An overheating‐tolerant space vector modulation algorithm for multilevel inverters

As promising and suitable candidates for high‐power applications, multilevel inverters have become one of the most promising solutions in various applications. However, power switching devices are highly subjected to thermal overheating, which leads to shortened lifetime and reduced reliability. Thermal overheating may result from the degradation of power switching devices due to continuous overloading and power cycling. In addition, degradation and faults in the cooling system of power switching devices may cause thermal stresses as well. A new overheating‐tolerant space vector modulation algorithm is proposed in this paper to alleviate thermal stresses from overheated power switching device. The proposed algorithm relies on using the redundancy property between switching states in multilevel inverters to continuously evaluate a cost function of the junction temperature of the overheated device for all possible switching sequence sets and then selects the optimal switching sequence. In addition, the proposed algorithm preserves the DC‐link capacitor voltage without reduction in the output current of the inverter. The proposed algorithm is general, which can be applied to n‐level inverters. Both simulation and experimental results reveal the efficient performance of the proposed algorithm using a three‐level T‐type inverter as a case study. Accordingly, the lifetime and reliability of the inverter are enhanced considerably using the proposed algorithm. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Commander SK变频驱动器在摆频控制中的应用

根据纺织摆频的特性,结合CT公司的Commander SK变频器所具备的独特的功能,对Commander SK变频驱动器在纺织摆频控制上的应用进行了研究,并找到一种简单可靠的摆频控制解决方案。     

浅谈给粉机变频调速

变频调速可靠性高,调速性能优越,随着变频器价格的下降,给粉机使用变频器调速已经成为可能。下面就结合车间三台锅炉24台给粉机的实际情况谈一下笔者对变频给粉机的认识。     

新型载波移相同步脉冲发生器的研究

提出一种新型载波移相同步脉冲发生器。该发生器基于工业以太网分布时钟,可以产生纳秒级的高精度同步脉冲信号,信号用来同步链式多电平逆变器所有阀体输出的PWM脉冲。该控制系统成功应用于10 k V/1 Mvar级静止同步补偿器（STATCOM）装置。     

Seamless Transfer Control Strategy for Grid-Interactive Inverters

Abstract—Single-phase microgrids are widely used in residential houses. The energy storage system with grid-interactive inverters in these microgrids should operate in both grid-tied and standalone modes. In this article, proportional resonant controller for the single-phase grid-interactive inverter with LCL-filter is designed and implimented in the both operation modes. Also, a novel seamless transfer strategy based on hysteresis current control is proposed when off-grid transfer operation is needed. With the proposed method, the inverter is able to provide voltage support to the local critical loads during the whole transfer process when the grid fails. For the grid-tied transfer process, a phase difference eliminating method based on inverter frequency regulation is introduced in this article to eliminate the phase difference between the grid voltage and the inverter voltage when the grid recovers. Simulation and experiments are carried out and the results verify the effectiveness of the proposed control method.     

圆盘剪机列电气控制系统的改造

介绍PLC、直流全数字调速装置及交流变频调速器在钛板圆盘剪机列电控系统上的应用。     

Offshore wind farm with a series multiterminal CSI HVDC

This paper presents an integrated design of an offshore wind farm and an interconnection circuit based on a series multiterminal HVDC link with current source inverters (CSI). The transmission converters are used to achieve variable speed operation for a group of generators, and this enables use of very simple generators. The series converter connection eliminates offshore transformers. The paper discusses the control systems for both, generator side and grid side converters. A 200 MW wind farm is simulated on PSCAD/EMTDC platform and the responses confirm satisfactory operation for a range of wind speed changes. It is shown that each generator group can operate with a different and optimal frequency and that wind variations on individual units cannot jeopardize system stability. The main challenges for the proposed topology are system insulation and management of transmission line losses, and the paper studies some possible solutions.     

Cascaded Multilevel Inverters Using Proposed Series Sub-multilevel Basic Blocks with Reduced Switching Devices

In this paper, a novel configuration of the cascaded multilevel inverters using series connection of new sub-multilevel basic blocks is presented. The basic structure of the proposed sub-multilevel inverter is made of three isolated batteries and eight unidirectional power switches. Hereby, by changing the polarity of one of such batteries and two power switches, two different modules of sub-multilevel inverters can be extracted that each of them is able to be incorporated into two different cascaded structures as the series basic blocks. Contemporary, to determine the suitable magnitudes of the integrated batteries, two different algorithms for each topology along with their relevant mathematical analysis have been also given. In this study, a complete comparison between the proposed topologies and several recently presented structures has been conducted. The compiled comparisons can prove the fact that both the proposed cascaded inverters are capable of generating a higher number of output voltage levels with less number of switching counts. Other advantages of these structures are reduction of voltage sources numbers, DC sources variety, value of total blocking voltage, and also conducting losses. In order to demonstrate the correct operation of the proposed structures and presented algorithms, some experimental results will be also shown.     

光伏并网多个逆变器并联运行控制及实现

传统的逆变器并联控制方案中各个模块相互之间存在连线.随着模块数目的增加和模块间距离的增大,各个模块之间的信号容易受到干扰.根据逆变器并联运行的原理,该文分析了几种逆变器并联的控制方案,比较了几种常见的PQ下垂法的优缺点,进一步研究了无互联线逆变器并联控制策略,介绍了一种更加适合光伏并网系统的无互联线逆变器并联控制方案,...     

Solution‐Processed Small‐Molecule Bulk Heterojunction Ambipolar Transistors

Solution‐processed small‐molecule bulk heterojunction (BHJ) ambipolar organic thin‐film transistors are fabricated based on a combination of [2‐phenylbenzo[d,d']thieno[3,2‐b;4,5‐b']dithiophene (P‐BTDT) : 2‐(4‐n‐octylphenyl)benzo[d,d ']thieno[3,2‐b;4,5‐b']dithiophene (OP‐BTDT)] and C₆₀. Treating high electrical performance vacuum‐deposited P‐BTDT organic semiconductors with a newly developed solution‐processed organic semiconductor material, OP‐BTDT, in an optimized ratio yields a solution‐processed p‐channel organic semiconductor blend with carrier mobility as high as 0.65 cm² V^?1 s^?1. An optimized blending of P‐BTDT:OP‐BTDT with the n‐channel semiconductor, C₆₀, results in a BHJ ambipolar transistor with balanced carrier mobilities for holes and electrons of 0.03 and 0.02 cm² V^?1 s^?1, respectively. Furthermore, a complementary‐like inverter composed of two ambipolar thin‐film transistors is demonstrated, which achieves a gain of 115.