in restoration of ehv power system after complete blackout

Present-day power systems operate with high reliability, and it is rare that a blackout will extend over an entire system swiftly and securely. This paper considers automatic power supply to loads after a complete blackout of a system. First, taking into account characteristics of generators, loads, and initial power sources, a method is proposed of allocating several generators to each load in parallel to the system and supplying power to the load sequentially. Second, to remove the imbalance between supply and demand of power, a method is proposed of adjusting the amount of supply and generation according to a present imbalance and the sum of past ones. Third, to automatically issue orders for start-up, parallel, follow-up, stand-by, and stoppage of generators, several rules for each power station are set and an expert system is made based on them. Finally, the expert system is applied to a model power system, and it is verified that it can restore loads without any trouble for a complete blackout which occur at any time of a day and in any restoration pattern.     

Smooth approximation and forecasting of load duration curves

The purpose of this paper is to develop a methodology for forecasting a load duration curve. The approach adopted in the development is to estimate a load duration curve as a combined linear-exponential function and relate the coefficients of this function to a set of economic and weather related variables. This relationship allows one to forecast the coefficients which are in turn used to provide a forecast of the coefficients of interest.The model presented, for a specific set of data, forecasts well and presents a substantial improvement over existing approaches to obtaining future load duration curves.     

Unit commitment using Lagrangian relaxation and particle swarm optimization

Unit commitment (UC) is a NP-hard nonlinear mixed-integer optimization problem. This paper proposes ELRPSO, an algorithm to solve the UC problem using Lagrangian relaxation (LR) and particle swarm optimization (PSO). ELRPSO employs a state-of-the-art powerful PSO variant called comprehensive learning PSO to find a feasible near-optimal UC schedule. Each particle represents Lagrangian multipliers. The PSO uses a low level LR procedure, a reserve repairing heuristic, a unit decommitment heuristic, and an economic dispatch heuristic to obtain a feasible UC schedule for each particle. The reserve repairing heuristic addresses the spinning reserve and minimum up/down time constraints simultaneously. Moreover, the reserve repairing and unit decommitment heuristics consider committing/decommitting a unit for a consecutive period of hours at a time in order to reduce the total startup cost. Each particle is initialized using the Lagrangian multipliers obtained from a LR that iteratively updates the multipliers through an adaptive subgradient heuristic, because the multipliers obtained from the LR tend to be close to the optimal multipliers and have a high potential to lead to a feasible near-optimal UC schedule. Numerical results on test thermal power systems of 10, 20, 40, 60, 80, and 100 units demonstrate that ELRPSO is able to find a low-cost UC schedule in a short time and is robust in performance.     

CMAC与卡尔曼滤波复合控制AVR的优化研究

电力系统的动态稳定已成为现代电力系统工程中一个关键性问题。同步发电机自动电压调节器(Automatic Voltage Regular, AVR)对于电力系统的稳定发挥着重要作用。为使AVR系统适应更加复杂的工作环境,增强AVR抵抗外界随机干扰和快速跟随输入信号的能力,提出了小脑模型神经网络、积分分离式 (Proportional Integral Differential, PID)控制器和卡尔曼滤波器复合控制的策略。通过对云南某水电厂的一台发电机AVR模型的仿真研究可知:该控制策略对于方波输入信号有很强的跟随能力,系统响应速度快,调节时间短,并且对控制通道和测量通道的干扰有很强的抑制作用。仿真结果充分验证了该控制策略的可行性,有助于电力系统的稳定。     

Robust decentralized PID-based power system stabilizer design using an ILMI approach

Thanks to its essential functionality and structure simplicity, proportional-integral-derivative (PID) controllers are commonly used by industrial utilities. A robust PID-based power system stabilizer (PSS) is proposed to properly function over a wide range of operating conditions. Uncertainties in plant parameters, due to variation in generation and load patterns, are expressed in the form of a polytopic model. The PID control problem is firstly reduced to a generalized static output feedback (SOF) synthesis. The derivative action is designed and implemented as a high-pass filter based on a low-pass block to reduce its sensitivity to sensor noise. The proposed design algorithm adopts a quadratic Lyapunov approach to guarantee α-decay rate for the entire polytope. A constrained structure of Lyapunov function and SOF gain matrix is considered to enforce a decentralized scheme. Setting of controller parameters is carried out via an iterative linear matrix inequality (ILMI). Simulation results, based on a benchmark model of a two-area four-machine test system, are presented to compare the proposed design to a well-tuned conventional PSS and to the standard IEEE-PSS4B stabilizer.     

