Dielectric measurements for power electronic applications

Capacitors are utilized in a variety of different ways in power electronic circuits. Typical applications are in snubber, clamping, and resonant circuits. For design purposes, it is necessary to make an accurate measurement of the actual behavior of the capacitance that is added to the circuit under conditions related to those prevailing in a converter. For this purpose, a number of different measurement systems or techniques can be utilized. Four of these measurement systems are compared. These are small-signal variable-frequency measurement, large-signal quasi-DC measurement, in-situ high-voltage measurement and small-signal with large DC bias voltage measurement. Each of these measurement techniques returns characteristic values based on its particular model of the test capacitor. These tests are done on both ceramic and nonceramic capacitors at room temperature. The results are discussed     

A comparative evaluation of harmonic reduction techniques inthree-phase utility interface of power electronic loads

Power electronic loads inject harmonic currents into the utility system. This paper presents a comparative evaluation of harmonic reduction techniques which satisfy the current harmonic limits specified by the IEEE Standard 519, and at the same time provide a regulated DC output voltage. The techniques considered include active and hybrid filters, and various current waveshaping approaches for a three-phase utility interface. These techniques are compared in terms of their complexity (number of switches) and their component ratings. Based on the application requirements and the cost of active and passive components, this paper enables the estimation of the minimum cost topology     

A new methodology for probabilistic short-circuit evaluation with applications in power quality analysis

The main aim of this paper is to propose a probabilistic short-circuit approach to generate the probability distributions of the System Average RMS Variation Index (SARFI) index. The proposed methodology is based on the combination of the admittance summation method in phase coordinates with the Monte Carlo method. This new approach has been tested in a feeder belonging to an electricity distribution company in the Northeast of Brazil to generate the probability distributions of the SARFI index. The tests results demonstrated that the proposed model is a powerful tool to stochastic prediction of voltage sags.     

A new public-domain simulator for power electronic circuits

A new public-domain simulator (SEQUEL) for power electronic circuits is described. The organization of the simulator is briefly discussed. The most important feature of the simulator is that the user can define new elements in a flexible manner. The differences between the new simulator and other simulators are enumerated. Some simulation examples are discussed to demonstrate the applications of the simulator. It is pointed out that the new simulator is particularly attractive for engineering institutes in developing countries where access to expensive commercial packages with similar capabilities may be difficult     

Supercapacitors and lithium-ion batteries for power electronic applications

This article employs the method of electrochemical impedance spectroscopy (EIS) to extend the physics-based, nonlinear equivalent circuit models of supercapacitors (SCs) to describe lithium-ion batteries (Li-ion). The following section briefly introduces the method of electrochemical impedance spectroscopy and presents measured impedance spectra. From these spectra, appropriate equivalent-circuit models are deduced. After this, the MATLAB/Simulink implementation of the new simulation models is discussed, and simulation results, as well as verification measurements, are provided. Finally, conclusions are drawn, and future perspectives of the new impedance-based modeling approach are outlined.     

Low temperature cofirable MnZn ferrite for power electronic applications

A new MnZn ferrite tape material for sintering at 900 °C and its performance in power electronic embedded multilayer inductors of several μH inductance are described. The low sintering temperature is achieved by optimizing powder processing and sintering additives. The material is suited for processing within the low temperature cofired ceramics (LTCC) technology and it is particularly compatible with low loss Ag metallization. Although reduced by a factor of two compared to high-temperature sintered material, its relative amplitude permeability of 700 allows for numerous device applications below the Curie temperature of 260 °C. Volumetric losses are not affected by the new material formulation since increased hysteresis losses are compensated by reduced eddy current losses. Power line filters with ceramic integrated inductors and surface mounted capacitors exhibit a current capacity of up to 10 A and a shift in cutoff frequency compatible with the measured B–H curve of the material. By integration of these inductors with conventional dielectric LTCC tapes a strain-induced permeability quenching is revealed and attributed to magnetostriction. Therefore good thermal matching between tape materials is needed, but the effect also permits construction of variometers and pressure sensors without moving mechanical parts.     

