Operating limits of the current-regulated delta-modulatedcurrent-source PWM rectifier

A stand alone, three-phase, delta-modulated, current-source PWM rectifier has been built and has been shown to be capable of operating with near sinusoidal current waveforms, unity power factor. and good DC current regulation. A mathematical model that has been justified against experimental measurements and results from digital simulations is presented. The current waveform distortion limit and the asymptotic stability limit are established. It is shown that the rectifier can operate safely within these limits in the entire range of its power ratings     

基于脉宽调制技术的位同步

提出了一种用于数字通信的位同步方法,它是基于脉宽调制技术的间接插入导频法.推导了脉宽调制处理后信号的功率谱密度.试验结果表明,脉宽调制处理后的信号的功率谱密度中含有码元同步信号,基于脉宽调制技术的位同步方法不仅适合于双极性信号传输,还适合于单极性信号传输.该技术具有简洁、可靠的特点.     

Space Vector Sequence Investigation and Synchronization Methods for Active Front-End Rectifiers in High-Power Current-Source Drives

Space vector pulsewidth modulation (PWM) schemes for the active front end of a high-power drive normally produce low-order and suborder harmonics due to the low switching frequency and the drifting of synchronization between the PWM waveform and the rectifier input frequency. To provide a synchronized PWM and achieve the best harmonic performance, different space vector sequences suitable for a current-source converter are investigated in this paper. Details on how to achieve the waveform symmetries with a minimum switching frequency for each sequence are discussed. A thorough comparison of the harmonic performance of different space vector sequences is carried out. An optimum space vector modulation method by switching between two best sequences is proposed to achieve the best line-current total harmonic distortion with reduced switching losses. In addition, two synchronization methods, namely a PWM frame regulation method and a direct digital phase-locked loop synchronization method, are proposed. Both methods are equally effective in providing tight synchronization of the PWM waveform with the rectifier input frequency. The work has been verified in simulation and experiment.     

A novel suppressed-link rectifier-inverter topology with near unity power factor

This work describes a novel method in improving the input current total harmonic distortion (THD) as well as the power factor of a three-phase suppressed-link rectifier-inverter circuit. This proposed method makes use of only three bi-directional low power static switches with a relatively simple gating circuit. This paper illustrates how the proposed method is superior in reducing the input current THD of a rectifier-inverter set to about 5%, which is in line with the requirements of IEEE standard 519-1992. This is accomplished without the use of any filter or complex wave shaping techniques. A delta-modulated (DM) voltage source inverter (VSI) with proportional integrator forms the output stage of the converter. It helps to provide constant volts per hertz operation without the need for additional feedback circuitry and complexity. Moreover, this novel DM technique also helps to provide a smooth transition from the pulse width modulation (PWM) to square wave, hence allowing full utilization of the DC bus voltage.     

Compensated carrier PWM synchronization: a novel method to achieveself-regulation and AC unbalance compensation in AC fed converters

The compensated carrier PWM synchronization (CCPS) method for AC-fed PWM power converters is presented. The method provides a solution to PWM converters fed by industrial power systems (IPSs). Such environments usually present unbalances and magnitude fluctuations of AC voltages. Those circumstances impair standard PWM techniques because low-order harmonics are produced and DC-link regulation is poor. To reduce these undesirable effects produced by IPS, a method based on using independently compensated carriers per phase was conceived. In particular, CCPS prevents second harmonic generation and achieves converter self-regulation. The method can be used with any PWM technique and bidirectional power flow. The evaluation of CCPS is based on a complete performance comparison of a PWM rectifier with and without CCPS for various known PWM techniques     

一种数字存储组合式PWM调制方案

提出一种基于数字存储模式的PWM调制方案，讨论其非对称规则采样原理,给出宜于在线运算的简便算法，该方案采用了以EPROM为可编程定时器，并带有锁相同步功能的脉宽调制器的数字化实现方法，高开关频率基本固定，调制比与相位、频率可以独立控制，特别适用于PWM可逆整流器。     

Recursive computation of the walsh transform for delta-modulated functions

In this paper, a very simple electronic system for the recursive computation of the Walsh Transform for delta-modulated functions is presented. The proposed method avoids the need of demodulating the function.     

A line-voltage-sensorless synchronous rectifier

A line-voltage-sensorless control for three-phase pulsewidth-modulated (PWM) synchronous rectifiers is presented. A line synchronization and unity power factor control are described. Indirect synchronization without sensing the line voltage allows a standard vector-controlled inverter to be used as a synchronous rectifier without requiring any additional hardware. Furthermore, the line synchronization can be properly operated under line voltage distortion or notching and line frequency variation. All control functions are implemented with a single-chip microcontroller. It is shown via experimental results that the proposed controller gives good performance for the synchronous rectifier     

Multiplier for delta-modulated signals

A new method for multiplying delta-modulated signals by a constant is suggeated. The rate multiplier is employed here for this multiplication.     