Education for sustainability: a report card on engineering

The results of a study undertaken to determine how much engineering students learn about the way technology influences human life, society, and nature and to what extent the knowledge is used to adjust engineering methods and approaches to achieve a greater compatibility with these contexts are presented. The results suggest that the next generation of engineers is not in a good position to make a significant contribution to the development of a more sustainable way of life by substantially reducing negative impacts. The implementation of a technology policy and research strategy designed to explore the possibilities of preventive engineering that could lead to healthier social and natural ecologies, a stronger economy, more jobs, and a more sustainable way of life is discussed, and examples of such implementations are presented     

A low-cost wireless platform for first-year interdisciplinary projects

This paper presents a low-cost wireless circuit that is demonstrated to be a simple, yet flexible platform to support a variety of low-level educational activities. The circuit, implemented by many for K-12 outreach activities, is based on a 555-timer and an AM radio transmitter. At the University of Vermont, Burlington, this CricketSat circuit has enabled the development of a wide variety of wireless sensor and actuator projects. In this paper, design specifics, circuit utilization within an interdisciplinary first-year design course, and assessment results are presented. The novelty of the approach is twofold. First, the course and projects pertain to the area of wireless sensor networks. Second, student groups come up with their own project applications and problem statements for which to design a system. The key finding is that this platform has enabled students to take ownership of a concept and bring it to a working reality within the time constraints of a single semester course.     

Neural-network-based prediction of mooring forces in floatingproduction storage and offloading systems

This paper describes the development of a neural-network-based prediction of mooring forces of a deep-sea oil exploitation production process. The evolvement of a neural network simulator for analysis of the dynamic behavior of a system consisting of a turret-floating production storage and offloading (FPSO) system and a shuttle ship in tandem configuration is described. The turret-FPSO is a vessel with a cylindrical anchoring system fixed to the sea bed my mooring lines and a shuttle ship is connected during the oil transference. This system has quite complex dynamics owing to interactions of the forces and moments due to current, wind, and waves. In general, the mathematical model that represents the dynamics of these connected floating units involves a set of nonlinear equations requiring several parameters difficult to be obtained. In order to deal with such complexities, a neural network has been devised to simulate an FPSO tandem system. This approach opens new horizons for maintenance of mooring lines, preventing collisions of the ships     

Modeling the world-how it's blocked out on the Web

Placing bets on one technology over another is risky; however, there are some guiding lights. The Web is here to stay. It offers a way of sharing and presenting multimedia information to a worldwide set of interactive participants. Therefore, any technology tied to the Web's development is likely to change modeling and simulation. The tremendous interest in Java for doing simulation has taken a firm hold within the simulation field. Apart from being a good programming language, its future is intrinsically bound to the coding and interaction within a browser. VRML, and its X3D successor, represent the future of 3D immersing environments on the Web. Model handles and their accompanying object groups will remain invisible unless requested by those with a modeling bent. The modeling approach presented takes a substantial departure from existing approaches. That is the modeling environment and the object environment merge seamlessly into a single environment. There isn't a difference between a circle and a house, or a sphere and a teapot, Furthermore, objects can take on any role. This frees the modeler to choose whatever metaphor agreed upon by a certain community. There is no single syntax or structure for modeling. Modeling is both an art and a science; the realization that all objects can play roles takes us back to childhood. The Rube modeling environment is being built in the hope that by making all objects virtual we can return to free-form modeling of every kind     

Dielectric surface flashover in vacuum at 100 K

Cryogenic components in high power electrical systems and in power electronics gain more and more importance. The behavior of insulators for cryogenic conditions, however, is virtually unknown. In a fast coaxial setup, dielectric test sample and electrodes in vacuum are cooled to <100 K and flashover is characterized using fast electrical and optical diagnostics. Three consecutive development stages for flashover in self-breakdown mode with a gap distance of 0.5 cm can be distinguished: (1) a fast current rise to mA amplitudes within ~2 ns, probably associated with field emission, followed by, (2) a slow current rise to ~5 to 10 A amplitude with duration of 40 ns to 1 μs, associated with secondary emission avalanche saturation, and (3) a transition to a rapid gaseous ionization above the sample caused by electron induced outgassing, leading to impedance-limited current amplitudes of ⩽300 A. Phase (1) shows a higher final current at lower temperature, which is probably due to a higher initial velocity of the secondary electrons, the duration of phase (2) is a decreasing function of breakdown voltage and only slightly dependent on temperature, which points to a weak temperature dependence of the outgassing process. Flashover potentials show a slight increase at lower temperature     

