High-frequency electromagnetic processes in electrical machines under pulse-width voltage modulation

The paper considers models and features of electromagnetic processes in systems, including electrical machines and semiconductor PWM converters. It is shown that tagging into account parameters and characteristics of high frequency electric processes is necessary in designing new electrical systems.     

一种单相正弦脉宽调制逆变电源的设计

介绍了一种高品质单相正弦波输出逆变电源的设计。研究了通过中断功率通量和调节占空比的方法来改变驱动电压脉冲宽度,调整和稳定输出电压,并设计了具体的数字控制电路。通过试验样机的调试和试验,验证了设计合理可行,电路工作稳定,输出电压波形平滑,具有较好的正弦度。     

Application of voltage-supply inverter with pulse-width modulation for control of actuating inductance motor

The possibility of using a three-phase voltage-supply inverter (VSI) with pulse-width modulation (PWM) to form two-phase voltage is analyzed with a reference to the actuating induction motor (AIM) control. The VSI control algorithms that realize methods of the AIM speed control are described. Results of the harmonic analysis of the VSI output voltage and its power supply characteristics are given, as well as the computer simulation results.     

非理想电网下逆变器并网电流质量改善策略

逆变器在非理想的电网条件下采用传统的电网电压前馈控制时,其输出阻抗的相位裕度很低,且不能很好地抑制电网电压的谐波传入控制系统,从而很难保证其并网电流的质量。提出了一种改善在非理想电网条件下逆变器并网电流质量的方法。首先,建立PR控制下采用传统电网电压前馈的LCL型逆变器输出阻抗模型,提出利用带通滤波器改进的电网电压前馈策略,提高逆变器对电网阻抗的鲁棒性。同时在PR控制器上并联多次谐波补偿器,使其不仅能够提高逆变器对电网阻抗的鲁棒性而且能够有效地抑制电网电压谐波对逆变器并网电流的干扰,从而改善非理想电网条件下的逆变器并网电流的质量。最后,利用仿真和实验验证了所提方法的有效性。     

三电平电压型逆变器空间矢量调制算法的研究

本文提出一种三电平逆变电路空间矢量调制的算法。在每个控制周期中加入固定作用时间的输出矢量111，避免了在参考矢量切换扇区时可能出现的矢量突变问题。由于输出矢量的选择和作用时间的计算都是在静止的α-β坐标系下完成，这种算法避免了常规空间矢量调试算法中复杂的三角函数的运算，只需要简单的算述运算即可实现空间矢量的调制。此外，还提出一种简单易行的中点电位控制方法实现了中点电位稳定。仿真和实验结果证明了所提出算法的有效性。     

Research and development of conversion of direct current voltage to the quasi-sinusoidal voltage with pulse-width modulation

Practically all widely used variable-frequency alternating-current electric drives with autonomous voltage inverters (AVIs) use pulse-width modulation (PWM) according to one of the following techniques: sinusoidal, space-vector, and relay. Fulfilling the relay PWM requires an analog–digital converter (ADC) with high resolution and sample rate. Vector PWM has a nonsinusoidal output voltage that causes additional losses in the motor. The main problem of a symmetrical (centered) sinusoidal PWM is underuse of a dc link. For a long time, the vector PWM method was taken to be most promising one due to the absence of this defect. In practice, this technique is applied in areas without a strong voltage criterion, for which reason it has limited use. Moreover, due to another significant problem, which is the “dead” time on the sector borders at the vector PWM, different modified methods for constructing the sinusoidal PWM have become widespread, especially in modern asynchronous motor control systems, with the development of digital microprocessor systems. To determine the quality of different types of PWMs, a complex model of an electric drive, incorporating an inverter control system that implements different algorithms of constructing the discrete PWM signals is developed. The model and the electric circuit are constructed in LabVIEW and NI Multisim, respectively. The obtained simulation data can be used to select the optimal method of controlling the AVI. The analysis that has been conducted allows one to select an optimal PFWM control strategy in terms of research results concerning electric power quality and mechanical properties.     

Analysis of stability and accuracy of a pulse-width current controller of an autonomous three-phase inverter

In this paper, a closed current control loop in a three-phase circuit consisting of electromotive force and inductive loads is considered. Difference equations for the loop are obtained. The stability and accuracy of the loop are investigated. Ways to increase the current control accuracy are found.     

