分裂式可变调制波的PWM过调制技术及谐波分析

针对空间矢量脉宽调制(SVPWM)过调制算法复杂且涉及除法运算的问题,构建一种分裂式可变调制波,该调制波在调制度M∈[0,1]的线性区为正弦波,在M∈(1,4/π)的过调制区则分裂为两种以不同方式变化的正弦曲线段,相衔接构成一种调制波,其面积随M提升进一步扩大,直至方波。采用三角载波采样,在线性区改变调制波幅值即可线性地改变PWM基波值,在过调制区则减小两种正弦波曲线段间的分界角,继续提高PWM基波幅值大小,直至方波模式。经研究过调制区的PWM谐波影响与分界角初值的关系,得出最佳分界角初值。提出的PWM算法简单,线性区间的PWM电流总谐波畸变率(THD)与正弦脉宽调制(SPWM)一致;在M∈(1,1.2]过调制区其值仍延续低位。实验结果验证了该技术的有效性和优越性。     

一种三相软开关PWM变流器电流极性检测与电流补偿方法

对于一种基于幅相控制的三相零电压开关PWM变流器，在利用正负斜率交替的锯齿载波调制方式下，需要按照电流极性来进行锯齿载波斜率的交替翻转，由于在翻转处会造成电流畸变，也需要按照电流极性变化的时刻来补偿。该文从单位功率因数变流器的固有特点出发，在顺变和逆变状态下，提出了电流极性检测的软件实现方法，分析了使用正负斜率锯齿载波带来的电流过零点失真的原因，并给出了相应的补偿方案。该方法有效保证了软开关技术在三相PWM变流器上的实现，具有简便有效、节约硬件资源、相电流谐波较小等优点。     

三相软开关PWM逆变器载波方式的选择

详细阐述不同载波方式对PWM逆变器输出特性的影响。指出三角载波用于硬开关PWM逆变器时 ,由于死区时间的影响 ,其输出电压电流在基波频域中含有谐波成分 ;软开关PWM逆变器如果也采用三角载波 ,则不但难以控制谐振电路的起振时间 ,而且谐振电路损耗大 ,直流电压的利用率低 ;硬开关PWM逆变器采用锯齿载波调制 ,必将导致严重的电流波形失真 ;软开关PWM逆变器交替使用正负斜率锯齿载波 ,不但谐振电路的起振时间容易控制 ,而且不会导致由死区时间引起的输出电压电流波形的失真     

基于载波移相控制的单元串联多电平变频器的分析研究

简单介绍单元串联多电平变频器的拓扑结构和载波移相控制的工作原理,提出了3种不同的方法生成H桥功率模块的PWM开关信号,并分析在各个控制方式下输出电压波形和谐波成分的不同。使用MATLAB软件进行系统仿真,分析在调制比M降低时对输出相电压、线电压和电流的影响,以及谐波含量和谐波总畸变率(THD)的变化。     

三相软开关变流器电流极性鉴别与电流补偿

对于基于幅相控制的三相零电压开关PWM变流器，提出了一种电流极性鉴别与电流补偿方法。在利用正负斜率交替的锯齿载波调制方式下，需要按照电流极性来进行锯齿载波斜率的交替翻转，由于在翻转处会造成电流畸变，也需要按照电流极性变化的时刻来补偿。本文从单位功率因数变流器的固有特点出发，在顺变和逆变状态下，提出了电流极性鉴别的软件实现方法，分析了使用正负斜率锯齿载波带来的电流过零点失真的原因，并给出了相应的补偿方案。该方法有效保证了软开关技术在三相PWM变流器上的实现，具有简便有效、节约硬件资源、相电流谐波较小等优点。     

