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.     

A New Method of Piece-Wise Solution in Faulted Power Systems with Variable Configurations

A new model and its algorithm are presented in this paper to simulate calculating the electric values of short circuit fault in large-scale power systems with variable configurations. The method proposed herein reduces the computer storage requirements compared with the available approaches. And it completely avoids the modification computation of nodal impedance (or admittance) matrices of the original networks and the repeated calculations for each type of faults.     

Approach for Calculating Short Circuit on Transrmission Lines by Using Piece-wise Method with Structure Network Fault

Based on the properties of linear network,a new generalized diakoptical modeland its algorithm are presented in the paper to calculate short circuit at the arbitrary location on anytransmission line of large-scale power systems,in which the proposed techniques of transferring faultport current,and modifying nodal current sources and column impedence elements, are appliedcomprekensively. The method given here is espocially efficient to calculate short circuit in piece-wisemethod for any mutually coupled cuts between subdivisions in the system with constant or variablestructures. And it is an important improvement for short-circuit current calculation.     

Calculation of lumped parameter of two-port network forvolume conduction energy transfer

Skin electrode unit is a channel through which energy can be transferred to the implanted device by volume conduction. The unit can be equivalent to lumped circuit, but so far there are no appropriate calculation methods of these circuit parameters, so variable load method based on field-circuit coupled is proposed. A skin electrode unit field circuit coupled model is established to obtain the relationship of the network parameters between voltage and current at electrode port, and the amplitude and phase of the power signal is extracted by the use of all phase FFT spectrum analysis. On this basis, equivalent circuit impedance parameters of the skin electrode unit under various conditions are obtained by the application of variable load method and the validity of the method is verified. As a result, the equivalent circuit impedance parameters obtained in this way can be used for the circuit analysis and optimization of the volume conduction energy transfer system.     

The Calculation of Transient Overvoltages on the Signal Cable Conductors Ocurring Equipment Faulting in Power System

This thesis studies circuit model for calculating transient overvoltages on the signal cable conduuctors,and the computational method and program of cable parameters.The transient overvoltages on the signal cable conductors ocurring equipment faulting in a 500 kV power system is calculated by EMTP.     

One-cycle Control Three-phase Four-wire Active Power Filter with Four-arm

This paper presents a three-phase four - wire active power filter based on one-cycle control. This method need not sense the three phase load currents or the three phase voltages, need not use any multipliers. It has simplified circuit , and the controller is composed of four integrators with reset along with several flip-flops, comparators and some analog components. The main circuit switching frequency is constant, which is desirable for industrial applications. Analysis and simulation are carried out with the four-arm inverter, the simulation results verify that the APF with one-cycle control can dynamically and effectually compensate the harmonics, reactive current and zero sequence current.     

Dual channel transmission method based on LSK and PSKfor passive setting system

For separate transmission of received data and current fuze status data in a paasive setting system, a dual channel transmission method based on LSK and PSK is proposed. The corresponding feedback transmission model is set up. The methods for circuit realization and circuit parameters selection are also presented. This method has the advantage of easy circuit realization, low energy consumption, and quick and reliable information feedback. The test shows it can realize the stable dual feedback of 6.25 kbps setting data and 50 kbps status data of fuze in the same wireless channel when the DC voltage is not lower than 3 V. The design and modulation of principal prototype have been completed.     

矿用高压开关电器短路开断与关合试验电源

针对国内冲击发电机性能参数不足,以国外冲击发电机作为试验电源,建立基于直接试验法的矿用高压开关电器短路开断与关合试验系统,提出了一种新的技术解决方案。仿真试验结果表明,该方案满足综合性煤矿高压电气实验室建设项目技术指标和试验标准要求,为大容量开断与关合试验系统设计和建造提供一种技术思路。     

Parameter design and simulation for animproved direct current side active power filter

Considering the characteristics of the dc side series active power filter (APF) that the output voltage cannot be adjusted and the control circuit is complex , an improved single phase dc series APF topology is proposed. The improvement of the new circuit topology and fundamental working principle are analyzed. Following the circuit power factor pre regulator principle, the designing method for the main circuit parameters is given. The voltage ring and the current ring are designed by using the zero pole method. The main circuit power switch is controlled with the same frequencies, while the control circuit was simplified further. Compared with the paralleled APF, the main circuit of topology structure is simplified and the number of the active switches is reduced, which show low input current harmonics, high power factor, large voltage output adjustment range and low cost. The simulation results prove that the proposed topology is correct and reliable.     

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.     

电液驱动式变量施肥闭环控制系统研究

变量施肥技术是精准农业技术的重要组成部分。由于施肥机是通过液压马达驱动的,本文设计相应驱动方式下的基于单片机的控制器。该控制器通过串口RS232接收来自田间计算机的控制命令,进行解析处理后,生成相应的I/O口信号,经过驱动电路放大后控制执行元件动作。同时,控制器利用车速度传感器、排肥轴磁阻转速传感器通过采样获得排肥轴转速信息,反馈给控制器实现闭环控制。变量施肥试验表明,所设计的变量施肥控制器能满足变量作业的要求。     

Fast modeling of the motor broadband equivalent circuit model

This paper proposes a modeling method of the motor broadband equivalent circuit model. The impedance amplitude-frequency characteristics of the motor terminal through measuring are obtained. The impedance amplitude-frequency characteristics are devided into several regions based on its first resonant point information,and the motor broadband circuit topology is developed with each region equaling a resonance unit. The RLC parameters of resonance unit are extracted through frequency and corresponding impedance of the any non-resonant and resonant point in each unit. This proposed method is used to build DC and AC motor broadband equivalent circuit model. Their impedance amplitude-frequency characteristics are simulated by the Saber software. The measurement results and the simulation result of references are compared. The DC motor simulation results coincide with the measurement results in 0.1~50 MHz,and the AC motor is in 0.1~40 MHz. The results show that the motor broadband circuit model is reliable and feasible.     