一种描述电力电子电路状态转换的新方法

在开发采用集成芯片控制的电力电子系统时,电力电子电路研究人员与嵌入式软件编制人员之间缺乏简单有效的沟通方法.通过对电力电子电路特点的分析,得到相对于控制器出口"可见"部分电路状态集的组成形式.定义了扩展有限状态机EFSM(Extended Finite State Machine)模型,提出基于EFSM的电力电子电路状态转化的描述方法.以带饱和电感的移相式软PWM逆变电路为实例,用EFSM模型进行了描述.实例模型体现了电路状态之间转换的连续直观和系统的完整性.此方法简洁有效.     

Impedance-based simulation models of supercapacitors and Li-ion batteries for power electronic applications

To predict performance of modern power electronic systems, simulation-based design methods are used. This work employs the method of electrochemical impedance spectroscopy to find new equivalent-circuit models for supercapacitors and Lithium-ion batteries.     

风电社会效益的评价模型及其应用研究

给出风电社会效益的定义,其内容包括电能服务效益、容量服务效益和环境效益.从局部均衡福利分析角度,建立了风电社会效益的概率型的数学模型,该模型能保守估算风电的社会效益,并运用此模型进行实证研究,结果表明模型具有可用性.     

Technologies and applications of Al‐free high‐power laser diodes

We report high‐power technologies in 0.8‐µm Al‐free InGaAsP/InGaP laser diodes. To realize the high‐power operation, the improvement of catastrophic optical mirror damage (COMD) power density level is required. In addition to the use of low surface recombination velocity of Al‐free materials, optimization of waveguide thickness in broad waveguide structure with tensile‐strained barriers and current blocking structure near facets has led to high COMD power density level. Highly stable operation of Al‐free laser diodes with these structures has been obtained over 2500 hours at 2 W from a stripe width of µm. Applications of high‐power laser diodes are also described. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(1): 53–59, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20286     

Virtual synchronous machine-controlled grid-connected power electronic converter as a ROCOF control device for power system applications

Electrical Engineering - Rate of change of frequency (ROCOF) is an indicator of frequency stability of a power system network. Maintaining the ROCOF value within the acceptable limit is a major...     

Simplified models of a single-phase power electronic inverter for railway power system stability analysis—Development and evaluation

Use of power electronic equipment has increased and introduced new dynamical phenomena in power systems. For example, new electric rail vehicles (locomotives) equipped with modern power electronic traction chains have caused situations of low-frequency power oscillations and instability in single-phase railway power supply systems. This paper presents the development and implementation of an instantaneous value model and simplified fundamental frequency (RMS) models of such an advanced electric rail vehicle in order to investigate their representation of low-frequency dynamics. The dynamical behaviour is studied by use of both time-domain simulations and linear analysis (eigenvalues) and the degree of simplifications regarding controller dynamics and power system dynamics are presented and discussed. An enhanced RMS model is tested in order to account for the impact of fast current dynamics on the low-frequency behaviour. The results show that this enhanced model is corresponding more closely to the instantaneous value model than what can be obtained by the traditional RMS simplifications and indicate that current dynamics should be included in stability studies involving power electronic inverters.     

A new method for evaluation of the load transfer capability of trunk power networks

Today, a more effective power network is a key solution to the right‐of‐way problem in terms of transmission cost reduction. Various advanced techniques and planning methods are currently adopted in power utilities for this purpose. So far, the authors have presented two approaches for the rational coordination of transfer capability with transmission reliability. One is a method for numerical evaluation of the increase in critical transferable power resulting from lightning countermeasures on a long transmission route. The other is an index of the system margin to be uniformly allocated in a power system from the adequacy point of view. This paper proposes a new concept of system margin from the dynamic stability point of view and a new definition of probabilistic load transfer capability, both aiming for quantitative evaluation of power system alternative plans. Several different fault patterns have been taken into account, with their associated occurrence frequency and critical transferable power. These proposals are applicable to the practices of power utilities in conjunction with the conventional planning methods. This paper also illustrates numerical examples of the proposed methods as applied to a 500‐kV trunk model power system. © 1999 Scripta Technica, Electr Eng Jpn, 128(1): 17–25, 1999     

