Optimal operation of cascaded hydroelectric power plants in the power market

An improved network flow algorithm, which includes the minimum cost network flow and the same period network flow, is proposed to solve the optimization of cascaded hydroelectric power plants in a competitive electricity market. The typical network flow is used to find the feasible flow and add the discharge water to different cascaded hydroelectric power plants at the same step. The same period network flow is used to find the optimal flow and add the power output at a different step. This new algorithm retains the advantages of the typical network flow, such as simplicity and ease of realization. The result of the case analysis indicates that the new algorithm can achieve high calculation precision and can be used to calculate the optimal operation of cascaded hydroelectric power plants.

Study on least square modeling of heat engineering object based on typical signal response

This paper proposes a kind of least square modeling method based on typical signal response to enhance modeling accuracy of heat engineering process and adapts the environment that modeling experiment conditions are limited. The principle of this method is, under the condition of known typical pulse, step and slope signal response and model structure, to give algorithm of model parameters of identified continuous system by least square mode through derivation. The method is applied to the identification of heat exchange process for a consumer substation, and identification result obtained is compared with that of other conventional methods. After the comparison the result shows that identification accuracy is improved obviously. In addition to the good identification accuracy, this method has the characteristics such as it can identify directly continuous system model, pure lagging time, and is not sensitive to data length in the identification process. All these characteristics show that this method is simple, easy to implement and has good practicability.

Typical application of Rogowski coils in inspection of electrobath

During the aluminum electrolytic roasting process,each component of the electrobath of aluminum performs unsteadily when the electrolytic bath is in the pre-roasting stage. It is important to monitor the currents of the anodes and the cathodes of the aluminum electrobath at regular intervals. Both practice and investigation indicate that Rogowski coil can be adopted to measure heavy direct current of the anodes and the cathodes of the aluminum electrobath. The paper not only introduces the typical application of the Rogowski coil to inspect the state of aluminum electrobath in the roasting process, but also analyzes the principles of the coil sensor including its dynamic properties and some important measurement results respectively. The optimal parameters of the coil can be simulated by means of an advanced simulation tool: simulink tools based on MATLAB soft environment. Based on the gathered current data, an even-current coefficient has been introduced, and the current curve can be drawn. Since they are applied in AL-Electrolyzing, it is possible to distinguish the anode of which the current is not evenly distributed, and to take adjusting measures over a period of time to ensure that the current is evenly distributed.

Optimum line reclosing time for the enhancement of interconnected power system stability

Automatic line reclosing schemes used in an extra-high-voltage power system is an economical and effective means to maintain transient stability. A novel method is proposed in the paper to adaptively optimize the automatic line reclosing time after a transient fault for enhancement of interconnected power system transient stability. Both the study on the transient energy over network and the structure-preserving multi-machines power system model illustrate that the excessive convergence of potential energy on the lines with a certain cutset deteriorate power system stability, and therefore, an optimum line reclosing strategy can be established by minimizing the change in transient potential energy distribution across a cutset lines in the vicinity of the faulty line as an optimization target, and the optimal reclosure time is set to the time of minimum line phase angle difference. Without any pre-determined knowledge, the method is adaptive to various power system operation modes and fault conditions, and easy to implement because only a limited number of data measured at one location on a tie-line linking sub-networks are required. Simulations have been performed with the OMIB(One Machine and Infinite Bus System) and a real inter-connected power system to verify the applicability of the method proposed.

Boundary conditions: An effect of average of microscopic Maxwell’s equations

It is well known that the macroscopic Maxwell’s equations can be obtained from the corresponding microscopic or atomic equations by a proper averaging process. The purpose of this paper is to present the macroscopic Maxwell’s equations which are valid in all regions of space, including an interface between two different media; and the boundary conditions can naturally emerge from the macroscopic equations as an effect of average of the microscopic Maxwell’s equations. In addition, the application of the unit step functions and the Dirac delta function to our discussion not only permits great mathematical simplicity but also gives rise to convenient physical concepts for the description and representation of the actual fields in the vicinity of the interface.

Heating and Life Problem of High Power Density Induction Motor

An induction motor with its speed modulated by frequency features wide transfer speed range, high systematie efficiency, simple structure and long life, and it therefore becomes one of the best driving motors used in electrical vehicles. The present research trend of it is high power, high speed, high efficiency and long life. How to meet the above requirements by using the electromagnetic design, structure design and beat design, becomes a matter that needs to be resolved now. In this paper, the characters of the motor in operation are analyzed, all kinds of factors that relate to life are laid out, its heating and loss are discussed and analyzed. The key reasons affecting the motor life are presented, and different characters of a high induction motor are compared with these of a general induction motor. A design idea is described, that is : we should consider how to improve the efficiency and reliability as well as bow to reduce the heating by changing the electromagnet, structure, dissipation and operation of the motor. How to reduce its losses and to improve its dissipation has been presented in the paper.

