Principle of designing slope compensation in PFC Boost converter

Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction (PFC) Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensation so as to weaken or eliminate this instability. A theoretical principle on the implementation of slope compensation signal is still lacking. Empirical design will induce over compensation frequently, resulting in a large decrease of power factor. In order to tackle this issue, by constructing the discrete-time iterative map of the PFC Boost converter from the viewpoint of bifurcation control theory of nonlinear systems, consequently, the criterion of critical stability for the PFC circuit can be established. Based on this stability criterion, appropriate design of slope compensation can be achieved. Our work indicates that 3 main circuit parameters (i.e. switching cycle, output reference voltage and inductor) determine the effective amplitude design of the slope compensation signal. The results, validated by a large quantity of analytical and numerical studies, show that appropriate slope compensation can be effective in weakening (or controlling) fast-scale bifurcation while maintaining a rather high input power factor.     

Experimental verification of a dynamic voltage restorer capable of significantly reducing energy‐storage element requirements

This paper deals with a dynamic voltage restorer (DVR) characterized by installing the shunt converter at the load side. The DVR can compensate for the load voltage when a voltage sag appears in the supply voltage. An existing DVR requires a large capacitor bank or other energy‐storage elements such as double‐layer capacitors or batteries. The DVR presented in this paper requires only a small DC capacitor intended for smoothing the DC‐link voltage. Moreover, three control methods for the series converter are compared and discussed to reduce the series‐converter rating, paying attention to the zero‐sequence voltages included in the supply voltage and the compensating voltage. Experimental results obtained from a 200‐V, 5‐kW laboratory system are shown to verify the viability of the system configuration and the control methods. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 165(3): 73–82, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20460     

A Hybrid Genetic Algorithm for Selective Harmonic Elimination PWM AC/AC Converter Control

This paper presents an optimal solution for eliminating pre-specified orders of harmonics from the output waveform of AC/AC converter. The main challenge of solving the associated nonlinear equations, which are transcendental in nature and therefore have multiple solutions, is the convergence and therefore an initial point selected considerably close to the exact solution is required. The paper discusses an efficient hybrid real coded genetic algorithm (HRCGA) that reduces significantly the computational burden resulting in a fast convergence. An objective function describing a measure of effectiveness of eliminating selected orders of harmonics, while controlling the fundamental is derived and a comparison of different operating points is reported. It is observed that the modulation index can reach unity value. The theoretical findings are verified through simulation results using the PSIM software package.     

溅渣护炉技术在临钢20t转炉上的应用

介绍了转炉溅渣护炉技术在临钢20t转炉上应用的基本情况，对应用中出现的主要技术问题提出了解决措施。     

中央空调领域的节能技术

论述了我国空调耗能的现状和空调节能的意义,从中央空调系统的选择、设备选型及系统运行管理三方面分析了影响空调节能的主要因素,简述了实现节能的几个方面,并着重讨论了设计中最普遍实施的冷却水系统节能的原理和方法。     

一种新型井间地震井下数据采集系统

介绍了一种用于井间地震的新型井下数据采集系统，它以数字信号处理单片机为核心，采用新型的高精度过采样∑－△Ａ／Ｄ转换器作为采集部件，首次将数字信号处理单片机放于下，进行数据采集的控制与实时数据处理，大大生意 化了采集电路并提高了采集数据的质量。     

PLC与变频器在自动给水系统中的应用

本文介绍的是自动变频调整速恒压供水系统。着重介绍了单个变频器对多个马达对象实现自动变频的系统硬件构成、软件编制以及整个模拟调节系统的实现。     

内冷——绝热氨合成塔内件和准等温型甲醇合成塔内件技术总结

介绍了内冷－绝热氨合成塔内件和准等温型甲醇合成塔内件的技术特性、操作要点及应用情况，并对存在的问题进行了分析。     

A novel charging/discharging balancing strategy for lithium battery pack based on mixed charging mode

Series‐connected lithium batteries can be charged in the pack‐charging mode, which is most widely used in the lithium battery application field. But the pack‐charging mode will lead to cell imbalance because of the difference in the electrochemical characteristics of the cells of series‐connected batteries. On the other hand, the cell‐charging mode can avoid the imbalance problem by charging each cell independently, but it will reduce the charging efficiency and increase the cost. In this paper, a novel balancing strategy is proposed with a mixed pack‐charging and cell‐charging mode to implement the balancing algorithm. The proposed strategy aims to solve the problem of charge/discharge imbalance with the simplest balancing algorithm with high balancing performance. There is no complex balancing behaviors during the charging process – as is the case with many other existing schemes – so the control algorithm can be greatly simplified. Because each cell can be fully charged and discharged with the proposed algorithm, it helps to make full use of the energy and capacity of each cell. The system stability and reliability of the proposed system, as well as its good performance, are verified through experiments. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High‐power‐factor single‐switch AC to DC converter for LED lighting

In this paper, we report a novel single‐switch AC to DC step‐down converter suitable for light emitting diodes. The proposed topology has a buck and a buck–boost converter. The circuit is designed to operate in the discontinuous conduction mode in order to improve the power factor. In this topology, a part of the input power is connected to the load directly. This feature of the proposed topology increases the efficiency of power conversion, improves the input power factor, produces less voltage stress on intermediate stages, and reduces the output voltage in the absence of a step‐down transformer. The theoretical analysis, design procedure, and performance of the proposed converter are verified by simulation and experiment. A 36 V, 60 W prototype has been built to demonstrate the merits of this circuit. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.