Blackout Prevention by Power Swing Detection and Out-of-Step Protection

Power swing evoked by sudden changes like faults or switching operations will become more and more important for protective relaying, due to the growing load flow in electrical power networks. Unwanted trips of the distance protection function must be avoided to prevent cascading effects and blackouts in the network. Selective out-of-step-tripping is required to stop unstable power swing and to prevent damage to affected generators. Therefore a reliable method for detection of power swing is presented, which requires no settings for operation. Power swing can be detected from 0.1 Hz up to 10 Hz swing frequency, also during open pole condition and during asymmetrical operation. A blocking logic prevents unselective trips by the distance protection. However, faults that occur during a power swing must be detected and cleared with a high degree of selectivity and dependability. For unstable power swing a flexible out of step tripping function will be proposed. The coordination of power swing detection, distance protection and out of step protection provides a reliable system protection.

Reciprocating Engine Step Load Response in Islanded Power Generation

The step load response of reciprocating engines is one of the key characteristics when considering its application in medium to large scale stationary power generation especially with islanded generation. This paper discusses the impacts of power frequency deviation on the generators and electrical equipment in the network and presents the relationship between step load capabilities and generator operating parameters. For a power plant consisting of a number of generators both step load and power output requirements must be satisfied. An analysis method is proposed to facilitate the development of an operation strategy which can meet both step load and power demand requirements in the full load range.? Typical reciprocating engine step load curves are used to demonstrate the analysis method and the results are further optimised for lower operational cost. This analysis method provides a general approach to operation strategy of large reciprocating engines used in islanded power generation.

Francis Turbine and Governor Improved Models Considering Step Closing Law of Guide Vanes for Power System Stability Analysis

The Francis turbine governing system models in PSD-BPA can’t precisely reflect the actual characteristics. Endeavor was done in this paper to solve the problem. An improved model of actuating mechanism was developed, which could reflect the step closing characteristic of hydro guide vanes. The effect of the inflection point value of actuating mechanism on load rejection was analyzed based on simulation. The non-linear Francis turbine model with power versus gate position module was researched in this paper. Based on field test, comparisons of simulation results with measured data were presented. The analysis demonstrates that the improved models of Francis turbine and governor proposed in this paper are more realistic than the models of BPA, and can be applied in power system simulation analysis better.

A Stoppable Clock Based Four Step Search Block-Matching Motion Estimation Architecture

Motion Estimation （ME） is considerate one of the most important compression methods. However, ME involves high computational complexity. The main goal is to reduce power conception and the execution time without reducing image quality. In this paper, the authors have proposed high parallel processing architecture is presented for four-step search block-matching motion estimation. The proposed method is based on the stoppable clock models. The architecture has been simulated and synthesized with VHDL and ASIC （CMOS 45 nm）. Synthesize results show that the proposed architecture reduces the power consumption and achieves a high performance for real time motion estimation.

Five Steps Block Predictor-Block Corrector Method for the Solution of <i>y''</i>= <i>f</i>(<i>x</i>,<i>y</i>,<i>y'</i>)

Theory has it that increasing the step length improves the accuracy of a method. In order to affirm this we increased the step length of the concept in [1] by one to get k = 5. The technique of collocation and interpolation of the power series approximate solution at some selected grid points is considered so as to generate continuous linear multistep methods with constant step sizes. Two, three and four interpolation points are considered to generate the continuous predictor-corrector methods which are implemented in block method respectively. The proposed methods when tested on some numerical examples performed more efficiently than those of [1]. Interestingly the concept of self starting [2] and that of constant order are reaffirmed in our new methods.

Analysis and Design of Single Switch Hybrid Step-Up Converter

A Single Switch Hybrid Step-up Converter with high voltage gain, which is suitable for renewable energy system, is proposed in this paper. The proposed converter consists of one switched diode-inductor cell and a capacitor. While switching, both are charged in parallel from the input source and discharged in series to the output. In order to obtain extra voltage gain at lower duty cycle, the voltage multiplier cell is integrated with the proposed converter. The main advantages of the converter are high voltage gain, reduced voltage stress, simple structure and low output voltage ripples. The operating principle and steady state theoretical analysis are presented. A 250 W prototype converter is implemented with 12 V input and 120 V output to verify the design and analysis of this converter and it has an efficiency of over 90% in all operations.

基于新型Back-stepping方法的电力系统励磁控制器设计

为了解决励磁系统的不确定性影响互联电力系统的稳定控制问题,提出一种新型的鲁棒自适应控制器递推设计方法.与传统的Back-stepping设计方法相比,新方法减少了对被控对象的严格要求,所设计的控制器避免了过度参数化和复杂化问题,能够保证闭环系统对不确定参数的自适应性以及对建模误差和有界外部干扰的鲁棒性.采用该方法设计的电力系统新型励磁控制器在华东电网上进行数值仿真,结果表明,所设计的控制器能够有效提高互联系统的暂态稳定性.

