ZnO非线性电阻在发电机灭磁中的应用

本文分析了氧化锌电阻灭磁的特点,认为这种灭磁方式比较理想。本文还研究了发电机灭磁过程中,氧化锌电阻片的特性常数和非线性系数的分散性对电阻片间能量分配的影响;得出了各种情况下能量分配的计算公式与曲线。还讨论了氧化锌电阻用于发电机灭磁的电路方案及需要进一步解决的问题。     

有关同步发电机灭磁方案的探讨（一）

对同步发电机的各种灭磁技术进行了研究，重点对各种技术方案灭磁时移能（换流）方式进行了分析，对换流能否成功进行了探讨。     

有关同步发电机灭磁方案的探讨(二)

对同步发电机的各种灭磁技术进行了研究，重点对各种技术方案灭磁时移能（换流）方式进行了分析，对换流能否成功进行了探讨。     

同步发电机灭磁保护技术方案的选择

介绍了同步发电机灭磁保护技术的发展,分析了几种灭磁保护技术方案的特点,为设计、使用单位提供了选择依据。并联移能灭磁方案提高了灭磁的快速性和过电压保护水平,电子断路器方案适用于少人值守、无人值班电站,冗余灭磁技术方案大大提高灭磁保护的可靠性。     

大型发电机组合灭磁方式

在广泛研究现有发电机灭磁方案的基础上,提出一种新型灭磁方案,即线性电阻加非线性电阻组合灭磁.仿真结果表明,该方案克服了线性灭磁速度慢的缺点,同时提高了使用纯非线性ZnO电阻灭磁的可靠性并因此减少了维护工作量.该灭磁方案已被采用到600 MW火电机组中.     

同步电机灭磁问题的探讨

本文讨论了评价灭磁效果的依据.提出了等效灭磁时间的概念和各种灭磁方式等效灭磁时间的计算方法.以具体例子比较了各种灭磁方式的效果。     

现代同步发电机灭磁系统性能综述

灭磁系统是发电机安全运行的关键环节。将国内外同步发电机灭磁系统分为3种主要类型,从各系统的灭磁原理、制造工艺、生产运行、元件性能等方面进行了论述,深入讨论了各种系统存在的优缺点,以及在各种情况下选型方案的合理性,以供新建、扩建、改造工程中进行系统选型、设备招标工作时参考。     

交流灭磁技术在发电机自并励系统中的应用

介绍几种具有代表性的灭磁保护方案 ,论述双断口磁场断路器配氧化锌非线性电阻灭磁时所需要的换流条件 ,探讨常规灭磁方案所存在的问题 ,推荐一种新型的灭磁保护方案 ,即交流灭磁 ,介绍其基本原理及试验结果 ,论述该交流灭磁方案在大型同步发电机组上应用的可行性、经济性。     

交流灭磁技术在发电机自并励系统中的应用

介绍几种具有代表性的灭磁保护方案，论述双断口磁场断路器配氧化锌非线性电阻灭磁时所需要的换流条件，探讨常规灭磁方案所存在的问题，推荐一种新型的灭磁保护方案，即交流灭磁，介绍其基本原理及试验结果，论述该交流灭磁方案在大型同步发电机组上应用的可行性、经济性。     

大型汽轮发电机的灭磁问题

归纳了交流励磁机整流励磁系统灭磁方式存在的问题。分析了大型汽轮发电机灭磁方式的特点及目前国内外对灭磁方案问题的考虑。建议采用交流励磁机灭磁作为发电机主灭磁方式。     

无刷直流电动机驱动系统的新型逆变结构

提出了简化的无刷直流电动机驱动逆变结构。新方案中，使用的功率开关管和续流二极管的数目均比传统的桥式逆变结构减少一半，并具有无直通优点。分析了两相和三相的简化逆变电路，并给出了数字仿真和样机实验结果。     

级联型多电平逆变器的功率均衡控制策略

该文针对级联型多电平逆变器的几种调制方法，包括阶梯波调制法、特定谐波消除脉宽调制法和载波空间排列SPWM法，提出了一种新的功率均衡控制策略。该策略利用级联型多电平逆变器相电压冗余的特点，通过以1/4输出周期为单位互换各个H桥单元的输出电压波形，实现了各个H桥单元在一个输出周期内的功率均衡。与现有的功率均衡策略相比，新的策略可以在一个输出周期内达到功率均衡，并具有控制简单，H桥单元功率波动小的优点，同时满足对效率和波形的要求。该文以三单元七电平级联型逆变器为例，对上述功率均衡控制策略进行了理论分析和仿真验证。     

Power flow control schemes for series-connected FACTS controllers

Unified power flow controller (UPFC) and interline power flow controller (IPFC) are FACTS devices that can control the power flow in transmission lines by injecting active and reactive voltage components in series with the lines, using power converter modules, based on an externally regulated dc-link voltage. One key issue, in this application, is to find a relationship between the injected voltage and the resulting power flow in the line. In this paper, this relationship is derived analytically, and used to design two power flow control schemes. The proposed control schemes are applicable to any series-connected FACTS controller with the capability of producing a controllable voltage. In this paper, the proposed power flow control schemes are applied to a voltage-sourced converter-based IPFC, and the resulting control performances are examined using PSCAD/EMTDC simulation package. The simulation results show the effectiveness of the proposed power flow control schemes.     