功率因数校正器芯片电路UC3854的分析

随着开关电源越来越广泛的应用，电网的功率因数大大下降，功率因数校正成为一个新的问题。UC3854是解决这个问题的一种高性能功率因数校正器。该电路采用平均电流模型，它通过脉宽调制输出的一连串脉冲信号来控制电路开关晶体管的导通与截止，从而将输入电流与输出电压的相位重新调整到同相的状态，最终达到功率因数校正的目的。     

Combination voltage-controlled and current-controlled PWM invertersfor UPS parallel operation

In this paper, a scheme of combination of voltage-controlled and current-controlled PWM inverters for parallel operation of a single-phase uninterruptible power supply (UPS) is proposed. The voltage-controlled PWM inverter (VCPI) unit as a master is developed to keep a constant sinusoidal wave output voltage. The current-controlled PWM inverter (CCPI) units are operated as slave controlled to track the distributive current. The power distribution center (PDC) performs the function of distributing the output current of each active unit. In this proposed scheme of parallel operation, each of the units can be designed as nearly independent, and the CCPI units do not need a PLL circuit for synchronization. As a result, the parallel operation of UPS is easy to implement and to expand system capacity. For the purpose of illustration, the system, including three single-phase units which operate in parallel, is analyzed and experimental results are given     

基于△调制反馈离散时间系统的Hash函数研究

△调制反馈离散时间系统在一定的参数范围内出现混沌运动，其产生的混沌序列具有良好的伪随机性、遍历性和初值敏感性．文中基于该系统建立了一个带秘密密钥的Hash函数算法，算法以迭代初始点作为秘密密钥．实验表明：该方法简单，具有良好的单向散列性能，并能满足一定的安全性要求．     

A digital conferencing technique

A digital conferencing technique based on pseudo-addition of adaptive delta-modulated channels has been presented. It employs majority logic for routing speech signals of active subscriber to all others in conference. Time sharing allows processing of large number of channels, making it attractive for VLSI realization.     

基于Δ调制反馈离散时间系统的Hash函数研究

Δ调制反馈离散时间系统在一定的参数范围内出现混沌运动,其产生的混沌序列具有良好的伪随机性、遍历性和初值敏感性。文中基于该系统建立了一个带秘密密钥的Hash函数算法,算法以迭代初始点作为秘密密钥。实验表明:该方法简单,具有良好的单向散列性能,并能满足一定的安全性要求。     

双电机控制系统在吊放电缆寿命试验台中的应用方案

主要阐述了吊放电缆寿命试验台电机控制系统的硬件部分设计方案,其主要采用双直流电机和美国德州仪器公司的TMS320F2812构成控制系统,包括电源电路、PWM产生电路、DSP外围电路、速度控制及检测电路等硬件模块设计。该控制系统能同时驱动两台直流电机,并能精确实现同步控制。     

一种高速线阵CCD采集系统的设计

针对线阵CCD（ChargeCoupledDevice）及其外围器件时序复杂的特点,设计了一种高速线阵CCD采集系统。该系统采用MSP430单片机产生PWM信号实现各器件驱动时序,并将采集结果通过串口发送至上位机。介绍了系统组成及各器件时序同步的设计方法。实验结果表明,该线阵CCD采集系统能够很好的满足设计要求,可作为模块化电路集成到其它测量系统中。     

激光照排机场扫描控制的研究与实现

在激光照排机中,成像激光光点的坐标是由水平方向的行扫描和垂直方向的场扫描的同步运动决定的.为了提高成像激光光点的位置精度,从而提高成像质量,通过对激光照排机电机控制系统的研究,基于可在线调整参数的模糊自适应PD控制算法,运用PWM、光栅编码器及锁相环技术,设计了一套激光照排机的场扫描电机控制系统.通过自检方格的测试证明,该系统提高了激光照排机行、场扫描电机的同步控制精度,从而提高了激光照排机的成像质量.     

多电平PWM控制技术发展

多电平PWM控制技术一直是多电平变换器研究的核心内容之一。基于传统两电平PWM技术研究的经验，经过近十几年的发展，多电平PWM控制技术已形成了儿类不同的实现方法，同时新的控制方法还在涌现。与两电平相比，多电平PWM方法需要面对一些新出现的问题，并拓展PWM控制的内涵，进而形成新的PWM控制思路。按照目前的发展情况，多电平PWM控制方法一般有多电平载波PWM方法、多电平空间矢量PWM方法，以及其他优化的PWM方法。本文对已有多电平PWM控制技术进行了归纳和分析，最后指出多电平空间矢量法和载波调制法在一定条件下具有内在的一敛性。     

Minimum-loss strategy for three-phase PWM rectifier

In this paper, the conduction and switching losses of a voltage-fed three-phase pulsewidth modulation (PWM) rectifier are analyzed for various PWM schemes. On the basis of this result, a novel PWM strategy which minimizes the loss of a three-phase PWM rectifier is developed. This minimization result is derived from the following two factors: (1) less switching frequency ratio; and (2) the absence of switching in the vicinity of peak input current. As a result, it is anticipated that the switching loss of the rectifier is reduced by 46%, compared with continuous space-vector PWM rectifiers, and 20% compared with conventional discontinuous space-vector PWM rectifiers. Moreover, the proposed PWM scheme can produce the highest available output voltage because it is based on the concept of the voltage space vector. The effectiveness of the proposed PWM strategy is verified by experiments