基于STEP-NC的数控车削系统的加工工艺参数优化

以STEP-NC的具体车削特征为研究对象,参照以基于STEP-NC的数控车削系统的加工工艺参数的实例,根据零件的设计要求和使用特点,综合数控车床的使用性能等数据库,分析了车床系统的优化参数和优化函数,采用软件编程开发了一种基于STEP-NC的数控车削系统的加工工艺参数优化模块。经过该模块优化后的加工工艺参数与原工艺参数相比,表明新生成的加工工艺参数使得单件加工生产成本降低、生产时间缩短、生产效益增加。

基于STEP-NC车削加工系统的关键技术

目的构建一种基于STEP-NC的数控车削加工系统,研究系统中的特征识别和程序解释两个关键技术的实现方法.方法依据STEP-NC基本理论,在VC++6.0和ST-De-veleper集成环境下,应用MFC类和STIX库、ACCESS库等进行系统的构建及程序和数据的处理.结果所构建的STEP-NC车削加工系统采用开放式的模块设计,基本功能包括自动特征识别、STEP-NC数控程序生成及程序解释等;特征识别技术采用了一种基于特征轮廓进行制造特征识别的方法;在VC++6.0环境下通过应用STIX库函数对AP238文件进行信息提取和存储实现了STEP-NC数控程序的解释.结论应用STIX库函数使程序解释过程中AP238文件数据的处理更加方便快捷;所采用特征识别方法可以较好地识别简单的旋转类车削特征.

基于STEP-NC车削仿真的关键技术探讨

基于STEP-NC的智能化数控系统开发的一部分,以车削仿真为研究对象,重点探讨了STEP-NC车削数控系统中仿真模块实现的几个关键技术,为STEP-NC车削数控系统智能化的实现提供了一定的理论依据。

基于STEP-NC车削特征的切削参数优化

文中切削参数优化数学模型以STEP-NC加工特征为建模对象,通过在系统中建立PostgreSQL切削数据库,为模型提供机床、刀具加工信息以及常用参数,利用遗传算法对数学模型进行处理从而得到优化结果。

基于OpenGL的STEP-NC车削中心加工仿真系统

为了能将STEP-NC应用到车削加工中心,开发了STEP-NC车削中心加工仿真系统。首先简要介绍了STEP-NC标准,然后对几个三维车削特征实体进行了扩充。详细叙述了车削仿真系统的工作原理,从仿真工具的选用、车削工件模型的建立和车削仿真时工件形状的实时更新等三个方面着重介绍了车削仿真系统的实现方法。最后,结合一个包含一般特征和扩充特征的实例进行了验证。实验结果表明,所提出的车削实体扩充方法是正确的,所开发的STEP-NC车削加工仿真系统是可行的。

Turned off Characteristics of Linear Ultrasonic Motor

The high controllability and high resolution control of linear ultrasonic motors depend on effective control of driving signals.For a good control characteristic,step control which the driver output turned off and on was used.Therefore,a novel dual PWM topology structure ultrasonic motor driver was designed and analyzed.According to the characteristics of the circuits,two kinds of hardware turned off methods named methods A and B were discussed.The differences of the voltage applied on motor by different methods were figured out.Finally,a series of experiments were carried out in the clean room to study the influence of step characteristic by different turn off methods.The experimental results show that the steplength was 230 nm by method A and 125 nm by method B,while cycles of driving signals were 6.The method B has a smaller steplength when cycles are 6.The average steplength varies in non-linear while driving cycles changing.The steplength varies approximately in linear while voltage amplitude changing.Therefore,method B is better to implement step control,because it gets a better control in positioning system.

Optimization Design for a High Voltage DC Power Supply Module Based on PSM Technology

Pulse step modulator （PSM） topology is applied to the EAST auxiliary heating system, which consists of a neutral beam injection （NBI） and the related microwave heating system. This paper firstly analyzes the merits and demerits of the traditional PSM modules adopted by other international companies, and then optimizes the topology of the module using the analysis results. Finally, a new topology for the PSM module （a three-phase neutral-point diode-clamped rectifier） is proposed. This new module overcomes the problems of traditional modules and has better cost-effective performance. The experimental results verify that the new module is feasible for engineering applications.

Research on Multi-Scale Modeling of Grid-Connected Distributed Photovoltaic Power Generation

The complexity of distribution network model mainly depends on the model scale of grid-connected distributed photovoltaic (PV) power generation. Therefore, the simulation performance of multi-scale PV model is the key factor of the simulation accuracy in the specific operating scenarios of distribution network. In this paper, a multi-scale model of grid connected PV distributed generation system is proposed based on the mathematical model of grid-connected distributed PV power generation. It is analyzed that differences of simulation performance, such as adaptability of simulation step size, accuracy of output and the effect on voltage profile of distribution network, between PV models with different scales in IEEE 33 node example. Simulation results indicate that the multi-scale model is effective in improving the accuracy and efficiency of simulation under different operating conditions of distribution network.