电网新设备启动方案风险评价方法

目前,对电网新设备启动方案的风险评价尚没有定量的分析方法。通过研究两种新设备启动方案中可能影响电网安全运行的各环节,用故障树分析方法,建立了新设备启动方案的故障树模型。运用概率性分析,得出两种方案的实施对电网运行的风险概率,并对风险概率进行了比较,提出了方案设计时的选择依据。实际案例证明了该方法的有效性。     

Islanding and load shedding schemes for captive power plants

This paper outlines the various schemes adopted for islanding in industrial plants with captive generation in India. Considerations in the design of islanding and load shedding schemes and reliability aspects are described. Major benefits by interfacing with SCADA are briefly given     

Control schemes for auxiliary switches of three‐phase PWM resonant snubber inverters

Control schemes for auxiliary switches of PWM controlled three‐phase resonant snubber inverters (RSIs) are proposed. The control schemes proposed in this paper are based on a conventional PWM technique. To avoid zero voltage switching lost conditions, the conventional PWM technique is modified in the proposed schemes. The proposed control schemes are so simple that they are suitable for digital control. In this paper, a CPLD (Complex Programmable Logic Device)‐based control IC, which realizes the proposed control schemes, for three‐phase auxiliary RSIs is also proposed and implemented. The IC generates gate signals for the main and auxiliary devices of the three‐phase RSI based on the proposed control schemes. The effectiveness of the proposed control schemes was verified through experiments. As a result, ZVS (Zero Voltage Switching) turn‐on at the main devices was achieved and a smooth sinusoidal output current was obtained by use of the control IC. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 152(4): 57–67, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20125     

Implementation of shielding principles for magnetic field management of power cables

Adverse health effects due to magnetic fields is a matter of great concern and has been widely debated in recent years. Managing these fields is a challenge to researchers. One of the important sources of magnetic fields is power cables. Different management techniques have been studied. In this paper, passive shielding schemes are implemented to manage the magnetic fields of power cables. The various shielding schemes can be separated into two broad categories: shielding subject and shielding source. Both schemes are implemented in this paper. Passive shielding schemes are found to be the most powerful technique as the reductions obtained are sometimes as high as 97–98%. This scheme is a costly one, should be used only in assigned locations, and as such, there has to be a trade-off between the cost and the level for reduction desired and the health desired and the health hazards.     

变速恒频风力发电机组控制技术综述

对国内外风电接入电网的输电网技术规范进行了分析和比较,明确了风电机组的控制要求及对应的控制目标.重点阐述了双馈感应异步发电机(DFIG)和多极直驱式永磁同步发电机(PMSG)2类变速恒频(VSCF)风电机组的拓扑及以最大功率点跟踪(MPPT)为目标的控制方案,其中主要对PMSG的控制方案进行了总结和比较;结合输电网技术规范对风电机组的控制要求,说明了VSCF风电机组在低电压穿越(LVRT)时的控制方案及保护措施,同样以分析PMSG的LVRT控制方案及相应保护措施为主.最后简要介绍了风电机组以提高电能质量、调频能力为目标的研究现状,并对采用分频输电技术的分频风力发电系统进行了探讨.     

Discrete-time advanced PID control systems for unknown time delay systems and their applications

PID control schemes have been used widely in most process control systems represented by chemical processes for a long time. Indeed, they are easy for most engineers in many industries to understand and for the use of various systems, whose properties are obscure. However, conventional PID control schemes have not been so available for the systems whose system parameters and time delays are unknown. The purpose of this paper is to consider advanced PID control schemes in discrete-time systems with unknown time delays. Two control schemes, that is, compound PID control systems with a local feedback compensator and a pre-compensator are proposed, and they are extended to explicit-type self-tuning PID control schemes. Furthermore, these methods are applied to a pressure-control system to show their effectiveness. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (3): 50–57, 1997     

Optimal control schemes for SSSC for dynamic series compensation

This paper presents two novel control schemes for static synchronous series compensator (SSSC) for dynamic series compensation and voltage regulation. The SSSC model comprises a harmonic neutralized multilevel 48 pulse voltage source converter. This paper investigates two novel control schemes for optimal series compensation, which are indirect control (constant reactance control) and direct control (constant voltage control) using pulse width modulation (PWM) switching techniques. The proposed model of SSSC within the power system is performed in Matlab/Simulink using the power system blockset. The performance of the SSSC schemes connected to the 230 kV grid is evaluated in both capacitive and inductive modes of operation under load excursions. The operation of the proposed controllers is also tested in a weak power in order to compare their performance for securing SSSC stability in response to system contingencies.