A simulation system for craniofacial surgeries based on 3D imageprocessing

A practical simulation system based on analysis of clinical surgical procedures is described. The system provides fundamental manipulation operations to simulate actual surgical activities. There is a simulated cutting operation for sectioning a bone into various arbitrary shapes, a movement operation to transport a bone block to a desired position, and a restricted-movement operation to move a bone block until it comes into contact with other bone. The system also generates a skin surface image of a postoperative patient based on a simulated plan of bone manipulation. An operational system to enable physicians handling the system to work at ease has been devised. The structure and function of the system are described, and examples of its use in simulation are given.     

Entity-relationship modeling

The entity-relationship (ER) model and its accompanying ER diagrams are widely used for database design and systems analysis. Many books and articles just provide a definition of each modeling component and give examples of the pre-built ER diagrams. As a result, beginners in data modeling have a great deal of difficulty learning how to approach a given problem, what questions to ask in order to build a model, what rules to use while constructing an ER diagram, and why one diagram is better than another. The authors present step-by-step guidelines, a set of decision rules proven to be useful in building ER diagrams, and a case study problem with a preferred answer as well as a set of incorrect diagrams for the problem. These guidelines and decision rules have been successfully used in their beginning database management system course     

A standard model of the placement problem aimed at resolving acutting stock problem

To deal with a class of problems in which dimensions of objects to be cut are unknown beforehand, a cutting optimization technique is proposed. This solution has been applied to the wood industry. It is based on a two-level hierarchical structure consisting of a placement algorithm assigned to a given plank to optimize the cutting and a process control procedure permitting production of a requested list of pieces that is the best on a limited horizon. The placement algorithm is modeled in order to formalize the control strategy. In particular, a method for connecting a system of discrete events to the more classical theory of continuous samples systems is proposed, and under the given hypothesis, an optimal control policy is established     

Time and the eyes to see [waveform analysis]

In engineering we frequently make use of an oscilloscope to see the various forms of waves with which we work. If it is a sound wave, we would use a microphone to capture the wave. The microphone is known as a transducer, converting the acoustic energy into electrical energy. A photo-sensor acts as a transducer for a light wave and an antenna is able to retrieve a radio wave. To interpret the waves, of whichever kind, the waveform can be recorded and this is not a difficult task if the wave is displayable on the oscilloscope. Joseph Fourier (1768-1830) produced a theory that allowed us to analyze the waves that we record. His method can be likened to many of the tools that have been discussed. We have seen physical transformations to provide insights and this is a transformation of a mathematical kind.     

An efficient approach for the siting and sizing problem of distributed generation

This paper deals with the subject of finding the site and size of distributed generation in distribution systems. This problem corresponds to a mixed-integer nonlinear problem which is difficult and hard to solve with classical optimization techniques. Many approaches and with different objective functions have been applied to solve it. In this paper, the problem to solve comprises multiple distributed generation sources and the objective of minimizing power losses and generation costs, both for the distributed and conventional generators. Since it is highly combinatorial, a search space reduction is needed. So, an approximate model is used to reduce the search space of the possible buses where the distributed generation has to be located. Then, for each combination of the reduced space search, a nonlinear equations system is solved by a numerical method to get the size of the distributed generation, checking the voltage limits and the lines’ capacities. To test the method, a comparison between the proposed algorithm and a force brute algorithm is performed on a 69 and 118 bus test systems. The obtained results indicate that this method find the optimal or near optimal solution in a reasonable computation time.     