Improved voltage source inverter with 18-step output waveforms

In this article, an improved voltage source inverter is proposed. This circuit is based on the NPC (neutral point clamped) inverter. By dividing the input DC source into four sections and adding four auxiliary switching elements, the proposed circuit can be performed as if an 18-step inverter as far as the harmonic components in the AC output voltages are concerned. The performances of the proposed circuit and the output AC voltage waveforms are discussed. Then the optimum conditions are determined by minimizing the distortion of the output waveform, and the effects for the harmonic reductions can be clarified by theoretical results. The ratings of circuit components, such as the separated DC sources and the switching devices, should be investigated. Moreover, we suggest the adjusting methods of the output voltages     

多电平电压源逆变器降低共模电压的脉宽调制策略的研究

多电平逆变器因为存在的开关状态多,因此其调制方法也较为复杂。通过选择适当的开关状态,部分共模电压降低调制方法(PCMVPWM)能将共模电压降低到直流侧电源的1/3,而完全共模电压消除调制方法(FCMVPWM)能够完全消除共模电压。本文主要揭示了这两种调制方法与基于载波的脉宽调制的关系并进行仿真比较。最后,在实验室建立的NPC三电平逆变器的原型机上对算法进行了实验验证,结果表明该调制方法能够有效地降低共模电压。     

基于等效电路模型的新型三电平逆变器载波调制方法的研究

提出了一种新型的基于三角载波水平移相的三电平逆变器PWM调制方法。通过分析三电平电压型逆变器主电路结构,建立了相应的等效模型,给出了一种提高等效开关频率的具有二重化特点的载波水平移相调制算法。该调制方法与三电平逆变器空间矢量方法相比,其具有计算简单、实现简单等优点,与一般载波垂直移相调制算法相比,其具有低次谐波小、等效开关频率提高一倍、容易滤波等优点。通过仿真研究,验证了该调制方法的可行性。通过建立等效模型为采用两电平三相逆变器各种调制算法来实现三电平逆变器的控制奠定了研究基础。     

电压型逆变器输出波形控制技术

本文介绍了目前电压源型逆变器输出波形控制的主要控制方法，总体上可分为：基于周期的控制和瞬时值反馈控制。在此基础上，分析了各种控制方法相应的优点和缺点。从波形控制目前的研究实际出发，提出了两种较有前途的方案：结合鲁棒观测器的反馈控制技术和重复控制的反馈控制技术。     

不平衡电网下逆变器功率波动/电流质量协调控制

电网电压不平衡条件下系统的输出功率和电流质量是并网逆变器的主要关注指标。首先对两种控制目标下对应的参考电流进行量化分析。在此分析的基础上,提出一种功率波动抑制与电流平衡协调控制策略。该控制策略采用降阶谐振器提取参考电流中的谐波信号,利用一个权重系数调节参考电流中谐波分量的大小,基于无差拍电流控制实现提出的策略。该方法无需使用锁相环和正负序分离模块,利用瞬时电压计算电流参考值,简化了控制结构。通过Matlab/Simulink仿真和RT-LAB半实物实验平台,验证了控制策略的有效性和可行性。     

A novel PWM scheme for a three-level voltage source inverter withGTO thyristors

This paper presents a new PWM method for the three-level GTO inverters based on the space voltage vectors. With the proposed PWM method, we can minimize the harmonic components of the output voltage by avoiding the minimum pulse width limitation problem of the GTO thyristors and keeping the voltage balancing of the DC-link capacitors. The principle of the proposed PWM method and the voltage vector output sequences are described in detail. Computer simulation and experimental results verify that the proposed PWM method is suitable for high voltage and large capacity three-level GTO inverters applied to induction motor drives     

Dynamic analysis of LLCC parallel resonant converter under pulse-width modulation control

Contents The large and small signal dynamic analysis of LLCC-type parallel resonant converter operating in continous-conduction mode under fixed frequency, variable duty-ratio (pulse-width modulation) control is presented in this paper. The nonlinear and small-signal equations of the converter including the supply and output rectifiers are derived. The influence of the converter operation on the supply input power factor and how the input rectifier affects the small-signal dynamics of the converter are discussed.

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Dynamische Analyse von LLCC Parallel-Resonanz-Umrichtern bei Puls-Weiten-Modulation

Übersicht Die dynamische Groß- und Kleinsignalanalyse von LLCC Parallel-Resonanz-Umrichtern im nicht lückenden Betrieb bei fester Frequenz und Puls-Weiten-Modulation wird dargestellt. Die Gleichungen für nichtlineares und Kleinsignalverhalten des Umrichters unter Berücksichtigung der Eingangs- und Ausgangsgleichrichter werden abgeleitet. Der Einfluß des Umrichters auf den Leistungsfaktor am Eingang und die Wirkung des Eingangsgleichrichters auf die Kleinsignaldynamik des Umrichters werden diskutiert.

