Optimal Control System for UPFC

This paper first analyzes the internal dynamic process of the UPFC,then a five order differential equation is presented to describe dynamic behavior of UPFC. In term of this,a optimal control system is designed.Dynamic simulation of a transmission system demonstrates the effectiveness.     

Modelling and Analysis of Multi-terminal Unified Power Flow Controller

To control the complex powers emanating from a bus in power system, there are two solutions. The obvious solution is to equip each of the n lines radiating from the node with its own UPFC. The next evolution of the idea is to equip with a multi-terminal UPFC. First, the configuration and the principle of the Two-terminal UPFC (when n=2) are presented. In consideration of the existing shortages of output model-constructing method and topological model-constructing method for T-UPFC, a switching function mathematical model of this device is constructed by introducing the concept of switching function. It has more generality than the output and the topological model with the consideration of the internal switching character and the physical course of the T-UPFC.     

Analysis of Unified Power Flow Controller in Damping Low Frequency Oscillation of Power System

With the development and complication of power system, the problem of low frequency oscillation in electric network becomes obvious. Unified Power Flow Controller is one of the most powerful facilities in Flexible AC Transmission Systems, which can improve the transient stability and damp the low oscillation in power system with suitable control. Considering the characteristics of inverter's output voltage magnitude, adjustment of phase and process of charge and discharge of dc capacitance, the dynamic model of UPFC is proposed by a series of nonlinear differential coefficient equations. Based on UPFC's dynamic model, the linear optimal controller of UPFC with state feedback is proposed. In this way, the low frequency oscillation is damped effectively. A simulation is processed basing the theory.     

A New Heuristic Evolutionary Programming and Its Application in Solution of the Optimal Power Flow

A new algorithm,based on the combination of the evolutionary programming with the traditional gradient adjustment technique,is presented for solving the optimal power flow problem which describes some technical problems(representations of candidate solutions,evaluation function,mutation operator).Its efficiency is higher than that of general evolutionary programming.     

Distributed Power Flow Method Based on Ward Equivalent

With interconnecting and developing of power system, the problem of power flow computation on dispersed data resource need to be solved. A new distributed computation method of power flow based on Ward equivalent is presented. According to master-slaver splitting principle, multi-area interconnected power system is divided into master-slaver areas. Boundary buses in different areas are defined as different bus-types. Neighborhood areas are equivalent by Ward equivalent principle, and the equivalent injection power and equivalent impedance are worked out. Power flows from master area to slaver areas are solved by Newton method, and the equivalent injection power and equivalent impedance on the boundary are modified by their solutions. The process above repeats until to convergence. The proposed distributed power flow method takes full advantage of the information of power, voltage, network configuration in neighborhood areas, so it is better on convergence and quality of solution. The proposed algorithm is testified by IEEE 14-bus system and a practical 181-bus system.     

A Survey of Power Flow Tracing Algorithm

Competition in the electricity markets requires identifying the responsibility in the use of transmission networks or the associated effects. Power Flow Tracing algorithms have been developed recently to enhance the transparence of transmission system. This paper focuses on power flow tracing procedures and provides a detailed comparison of three classified algorithms: 1) power flow tracing based methods; 2) current tracing based methods; and 3) power flow analytic methods. The advantage and disadvantage of each method are discussed. Finally, the potential applications and development of the methodology is presented for furthermore research.     

Three Phase Harmonic Power Flow Using PhaseComponent for Asymmetric Network

With the increasement of the harmonic quantity in power system ,single phase harmonic power flow calculation can't meet the needs. This paper discusses the components model in detail under harmonic condition in three phase distribution power system, include generator,transformer,line and load. Particularly, the transformer model considers the winding connection, the phase shifting among primary and secondary windings, and the off-normal tapping.The three-phase model of transformer, used in traditional harmonic power flow, may the preuent the model from converging, so the paper proposes a three phase back forward sweep harmonic load flow algorithm based on phase-components. At last, a test example was used to prove the algorithm. The results indicate that the proposed method is efficient.     

The Multi-objective Fuzzy Optimal Power Flow Model and its Neural Network Algorithm

This paper has presented a multi-objective fuzzy optimal power flow medel.Inthe model , the multiple objectives, such as the minimum generation cost and the minimum powerloss, have been considered simultaneously, A new algorithm based on neural network models is aisopresented,in which the neural networks are employed to express, the membership function of fuzzysets and solve the optimization problems. The validity of model and algorithm is verified with numerical examples.     

Application of Evolutionary Programming in Optimal Reactive Power Dispatch

This paper describes an application of evolutionary programming(EP) to reactive power optimization and voltage control of power systems.Some technical problems which conclude mutation sacle,fitness value and population size have been solved to make EP practical for solving the optimal power flow problems.The computational results with EP have been compared with those obtained from a conventional gradient based optimization method.The comparision shows that EP are better than conventional methods in dealing with the optimization of noncontinuous and nonsmooth funcnons.The EP show the ability to search for the global optimum in reactive optimization that has multiple optima.     