线性组合采样法SPWM新技术

针对不对称规则采样法PWM采样次数多、占用微处理器资源大的问题,提出了一种线性组合采样的新方法。该方法通过对三角载波顶点位置的调制波采样的线性组合获得载波周期内的另一采样值,使采样次数比不对称规则采样法减少一半。谐波计算结果表明新方法的PWM电压THD指标达到了不对称规则采样法PWM相同水平,并保持电压基波分量与调制度之间的线性关系。新方法的PWM算法简单,适于采用微处理器或DSP实时、在线计算。仿真结果证实了新方法的有效性。     

一种新的有源滤波器优化特定消谐PWM技术

影响有源滤波器消谐特性的重要因素是充分减小特定消谐PWM波形剩余谐波含量及其改善剩余谐波的频谱分布。特定消谐PWM波形的剩余谐波含量较大，谐波频谱分布差是它固有的缺点。为了克服特定消谐PWM技术本身的缺点，提出了一种新的优化特定消谐PWM开关角的优化解法。利用独特的优化技术将剩余谐波的第一波峰向后推移，改善输出波形的频谱分布，综合抑制有源滤波器的电流畸变率，提高装置的效率。以M＝13为例说明其优化原理，最后通过计算机仿真验证了理论的正确性。     

Opportunities for harmonic cancellation with carrier-based PWM fora two-level and multilevel cascaded inverters

Pulsewidth modulation (PWM) strategies have been the subject of many years of research effort, and the merits of the various alternatives investigated have been argued extensively. In general, it is now accepted that natural or asymmetrical regular sampled PWM with a third harmonic injected or a space-vector centered reference waveform gives the best harmonic performance, with discontinuous modulation having some advantages for higher modulation ratios. This paper uses a general analytical solution for carrier-based PWM to mathematically identify the harmonic cancellation that occurs in various PWM implementations and converter topologies. This solution provides a formal justification for the superiority of natural and asymmetrical regular sampling techniques in eliminating half of their sideband harmonics simply by virtue of their phase leg switching. Then, the use of fundamental reference phase shifting between phase legs to create single- and three-phase 1-1 output voltages is reviewed, and the harmonic cancellation that occurs is identified. One significant result from this analysis is the realization that an odd/triplen carrier/fundamental ratio has no intrinsic harmonic benefit, contrary to the generally accepted wisdom. Finally, opportunities for harmonic elimination in multilevel cascaded inverter systems by carrier phase shifting are investigated, and the optimum phase shift is identified     

基于PAM+PWM级联多电平逆变器的SVG的研究

为了使级联SVG降低开关损耗、减小谐波含量,提出了PAM(Pulse Amplitude Modulation)+PWM(Pulse Width Modulation)调制策略。四个H桥级联构成PAM单元,各H桥都工作于基频开关频率下,开关损耗较低。第五个H桥构成PWM单元,PWM单元对PAM单元输出阶梯波中的谐波分量进行补偿,极大地降低了电压电流畸变率,提高装置输出电流的质量。PAM单元直流侧采用脉冲轮换策略,有效地抑制了直流侧电压的不平衡。PWM单元采用电流直接控制策略,响应速度快,控制精度高。最后在Matlab/Simulink中建立级联SVG仿真模型,验证了所提方法的有效性。     

Investigation of harmonic currents and power factor on power rectifier circuits with nonequi-PWM and equi-PWM control (inductive load)

Lately, on the power rectifier circuit with semiconductor switching device, PWM control is generally employed for the purposes of reducing the harmonic currents on the dc side and improving the power factor of fundamental wave. In this case, the analysis of the current waveform becomes fairly complex. However, we express the PWM controlled voltage waveform by the step function, and can easily analyze the current waveform. We reported formerly some results of analysis about the waveform and harmonics of the current. In this paper, on the power rectifier circuit to which the nonequi-PWM and equi-PWM control are applied, we exactly calculate the harmonic currents on the dc and ac side, and the power factor by the use of the above analytical results. The characteristics of both control methods are compared on condition that each controlled factor of the load voltage is equal. These results are shown in the calculated charts. The following items can be seen from these charts on the power rectifier circuit: (1) The nonequi-PWM control can let the harmonic currents on the dc side decrease more than the equi-PWM control. But on the contrary, the harmonic currents on the ac side increase. Consequently, when the nonequi-PWM control is applied, the total power factor decreases by the increase of distortion factor of the current on the ac side. (2) The difference between the harmonic currents on the dc and ac side to both of the nonequi-PWM and equi-PWM control increases with the increase of controlled factor of the load voltage. © 1999 Scripta Technica, Electr Eng Jpn, 129(4): 117–125, 1999     