     

On the performance characteristics of a synchronous motor fed from a voltage source inverter

Contents Using two axis model the steady state characteristics of a voltage controlled synchronous motor drive are investigated for different modes of operation based on signal flow graph technique. The input voltages are assumed to be quasi square wave. The analysis shows that depending upon the mode employed the machine can be made to possess shunt, series or mixed characteristic. The torque developed is of pulsating nature. All the modes of operation have sixth harmonic pulsations which are roughly 20 percent of the mean value. A voltage fed motor is found to have reduced torque pulsations when compared to a current fed one with the same flux levels.

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Über das Betriebsverhalten eines Synchronmotors mit Spannungszwischenkreisumrichter

Übersicht Aufgrund des Signalfußdiagramms wird das stationäre Verhalten des Spannungsgespeisten Synchronmotorantriebs bei rechteckförmiger Spannung für verschiedene Betricbsarten der Maschine untersucht. Dafür werden die Gleichungen der Maschine auf der Basis des Zweiachsenmodells aufgestellt. Die Untersuchungen zeigen, daß das Drehmoment Schwankungen hat, deren Amplitude um etwa 20 Prozent des Mittelwerts liegen. Weiter wird gezeigt, daß diese Schwankungen kleiner als die des stromgespeisten Synchronmotors sind. Je nach der Betriebsart besitzt die Maschine eine Drehmoment-Drehzahl Kennlinie, die der des Nebenschluß- oder Reihenschlußmotors ähnlich ist.

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Nomenclature i _d ,i _q direct and quadrature axis components of stator current - i _D ,i _Q direct and quadrature axis components of damper currents - l _d ,l _q synchronous inductances of direct and quadrature axes respectively - l _D ,l _Q self inductances of damper windings - l _hD ,l _hQ mutual inductances between stator and damper windings - l _hd mutual inductance between armature and field in the direct axis - L _af mutual inductance between phasea and field winding - p operator - P pairs of poles - r _a armature resistance - r _f field resistance - r _D ,r _Q damper winding resistances in the direct and quadrature axes respectively - s Laplace operator - u _d ,u _q direct and quadrature axis components of stator voltages - _d , _q direct and quadrature axis components of stator flux linkages - _D , _Q damper flux linkages in the direct and quadrature axes - _f field flux linkages - synchronous angular velocity     

考虑母线电压滤波的逆变器自抗扰控制器设计

在永磁直驱风力发电并网系统中,通常将逆变器直流母线电压作为电压外环控制目标,由于测量误差及噪声的存在,常用惯性环节滤波后的母线电压作为反馈。在典型的电压外环自抗扰控制系统中,因未考虑滤波器的影响,使得控制反馈与实际系统输出存在幅值相位差异,进而影响系统控制性能。文章将通过一阶惯性环节滤波的信号扩张成新的状态变量,由改进的线性扩张状态观测器对滤波前母线电压进行估计并反馈,可消除因惯性环节导致的母线电压纹波。实验仿真表明,系统在观测噪声扰动和电网侧电压故障情况下具有较强的抗干扰性能。     

A new digital control method for a voltage source inverter to compensate for imbalance of output voltage

This paper provides a new signal compensation method for digital inverters, which is aimed at improving the voltage source inverter. Because of the non‐ideal characteristics of components of the inverter (e.g., metal oxide semiconductor field‐effect transistor module), the output voltage is unequal at positive and negative half cycles. This will result in inductive load saturation, and the switches will be damaged. The method proposed in this paper utilizes a combination of pulse signal and reference signal for adjusting the height and the width of pulse signal, with small direct current offset compensated by the average voltage of the signal. This method can also be adopted in a built‐in, low‐resolution pulse width modulation digital controller, which has advantages such as automatic compensation of output voltage and low cost. Copyright © 2012 John Wiley & Sons, Ltd.     

电网不平衡情况下基于神经网络并网逆变器同步技术研究

为解决常规锁相环技术在电网电压不平衡情况下难以对电网电压频率和相位进行有效检测的问题,提出一种电网不平衡情况下基于神经网络的并网逆变器同步算法。首先,在两相静止坐标系下推导电网电压状态方程,并基于此建立神经网络;然后,利用网络输出电压矢量和实际电压矢量误差进行在线调整权值,并利用权值调整计算在线辨识电网电压频率、相位和幅值,从而可以构建电网电压的正负序分量。仿真和实验结果表明:该方法能在电网不平衡情况下快速有效在线自适应辨识电网电压频率和相位,提取电网电压正负序分量,具有较强的鲁棒性。