新型电力系统下电能质量信号的分数域降噪方法研究

“双碳”背景下,大量分布式电源接入电网引发电能质量扰动,给电网的稳定运行带来挑战。由于非线性、高速负载的大量集成,新型电力系统中的电能质量扰动呈现出非平稳特性,给降噪处理带来了新困难。针对这一问题,通过分析不同类型电能质量扰动在分数域的能量分布特性,提出了一种改进的基于分数阶傅里叶变换(FRFT)的降噪算法。同时,文章对分数阶最佳变换角度的估计方法进行了讨论,基于信号的分数阶频谱四阶原点矩,利用一维峰值搜索确定最佳变换角度可有效降低计算复杂度。实验结果表明,改进算法对平稳暂态扰动和非平稳暂态扰动均能有效实现降噪并保留暂态扰动的定位信息。     

A signal processing module for power system applications

This paper presents a unified power signal processor (PSP) for use in various applications in power systems. The introduced PSP is capable of providing a large number of signals and pieces of information which are frequently required for control, protection, status evaluation, and power quality monitoring of power systems. The PSP receives a set of locally measured three-phase voltage and current signals and provides their fundamental components, amplitudes, phase angles, frequency, harmonics, instantaneous and stationary symmetrical components, active and reactive currents and powers, power factor, and the total harmonic distortion. Simplicity and integrity of its structure as well as its robustness with respect to internal parameters and external disturbances and noise render the proposed scheme very attractive for practical implementations.     

多端口级联式电力电子变压器可靠性评估模型及其应用

多端口级联式电力电子变压器(Power Electronic Transformer, PET)是未来实现多电压等级、交直流混联形态配电网的核心设备,其可靠性对于配电网可靠性水平影响较大。首先分析了多端口级联式PET典型拓扑结构及工作原理。其次基于工程可靠性原理研究建立了考虑器件冗余的PET可靠性评估模型。然后分析了PET对交直流混合配电网可靠性的影响。最后针对某"手拉手"结构交直流混合配电网进行算例分析。计算了PET不同设计模式、冗余度下的可靠性水平。进行了PET对交直流混合配电系统可靠性的影响及其灵敏度分析,验证了所提算法的正确性和有效性。     

Experimental performance evaluation of a wavelet-based on-linevoltage detection method for power quality applications

This paper evaluates the performance of a wavelet-based, online (real-time) voltage detection scheme for power quality applications. The objectives are: (1) to demonstrate suitability of the proposed method in detecting faults/disturbances in a power system; and (2) to compare its performance with that of a conventional scheme. Two (STS) systems are chosen as frameworks for comparison; a low-voltage laboratory STS setup for which measured results are provided, and a medium-voltage STS system for which detection times are derived based on simulation, using the EMTDC/PSCAD     

A distortion-free phase-locked loop system for FACTS and power electronic controllers

This paper presents a single-phase phase-locked loop (PLL) system which is primarily free from the double-frequency ripples from which the conventional PLL system suffers. The proposed PLL is then extended to reject the harmonic components from the input signal and to estimate the phase-angle and frequency of the distorted input signal with no error. Three units of the proposed PLL can be used in three-phase power systems, such as FACTS and HVDC converters, to estimate the phase-angles of the individual phases with no double-frequency ripples and without sensitivity to the presence of harmonics and inter-harmonics. This makes the proposed PLL unique and desirable for applications which demand highly accurate estimation of the phase-angle(s) and frequency.     

基于碳化硅电源的双芯智能电能表的可靠性测试研究

基于碳化硅电源的双芯智能电能表是新技术在工程领域特别是电力行业的重要尝试。针对其缺少可靠性检测标准的问题,文中根据现有智能电能表运行环境,同时结合碳化硅开关电源和双芯智能电能表特点,通过对电能表各项应力分析,提出了其可靠性检测方案及相应具体方法。提出的检测方案对于确定基于碳化硅开关电源的双芯智能电能表整机的可靠性指标具有十分重要的指导意义,从而实现提升智能电网技术水平,保障电网安全稳定运行的目的。     

新型半无机硅钢片漆的研制

为提高大电机的运行可靠性,研制了一种新型半无机硅钢片漆,试验结果表明,该漆不仅符合通用硅钢片漆的基本要求,而且经Franklin烧损试验,在150±5℃/5.2MPa/0.5V(DC)条件下测得的泄漏电流平均值不大于0.2A,使铁芯在过热状态下仍能保持良好的绝缘性能。