Analysis of Loosely Coupled Inductive Power Transfer System

In LCIPT system, the selection of system operation frequency has a relationshi Pwith the cost and power transfer capability of the power supply. Due to the development of Power device and system efficiency requirement , it is restricted to increase the system operation frequency . This paper presentes a topology which transfers power through LC oscillation. When the voltage of the capacitor is less than reference voltage, the switch is turned off and the capacitor is charged, which makes the switching frequency far less than the syntonic frequency. Thus the system efficiency is improved, and the system cost is reduced. This is verified by the time domain and frequency domain simulations of Saber. This topology not only can be used in LCIPT, but also in other convertors.     

Analysis of Two Phase Flow Character of Test Well for Oil Extraction with Gas Lift Method

Numerical simulations are performed with RELAP5/MOD3.2 code to analyze the two-phase flow character of gas lift method in oil extraction. Gas lift startup and discharge are investigated with varying duty, and the result can provide the basis direction of oil well of simulation. code     

Analysis of Choosing the Platform in Power Geographic Information System

Geographic Information System(GIS) is playing more and more important role in information management of power system. The popular GIS platform products include GeoMedia, Arc/Info, MapInfo and MicroStation. The choosing and using of power GIS platform should obey the rule in power system reality. Based on their preponderant application in geographic industry, Arc/Info and MapInfo have been successfully used in power system. The scheme of power GIS platform is put forward in this paper, referenced to the judgement and analysis of these prevailing platform, and the example of "GIS information system in Chongqing YuBei Power Supply Bureau" is given. This example shows the powerful twice developing ability, the profound network topology analysis ability of this method, which could also satisfy the needs of excessive and separate work nodes and parallel operation. All researches showed in this paper demonstrate the method could satisfy the need of power GIS.     

An Improved Method of the Transient Waveform Analysis in Power Systems

The angular frequency and decaying constant of each copmonect for the transient waveform in power systems were obtained by using the discrete Fourier transform; the amplitude and phase angle were calculated in the linear curve fitting method. And all of the parameters obtained above were treated in an unified optimization by using the curve fitting optimization of the least square method of general nonlinear funcrion so as to get the results of waveform analysis. Two examples are included.     

马铃薯太阳能风补发电控温土窖的设计及效果分析

为开发低投入、低能耗的马铃薯贮藏库,通过设计、性能测试和贮藏试验,研制出太阳能风补发电控温土窖。该土窖库体结构简单,施工方便,总热阻大于2.84 m~2·℃/W,比普通冷库能耗减少90%。马铃薯贮藏120 d后,好薯率为97.6%,硬度为63.16 kg/cm~2,其他指标均优于传统土窖。太阳能风补发电控温土窖具有利用自然冷源、机械制冷、保温控温的功能,适合马铃薯的长期贮藏。     

A New Algorithm for Open Conductor Faults in Power Systems with Variable Structures

A new method to calculate electric values of unsymmetrical open conductorfaults in power systems with variable structures and parameters is proposed. All the fault componentsof nodal voltage or branch current and the equivalent parameters of open port for each sequence net-work can be obtained rapidly. The method presented here is much more understandable in contrast tothose available, and meanwhile the amount of calculations is greatly reduced. Its effectiveness hasbeen verified by numerical examples.     

Hybrid Electric Vehicle and Its Electrical Drive System

Hybrid electric vehicle (HEV) is a mixture of electric vehicle and conventional vehicle, which has the merits of reducing exhaust gas and the consumption of gasoline HEV is the new development way of automobile industry. This paper introduces HEV, and discusses the essential framework of HEV drive system,the basic types of the electrical drive and their features and the present state of the development at home and abroad.Some key technologies are also proposed which determine the drive and control performance of HEV.     

Constant Flow Hydraulic System to Variable System for Energy efficiency

This paper analyzed the feasibility of convert the constant flow hydraulic system to variable system in order to realize the regulating of the water flow rate in central air conditioning.The detailed design scheme,which uses transducer and industrial cornputer to implement the hydraulic system energy efficiency controlling for this projiect,is illustrated.The hardware system which uses transducer and computer is connected by RS-485.Software partially uses Visual(C++6.0) to compile the entire procedure.Result of the project proves the energy-saving effect of this control system.     

Novel Single-phase Series Active Power Filter with Power Equilibrium

Grounded on the theory of power equilibrium, a novel single phase series active power filter (APF) is proposed . By analyzing the power equilibrium character of series APF, the control algorithm and equation are deduced. In the proposed control strategy, instead of the fundamental current detection and complex computation, only the capacitance voltage and the source current on d.c. side are needed. The clear control loop has been realized with simple circuit and the series proposed APF can compensate both reactive and harmonic current simultaneously. The simulation results show the excellent compensation effect and confirm the validity of theoretical analysis.     

A Spot Price Model with Var Cost

This paper has applied the var cost to the theory of spot price.An augmented Lagrange method is employed to develop the exact model of spot price of active power and reactive power,and the physical means of Lagrange multipliers are explained.The numerical examples are given to demonstrate the validity of the proposed model.