A Symmetry Correcting Pulsewidth Modulator for Power Conditioning Applications

A wide variety of power converters is of the transformer-coupled push-pull type and uses pulsewidth modulation for output regulation. In designing and operating such converters, serious complications usually arise as a result of unsymmetrical switching of the two power transistors. Caused by small parameter dissymmetries of these transistors, asymmetrical switching normally drives the transformer into saturation. Resulting excessive saturation currents reduce efficiency and put a severe strain on the power transistors, which can eventually cause circuit failure. This paper presents a new pulsewidth modulator circuit which can be advantageously utilized in the design of such converters, and which can effectively cope with the aforementioned symmetry problem. Symmetry correction is accomplished by monitoring the two primary currents and by providing proper feedback of the integrated difference between these two currents.     

A High-Performance Pulsewidth Modulator for an Inverter-Fed Drive System Using a Microcomputer

An Intel 8086 microcomputer-based pulsewidth modulator (PWM) is described which receives digital voltage and frequency commands independently at the input, generates precision three- phase PWM waves at the output, and can be used to drive a transistor or thyristor inverter for ac drive systems. A computation intensive uniform sampling technique is used in the low-frequency region, whereas the higher frequency region is based on word recognition and pattern retrieval method. A laboratory breadboard of the modulator has been built and tested for the frequency range 0-250 Hz with resolution of 0.0077 Hz and smooth voltage variation up to square wave within a one-percent step in the whole range. The modulator has been extensively tested with a transistor inverter and hybrid computer simulated induction motor drive system and shows performance improvement over the currently available techniques.     

混合封装三相桥式电力电子集成模块研究

采用混合封装工艺的电力电子集成技术研制成一台40kW全数字化控制的变频调速用三相桥式电力电子集成模块。本文详述了该模块的内部结构及其特点,并结合变频调速的不同领域给出了全数字化恒压频比控制和转差型矢量控制的实验波形。实验结果表明,该模块具有体积小、功率密度高、应用简便灵活等特点,充分验证了电力电子集成思想的可行性。     

Characterization of Programmed-Waveform Pulsewidth Modulation

Programmed-waveform pulsewidth modulated (PWM) waveforms, applicable to ac-dc/dc-ac converters, are synthesized and analyzed in terms of several structural parameters. By invoking sensitivity studies and heuristics, optimal PWM structures are identified and contrasted. The results show total harmonic performance as a function of switching levels, waveform types, commutations per cycle, and filter bandpass.     

Advanced Pulsewidth Modulated Inverter Techniques

Since its introduction in the mid 1960's the pulsewidth modulated (PWM) inverter has offered a number of significant advantages over other inverter types for low and medium frequency applications. The generation of an acceptable waveform at higher frequency, however, was limited by the characteristics of available power thyristors and modulator design. With the advent of the fast turn-off thyristor and advances in PWM modulator techniques, the PWM inverter now offers application advantages to 200 Hz. PWM design considerations are analyzed, with a discussion of second-generation PWM operation provided.     

一种新型的混合有源滤波器智能集成驱动电路

提出一种用于混合有源滤波器的智能集成驱动电路。该驱动电路由瑞士SCALE集成驱动器件2SD315A构成,集驱动、保护、隔离功能为一体,功能强大、设计简单、稳定可靠,是一种很有应用前景的电力电子驱动电路。实验结果表明,混合有源滤波器采用智能集成驱动电路对整个滤波装置的滤波性能及安全稳定运行起到了重要的作用。     

Optimal Pulsewidth Modulation for Current Source Inverters

Two different pulsewidth modulation (PWM) schemes for current source inverters (CSI) are described. The first one is based on off-line optimization of individual switching angles and requires a microprocessor for implementation and the second one uses a special subharmonic modulation and could be implemented with analog and medium-scale integration (MSI) digital circuits. When CSI's are used in ac motor drives, the optimal PWM pattern depends on the performance criteria being used, which in turn depend on the drive application. In this paper four different performance criteria are considered: 1) current or torque harmonic elimination, 2) current harmonic minimization, 3) speed ripple minimization, and 4) position error minimization. As an example a self-controlled synchronous motor (SCSM) supplied by the PWM CSI is considered. The performance of the CSI-SCSM with the optimal PWM schemes proposed herein are compared with that using a conventional 120° quasi-square wave current.     