谐波电网电压下PWM整流器增强运行控制技术

在推导考虑5、7次谐波电网电压下脉宽调制(pulse width modulation,PWM)整流器瞬时有功和无功功率数学模型基础上,以实现输入电流无谐波或输入功率无波动为控制目标,提出两种谐波电压下PWM整流器增强运行控制方案,进而讨论不同控制目标下PWM整流器基波和谐波电流指令计算原则。为实现谐波电压下基波和谐波电流的准确控制,设计在基频同步旋转坐标系、5倍频同步旋转坐标和7倍频同步旋转坐标系下的多PI电流控制方案。最后通过1 kW PWM整流器的实验系统搭建和实验结果分析,验证理论分析的正确性以及多PI电流控制方案的有效性。     

DC-DC变换器混沌PWM原理及频谱特性分析

常规脉宽调制(PWM)的输出波形在载波频率及倍频周围含有较高谐波成分，本文基于混沌理论提出了一种新型PWM原理——混沌PWM(CPWM— Chaos-based PWM)，其三角载波信号的频率按Logistic映射函数规律变化，从而改变其谐波的频谱分布，使谐波连续均匀分布在较宽的频带范围内，抑制了由谐波引起的电磁噪声。将CPWM应用于DC-DC变换器，结果表明其电流、电压谐波幅值大大减少。     

高速动车组中PWM整流器谐波抑制方法研究

针对CRH3型动车组牵引系统的主谐波源——单相电压型PWM整流器,采用平均状态等效模型分析其谐波产生机理,在此基础上分别从主电路参数、控制策略两方面研究其谐波抑制方法,并进行相关仿真验证。仿真结果表明,载波移相技术可有效抑制牵引系统输入端电流谐波,配合其它谐波抑制措施可得到较为理想的输入电流波形,降低高速铁路对公共电网的污染。     

航空400Hz三相高功率因数PWM整流器的零静差矢量控制

提出并采用一种基于矢量控制的零静差控制方案来实现对航空400Hz三相PWM整流器的有效控制。传统的直接电流比较控制由于电流的参考信号是交流正弦波,因而存在着交流输入电流基波与输入电压有相位误差的问题。本文提出的零静差矢量控制技术,利用dq旋转坐标变换将电流参考信号设定为直流,使系统在整个输出负载范围内,交流输入电流基波相位与输入电压相位始终保持同相位、零误差,从而获得高功率因数值。在对控制方案详细分析后,采用Saber软件进行仿真验证,最后在一台航空400Hz三相PWM整流器原理样机上进行实验验证。实验表明交流输入电流基波相位完全跟踪输入电压相位,达到了较好的实际效果。     

一种三相电流型多电平PWM整流器

为了改善电流型整流器的谐波特性,提高其网侧功率因数,采用载波相移SPWM整流技术和电流型整流模块的并联扩容技术,提出一种三相电流型多电平脉宽调制整流器。采用数字信号处理器DSP实现正弦脉宽调制算法,并利用复杂逻辑可编程逻辑器件CPLD来构造多路PWM信号发生器的方法实现了整个系统的PWM控制。仿真结果验证了其工作原理的正确性,而实验结果则验证了该类三相多电平脉宽调制整流器的实际可行性。     