The power-supply of X-ray machine adopting PID control and high-frequency inverter technology

To solve the problem of low control accuracy and low stability of current X-ray machines, a kind of digital power supply for X-ray machine is introduced. In the digital power supply, some key technologies are used to improve the output stability of the high frequency inverter, including improved BUCK circuit for voltage regulating circuit, high frequency inverter and soft switching technology for the high-voltage generator. The PWM control technology is used to control the switch transistor of voltage regulating circuit and inverter circuit, which makes the drive waveform output stable and easy to control. In order to improve the control accuracy, reduce the volume and change high voltage consecutively, the software PID of the microcomputer is used to control the feedback circuit. The high-accuracy power chip is used for the filament power supply to make the filament electric current stable. Through the analysis of the circuit, the parameters of the circuit are calculated and the circuit is simulated by PSPICE software. The results show that the theoretical analysis is consistent with the practical simulation results. The design can meet the requirement of the technology indices of the power supply of the X-ray machines.     

Selection of Hot Water Circulating Pump Related Parameters

In multistoried or the high-rise civil constructions the full-time machinery hot water circulation supply system design,whether the design parameters for the flow and the lift of circulating pump are appropriate or not,will be related to continuously,safe,stably running of the hot water supply system.This paper introduces parameter selections of hot water circulating pump both at home and abroad.Based on the difference of these selection means it analyzes the calculating means of the flow and the lift of circulating pump.Whether the circulator flow should join the additional circulating flow or not is the focal point in the argument.In China's present "Code for design of building water supply and drainage" the additional circulating flow is considered not flowing through the circulating pump,so in calculation the additional circulating flow does not contain the circulator flow.By analysis of the water distribution operating mode and various ring circuits difference,as well as considering that for the very small circulator flow it is more difficult to use the valve regulation and to achieve balance between various ring circuits resistance loss,inaccessible absolute circulation in the same regulation,short circuit and so on,the circulator flow should be the sum of circulating flow and additional circulating flow.To calculate lift head the additional circulating flow should be considered through the calculating loop.     

Full bridge LLC series resonant converter for X-Ray high voltage DC power supply

To prevent the duty cycle loss of full-bridge converter controlled by the phase-shifting method, a high frequency high voltage X-ray power supply is proposed. It combines full bridge LLC(FB-LLC) series resonant converter with bipolar single-phase symmetrical voltage multiplier. FB-LLC series resonant, high voltage transformer and bipolar single-phase symmetrical voltage multiplier are used in the main circuit. The LLC series resonant circuit and working conditions of soft switch are analyzed. The fundamental harmonic approximation model is established. The parameters of the main circuit are designed. The simulation results show that the output voltage adjusted continuously within 40~120 kV and without duty cycle loss. The X-ray power supply is proposed to achieve a quick rise and low ripple of output voltage. According to the simulation results, the proposed topology is correct and reliable.     

A Digital Thyristor Trigger Control System of Three Phase Full-control-bridge on the Base of Singlechip Controller

A new type of digital trigger control system on the base of Singlechip Controller is proposed for water power station control system. The trigger use the singlechip controller's highspeed output port skillfully, and this system included controller and trigger,so as to reduce the component, reduce the cost and make the system more integrated, more precise and more reliable and advanced the hydro excitation control system. In this system, we use new electric technology, new detection technology and new automatic theory, so as to make the system more perfect and more intelligent. It has overcome the disadvantage of simulation integrate circuit in above.     

同步发电机励磁绕组匝间短路故障在线分析方法综述

励磁绕组匝间短路是同步发电机常见故障之一。为保证机组和电网的安全可靠运行,有必要对该故障进行在线分析检测。首先介绍了应用于同步发电机励磁绕组匝间短路故障在线分析的磁场-电流谐波分析法、探测线圈法、多回路法、输出电气量分析法、振动分析法等的研究现状,并对几种方法进行了比较,然后对未来在线分析方法的发展方向进行了展望,对输出电气量分析法提出了两条研究思路,最后说明了在线分析方法应具有实际可行性和多用途性。     

Optimization of Helix Intake Port Based on Numerical Simulation

With numerical simulation, an analysis is done on the three-dimension air flow in the helix intake port of a diesel engine. The anthors acquire the distribution of characteristic parameters of air in the port, such as velocity, pressure, turbulence kinetic energy, as well as the flow coefficient and rotate moment around the erect axes at the outlet. The results of simulation indicate that the negotiability of the port is very good while the ability of forming eddy can be enhanced, so several improve measures have been put forward. Comparing with simulation results of these measures, it finds out that the method of combining increase the distance between the definition curve of volute cavity and central line of valve protruding support as well as increase the eddy shell angle can obviously enhance the ability of forming eddy, which is an efficient and rational method.     

Multi-field coupled numerical simulation of volume conduction energy transfer

The research on volume conductive model can be used in designing the conductive systems and optimizing the energy transfer parameters. By considering the coupling of circuit, electromagnetic-field and temperature-field, a 3-D multi-filed coupling model is developed. On the circuit level, the simulation of volume conduction, real-time monitoring for the temperature of skin tissue are achieved, which provides direct theoretical guidance for energy transfer optimization design. With the software FEM 3.5, a volume conduct multi-field coupling model is built to verify the feasibility of volume conduction, which also lays foundation for further optimize energy transfer efficiency.