A Sinusoidal Pulsewidth Modulated Three-Phase AC to DC Converter-Fed DC Motor Drive

The external performances such as power factor, displacement factor, harmonic factor, and ripple factor of a three-phase ac to dc converter-fed separately excited dc motor drive employing sinusoidal pulsewidth modulation (SPWM) control technique are obtained for different speeds and modulation indexes. Since separately excited dc motors with armature voltage control provide constant torque operation, the external performance is also determined for the drive motor operating at different values of constant load torque. Motoring and regenerating operations of the dc drive machine are considered. The three-phase PWM converter-motor drive system is analyzed, taking commutation effects into account in motoring and regenerating operations. The analysis has revealed 27 common modes in one repetitive period of the output voltage. The sequence of modes for all pulses in one period of the output voltage is established. Experimental oscillograms of typical waveforms from a laboratory-sized dc motor are illustrated to verify the basic principles of operation. Although the converter circuit requires some additional components in comparison with the commonly used phase-controlled converter, the improved performance characteristics make it attractive for industrial applications involving large power ratings.     

A Hybrid Metaheuristic Algorithm for the Integrated Vehicle Routing and Three-Dimensional Container-Loading Problem

This paper examines a recently addressed practical variant of the capacitated vehicle routing problem (VRP) called the Capacitated Vehicle Routing Problem with 3-D Loading Constraints (3L-CVRP). This problem considers customer demand to be formed by 3-D rectangular items. Additional loading constraints often encountered in real-life applications of transportation logistics are imposed on the examined problem model. In addition to 3L-CVRP, we also introduce and solve a new practical problem version that was dictated by a transportation logistics company and covers cases in which transported items are manually unloaded from the loading spaces of the vehicles. Both problem versions are solved by a hybrid metaheuristic methodology that combines the strategies of tabu search (TS) and guided local search (GLS). The loading characteristics are tackled by employing a collection of packing heuristics. The proposed algorithm's robustness was tested for both problem versions, solving benchmark instances derived from the literature and new benchmark problems with diverse features in terms of customer set size and transported-item dimensions. It produced fine results, improving most of the best solutions that were previously reported.      

Optimal Pulsewidth Modulation for Feeding AC Motors

A pulsewidth modulation (PWM) technique is proposed, intended particularly for the reduction of the harmful effects of the harmonics in the inverter-fed drive systems. The approach is based on the minimization of the rms value of the current harmonics in the motor by a proper choice of the commutation angles. Switching patterns are calculated for a different number of commutations per period, for both single-phase and three-phase half-bridge inverters. In the case of the single-phase, an analytical procedure is developed which simplifies the computations. Comparisons are made of the results thus obtained with those given by other PWM techniques in use.     