三相BUCK型SVPWM整流器LC振荡阻尼混合控制

为了抑制电流型PWM整流器输入侧LC滤波器谐振引起网侧电流畸变和系统振荡,提出了一种采用有源阻尼控制和改进SVPWM技术结合的控制策略。采用虚拟谐波阻尼器的有源控制策略,在控制过程中增加虚拟的等效阻尼电阻,能够在不改变基波功率流动的前提下抑制LC谐振引起的畸变和振荡。分析BUCK型PWM整流器的数学模型,比较无源阻尼和有源阻尼控制优缺点,在采用改进SVPWM的BUCK型整流器中引入有源阻尼补偿器。仿真和实验结果表明,所提出的控制方法能够有效地减小线电流畸变,改善系统稳定性,具有一定的工程实用价值。     

Waveform Distortion and Correction Circuit for PWM Inverters with Switching Lag-Times

The switching lag-time that prevents the phase shortage of inverter arms causes serious waveform distortions and fundamental voltage drops in pulsewidth-modulated inverter output. Distortions in the PWM inverter-fed induction motor system over the various frequencies of the carrier are investigated and a correction circuit with PWM potential feedback is proposed; the effectiveness of that circuit is shown by experiments.     

Optimal pulse patterns of a nine-phase voltage source PWM inverter for use with a triple three-phase wound ac motor

The authors have already described the nine-phase inverter driving system providing both the triple three-phase voltage source inverter with 180-deg conducting period and the ac motor windings with triple three-phase construction. The nine-pulse inverter driving system used three small-capacity three-phase coupling reactors having special windings for current balance and reduction of higher harmonics. In addition, for voltage control, current balance, and waveform improvement, optimal PWM pulse patterns were applied to the six-phase inverter driving system using a three-phase coupling reactor to provide double three-phase construction. In the system based on the mode in the title, the PWM control was applied to the nine-phase inverter driving system described in the foregoing. The coupling reactors in the system balance the fundamental currents of three sets of three-phase inverters and also absorb higher harmonic voltages other than 18p±1 (p = 1, 2, …) orders. The optimal pulse patterns found by the approach to make the performance index minimum using the Lagrange multiplier method can be applied to the PWM to reduce the higher harmonic currents greater than those calculated by the modulation method comparing the sinusoidal signal wave with triangular carrier signal. This system can have a larger capacity than the six-phase PWM inverter driving system in which coupling reactors absorb higher harmonic voltages other than the 12p±1 orders and also improve output current waveforms. In addition, the system includes the capacity of coupling reactors slightly larger than the six-phase PWM inverter driving system but enables operation with smaller torque ripples and electromagnetic noises in low- to high-frequency ranges.     

三相电压波形校正智能控制有源滤波器

为了使电网电压尽可能接近正弦波形,提出了一种通过校正网侧电压波形来减小电网中的谐波电流的智能控制有源滤波技术.智能芯片检测电网电压波形,再与标准正弦电压波形比较求得误差电压,该误差电压中含有电网中谐波电流的波形信息.用这个误差电压形成PWM整流器的指示电流,有源滤波器在智能芯片的控制下从电网吸收谐波电流并向电网输出基波...     

基于优化PWM的定子磁链轨迹跟踪控制研究

在异步电机的高性能控制方案中,为了降低开关损耗,采用优化脉宽调制(PWM)实现低开关频率下较小的电流谐波畸变。但在调制模式频繁切换时,优化PWM会产生电流和转矩冲击。因此,研究了将优化脉冲在线移位的闭环定子磁链轨迹跟踪控制方法,提出了由基于自控电机的降阶观测器与电机电流模型观测器组成的双观测器模型,实现了基波分量观测。结合电流谐波最小脉宽调制（CHMPWM）开关角,利用其重构参考磁链与实际磁链的差值,实现定子磁链轨迹跟踪。提出了无差拍下修正开关角小于2时的脉冲模式调整方案,消除了系统的动态调制误差,实现了低开关频率下异步电机的高性能控制。在开关频率为300 Hz以下的NPC型三电平逆变器上的仿真和试验证明了定子磁链轨迹跟踪控制策略的有效性。