新3D STEP文件和交互模型

Power Integrations旗下子公司IGBT驱动器制造商CT-Concept Technologie GmbH布为其所有SCALETM-2 IGBT门极驱动器推出各自的3D STEP文件,以帮助设计者更快、更准确地进行新系统建模。该公司的3D交互模型包含在新的应用手册内。SCALETM-2 IGBT门极驱动器利用ASIC芯片组来减少元件数量并缩小尺寸，同时提高性能、可扩展性和可靠性。设计者使用此芯片组可优化开关的动态性能、提高整机的精度，实现灵活的设计，并缩短上市时间，应用范围涵盖150A至3600A、600V至6500V。设计工程师可以利用3DSTEP模型来确定驱动器与系统其他部分之间的机械冲突，这在机械密集度较高的设计中是特别有用的选项。

Energy Factor and Mathematical Modeling for Power DC/DC Converters

Mathematical modelling for power DC/DC converters is a historical problem accompanying DC/DC conversion technology since 1940’s. The traditional mathematical modelling is not available for complex structure converters since the differential equation order increases very high. We have to search other way to establish mathematical modelling for power DC/DC converters.We have theoretically defined a new concept-Energy Factor （EF） in this paper and researched the relations between EF and the mathematical modelling for power DC/DC converters. EF is a new concept in power DC/DC conversion technology, which thoroughly differs from the traditional concepts such as power factor （PF）, power transfer efficiency （η）, total harmonic distortion （THD） and ripple factor （RF）. EF and the subsequential EFV (and EFVD) can illustrate the system stability, reference response and interference recovery. This investigation is very helpful for system design and DC/DC converters characteristics foreseeing. Two DC/DC converters: Buck converter and Super-Lift Luo-Converter as the samples are analysed in this paper to demonstrate the applications of EF, EFV (and EFVD), PE, SE, VE （and VED）, time constant τ and damping time constant τd.

基于功率预测的自适应变步长MPPT算法研究

最大功率点跟踪技术(Maximum Power Point Tracking, MPPT)是光伏发电系统中关键技术研究的热点之一。针对传统扰动观察法跟踪速度和精度无法兼顾的问题,文中提出了一种以功率变化量为步长控制量的自适应变步长扰动观察法,通过判断功率变化趋势,对远离最大功率点,采用大步长逼近;靠近最大功率点,采用小步长逼近。建立太阳能光伏电池数学模型得到其输出特性曲线,再利用MATLAB/Simulink搭建基于Boost电路的MPPT仿真模型,最后经仿真验证了所提出算法的稳定性、快速性和准确性,它比传统算法具有更好的MPPT暂态性能。

基于组合数据清洗与NL-ConvLSTM模型的多步风电功率预测

针对风电数据在采集与传输过程中会产生大量缺失值和异常值,采用DBSCAN算法和最优组内差分法(OIV)组合筛删异常值,随机森林(RF)算法填补缺失值,提升数据准确性;并建立基于以ConvLSTM为单元的编码-预测(EF)网络的风电多气象输入多步预测模型,为了更好利用气象特征信息,在ConvLSTM模型的输入侧添加具有自注意力机制的非局部(NL)模块增强数据特征表现,从而搭建组合数据清洗方法的NL-ConvLSTM多步风电功率预测模型。实验结果表明,该方法能够进一步提高风电功率多步预测精度和稳定性。

基于信息间隙决策理论的含碳捕集−电转气综合能源系统优化调度

【目的】为科学统筹综合能源系统运行经济性、稳定性和低碳性优化目标,采用何种技术手段以提升能源转化效率,减少系统能源浪费和区域环境污染,是当下综合能源系统合理优化的主要问题。为此,提出一种基于场景生成与信息间隙决策理论的含碳捕集与封存(carbon capture and storage,CCS)—两段式电转气(power to gas,P2G)综合能源系统低碳优化策略。【方法】在技术层面,通过对电P2G两阶段精细化建模,提高氢能利用效率,建立热电联产(combined heating and power,CHP)-CCS-P2G耦合模型;在市场机制层面,引入阶梯型碳交易模型以降低系统中CO_(2)排放量。最终,基于信息间隙决策理论(IGDT)构建不同风险偏好下的优化调度模型。【结果】以典型综合能源系统进行算例分析,仿真结果表明所提模型可提高风光消纳率,实现系统低碳、经济、稳定运行。【结论】该优化策略可有效帮助决策者根据其风险偏好制定风险规避与风险追求策略下的调度方案,实现系统不确定性与经济性的平衡。