Influence of Design Parameters on Cogging Torque in Directly Driven Permanent Magnet Synchronous Wind Generators

In order to reduce the cogging torque, this paper investigates the influence of some parameters on the cogging torque developed by directly driven permanent magnet synchronous wind generators. Based on the remanent magnetic flux densities, the cogging torque is computed by using finite element method. It is shown that many parameters have influence on cogging torque and the slot and pole number combination has a significant effect on cogging torque. A simple factor has been introduced to indicate the effect of the slot and pole number combination. Some practical experience to reduce the cogging torque was applied to 2 MW three phase permanent magnet synchronous generator at rated speed of 37.5 rpm for wind energy conversion. The simulation and experiment results verify the effect of the proposed method.

Novel sucker rod pumping system based on linear motor technology

Obtaining petroleum at the cost of electrical energy is a common problem in almost all oil fields, and it is mainly caused by low duty radio of induction motor used in beam pumping units. Traditional beam-pumping units have many intrinsic disadvantages such as low efficiency, complex transmission devices, poor flexibility, tremendous volume and weight in long stroke, etc.Therefore, a novel direct driven linear electromagnetic pumping unit (EMPU) has been developed by combining oil extraction technology with linear motor technology. The thrust of EMPU matches the changing of suspension center load to improve the system efficiency and cut down the consumption of energy. Based on previous experience, a small-scale prototype was developed and a simulation was conducted with it. Both theoretical analyses and experimental study showed that the problems exiting in beam pumping units can be solved with EMPU system, and this is a new method which can be used to solve high energy waste in oil fields.

Error analysis on heading determination via genetic algorithms

A new error analysis method is presented via genetic algorithms for high precise heading determination model based on two total positioning stations （TPSs）. The method has the ability to search all possible solution space by the genetic operators of elitist model and restriction. The result of analyzing the error of this model shows that the accuracy of this model is precise enough to meet the need of calibration for navigation systems on ship, and the search space is only 0. 03% of the total search space, and the precision of heading determination is 4＂ in a general dock.

Virtual test system for permanent-magnet DC motor

In order to obtain the primary parameters and operating characteristics of a DC motor without directly measuring its torque and rational speed, it is proposed to use a PC and a data acquisition card to acquire both the dynamic and static data of armature current to establish the performance of a DC permanent magnet motor. The accuracy and validity of this virtual test system proposed were verified by comparing the measurements made with the system proposed with the measurements made with conventional torque meters. It is concluded from the results of comparison that from the mathematic model established for the DC permant magnet motors, both major parameters and operating characteristics can be directly established for the DC motors without measuring their torques and rotational speed, a perfect on line measurement and test system has been established for the DC permanent magnet motors using the theory of virtual test system. The system proposed features shorter test time, higher efficiency and lower cost.

Transient Stability Analysis Using Transmission Line Measurement

The novel quantitative assessment method using transmission line measurement was developed. A new style of stability criterion was suggested which is based on the line measurement. The stability indices for lines, cutsets and power system according to features of transient energy in the lines were given, which not only provide a reliable and accurate assessment of the transient stability of power system, but also can be used to assess the effect of lines and cutsets on the transient stability and identify the weak transmission segment. Examples were presented by simulation on the IEEE-39 buses test system.

Torque analysis for double-stator permanent-magnet motor

In addition to the characteristics of a conventional motor, a novel direct-drive double-stator permanent-magnet brushless motor proposed can operate in the state of either a generator or a motor as appropriate. Through numerical calculation and analysis, the output torque of double-stator permanent-magnet brushless motor of the same volume as the traditional machine is discussed, and the reduction of torque ripple by using the structure features of this motor is investigated. The results indicate that lower torque ripple under the condition of ideal effective torque can be obtained by the rational design of motor. The prototype motors tested show that this kind of motor structure has a higher power density.

A new network losses allocation method in deregulated environment

Network losses allocation is one of the major problems in the market environment. The quadric function of the injected nodal power is used in this paper as a representation for network losses, which are allocated fairly using the called market equilibrium principle while the bidding curves are corrected. The power market equilibrium is simulated as three different models that can be solved simply by the optimal power flow algorithm combining the generation scheduling problem with network losses allocation. The case study is made at an IEEE-30 nodes system and a perfect result is proved in this paper.

A hybrid stepping motor system with dual CPU

An indirect method of measuring the rotor position based on the magnetic reluctance variation is presented in the paper. A single-chip microprocessor 80C196KC is utilized to compensate the phase shift produced by the process of position signals. At the same time, a DSP (Data Signal Processor) unit is used to realize the speed and current closed-loops of the hybrid stepping motor system. At last, experimental results show the control system has excellent static and dynamic characteristics.

CACER： A Novel E-commerce Recommendation Model Based on Crazy Ant Colony Algorithms

In order to deal with the problems of E-commerce online marketing, a novel E-commerce recommendation system model was given to lead consumers to efficient retrieval and consumption. And the system model was built with a crazy ant colony algorithm. Then its model, message structures and working flows were presented as following. At last, an application example and compared results were given to be analyzed. Simulation results show the model can perform better in real-time and customer satisfaction than the olds do.

Fiber Cavity Ring Down and Gain Amplification Effect

The effect of an erbium-doped fiber amplifier （EDFA） placed inside the fiber ring of a cavity ring down （CRD） configuration is studied. The limitations and advantages of this configuration are discussed, and the study of the ring-down time as a function of the current applied and gain to the EDFA is also presented. In this case, the power fluctuations in the output signal are strongly dependent on the cavity ring-down time with the EDFA gain.