Pulsewidth Modulation of Neutral-Point-Clamped Indirect Matrix Converter

An indirect matrix converter is an alternative “all-semiconductor” energy processor proposed recently for converting an ac source with fixed magnitude and frequency to a variable voltage and frequency supply that can meet the requirements of a particular industry application. In principle, an indirect matrix converter is constructed by connecting a front-end bidirectional rectification stage to a conventional two-level inversion stage with no bulky capacitive or inductive energy storage connected to their intermediate dc link. Through the proper modulation and compensation of the resulting converter, sinusoidal input current and output voltage can be achieved with minimized rectification switching loss, rendering the indirect matrix converter as a competitive choice for interfacing the utility grid to, e.g., defense facilities that require a different frequency supply. As an improvement, an indirect matrix converter assembled using a three-level energy processing stage has briefly been mentioned in the literature, but has neither been tested in simulation nor experimentally because its operational principles, pulsewidth-modulation (PWM) control, and index compensation have not yet been discussed in the existing literature. Addressing the previously described issues, this paper focuses on the operational mode analysis of a three-level indirect matrix converter implemented using a neutral-point-clamped inversion stage and the design of a number of PWM and modulation ratio compensation schemes for controlling the converter with improved waveform quality. The performances and practicalities of the designed schemes are verified in simulation and experimentally using an implemented laboratory prototype with some representative results captured and presented in this paper.      

梯形脉宽调制型逆变器的单片机控制

本文提出了用梯形脉宽调制（ＴＰＷＭ）降低逆变器谐波的一种新方法。在逆变器中，较正弦脉宽调制（ＳＰＷＭ）方法它体现优越的谐波控制性能。对梯形调制信号的三相ＰＷＭ逆变器输出波形从理论和实验两个方面作了研究。     

Pulsewidth Modulated Inverter Motor Drives with Improved Modulation

The performance of inverter drives, which use the pulsewidth modulated (PWM) technique to control motor applied voltage and frequency, are critically influenced by the choice of the modulation policy used in the control circuits. This paper deals with practical inverter drives for squirrel cage induction motors and presents some basic considerations on modulation requirements. The advantages and limitations of popular modulation methods are discussed, and an improved modulation scheme, which allows us to extend the practical speed range of PWM ac drives, is presented.     

基于EPROM存储的廉价的数字式SPWM调制器

文章提出了一种新型廉价的基于EPROM存储的数字式SPWM调制器,该类调制器可适应于多种调制方法,控制精度可根据需要自由选择,电路简单、成本极低。特别适用于USP、太阳能户用逆变电源等逆变电路中使用。文章还介绍了其原理,并将其应用于振动棒专用逆变器中,所得波形满足要求。     

一种高性能的正弦脉宽调制器

基于正弦脉调制的基本原理,本文提出了一种新型的正弦脉宽调制器。只由４片集成电路组成。具有简单、实用、可靠、实时悸好、调制精度高、价格低廉、不占用微机资源等优点。并且可以很方便地扩展为单相全桥及三相的正弦脉宽调制器,文中都作了详细的介绍。该调制器已应用到４００Ｈｚ静止变频电源中。     

一种新颖的固态高压线性调制器

介绍了一种新颖的大功率固态高压线性调制器,阐述了其工作原理、设计方法及工作特点,并给出仿真和实验结果。     

Several Modulation Techniques for a Pulsewidth Modulated Inverter

Pulsewidth modulation of a six-step inverter can be accomplished in different ways. Comparisons between different modulation techniques are based primarily on harmonic content in the output waveform and circuit constraints imposed by semiconductor characteristics. Adaptive ratio is a modulation scheme which combines the beneficial features of several available techniques and makes the necessary compromises to optimize the operating characteristics of a modulated six-step inverter.     

基于∑-△调制器的数据采集技术

由于传统的∑-△A/D转换器在应用中不够灵活,本文在简要介绍了∑-△转换的原理之后给出了一种新的∑-△调制器 DSP的转换系统构架,由DSP编程实现抽取滤波器操作,从而提高了应用的灵活性.     

一种新型光IQ调制器自动偏压控制方法

提出一种新型的适用于光OFDM调制的IQ调制器自动偏压控制方法。通过在偏置电压上添加低频扰动信号,探测其1,2阶谐波分量的强度并据此调节偏置电压,可使调制器工作在最佳偏置点。此方法结构简单,可用低速器件实现,在最佳偏置点处具有更高的灵敏度。仿真以及实验结果表明此方法可以更精确的将偏置电压调至最佳点,且扰动信号导致的信噪比代价可被忽略。