Evaluation and Enhanced Use of Light Emitting Diodes for Hydroponics

Hydroponic farming is a viable and economical farming method, which can produce safe and healthy greens and vegetables conveniently and at a relatively low cost. It is essential to provide supplemental lighting for crops grown in greenhouses to meet the daily light requirement, Daily Light Integral (DLI). The present paper investigates how effectively and efficiently LEDs can be used as a light source in hydroponics. It is important for a hydroponic grower to assess the requirement of photosynthetically active radiation (PAR) or the Photosynthetic Photon Flux Density (PPFD), in a greenhouse, and adjust the quality and quantity of supplemental lighting accordingly. A Quantum sensor (or PAR sensor) can measure PAR more accurately than a digital light meter, which measures the light intensity or illuminance in the SI unit Lux, but a PAR sensor is relatively expensive and normally not affordable by an ordinary farmer. Therefore, based on the present investigation and experimental results, a very simple way to convert light intensity measured with a Lux meter into PAR is proposed, using a simple conversion factor (41.75 according to the present work). This allows a small-scale hydroponic farmer to use a simple and inexpensive technique to assess the day to day DLI values of PAR in a greenhouse accurately using just an inexpensive light meter. The present paper also proposes a more efficient way of using LED light panels in a hydroponic system. By moving the LED light panels closer to the crop, LED light source can use a fewer number of LEDs to produce the same required daily light requirement and can increase the efficiency of the power usage to more than 80%. Specifically, the present work has determined that it is important to design more efficient vertically movable LED light panels with capabilities of switching individual LEDs on and off, for the use in greenhouses. This allows a user to control the number of LEDs that can be lit at a particular time, as required. By doing so it is possible to increase the efficiency of a LED lighting system by reducing its cost of the electricity usage.     

Practical high-impedance fault detection on distribution feeders

Distribution protection systems must balance dependability with security considerations to be practical. This is quite difficult for high-impedance faults. Only highly sensitive algorithms can achieve absolute dependability in detecting very low current faults. This high sensitivity results in a propensity for false tripping, creating a less secure, system and resulting in the potential for decreased service continuity and lower reliability. Researchers at Texas A&M University have balanced fault detection with fault discrimination, resulting in a practical combination of detection algorithms in a commercially viable system. This device has many “intelligent” features, including the ability to analyze and correlate numerous fault characteristics in real time, so that a correct determination of the status of the feeder can be made with a high probability of accuracy. This paper describes the use of multiple algorithms to detect various types of faults and the use of an expert decision maker to decipher incoming data, to determine the status and health of a distribution feeder. Requirements for a practical, secure high-impedance fault relay are also discussed. Finally, Texas A&M has licensed this technology to a commercial partner, which manufactures a device that detects high-impedance faults, in addition to performing numerous other monitoring and protection functions     

A New Control Strategy of 5-Phase PM Motor under Open-Circuited Phase Based on High Order Sliding Mode and Current References Real-Time Generation

The high quality of electrical power in high power and high reliability applications is a crucial necessity even under fault mode function. However, in these conditions, the quality of the torque is a key feature. To overcome this problem, the multiphase permanent magnet (PM) motors seems to be a very attractive choice. In order to highlight the robustness and reliability of this technology, this paper investigates the control of a five-phase PM motor under an open circuited phase fault conditions. Moreover, a High Order Sliding Mode (HOSM) controller combined to an optimal reference current generation is tested and compared to a PID controller under fault mode conditions. This original control strategy is proposed for faulted conditions. Compared to classical fault tolerant control, this strategy allows a better dynamic tracking of the non-sinusoidal reference currents and leads to a smooth torque with minimal losses even in severe fault conditions. To validate the proposed control strategy, simulation, and experimental results are presented and discussed.     

并联型有源电力滤波器设计及并网冲击电流的抑制

以LCL型三相三线制并联型有源电力滤波器为研究对象,分析和建立其在d-q坐标系下的数学模型,根据瞬时无功理论,设计了一套全数字化谐波提取及补偿算法.在推导了并网冲击电流和投入时刻关系的基础上,提出一种直流侧电压分段函数控制和装置最佳点投入电网补偿的柔性并网方案,并为确保算法能够实时运行,开发了一套基于浮点型DSP TMS320F28335和定点型DSP TMS320F2812的双CPU控制系统.经50 kVA样机实验结果验证:双CPU控制系统和全数字化补偿算法保障了装置的实时性和补偿效果,柔性并网方案有效地抑制了冲击电流.