拉格朗日插值法光伏并网逆变器无差拍控制

采用拉格朗日二阶多项式插值法,用于提高无差拍控制算法的电流预测精度;针对单相并网逆变器采用单极倍频SPWM方法,使逆变器在不提高开关频率情况下的电流高次谐波频率加倍,总谐波含量减少。仿真与实验结果表明,该方案能有效地实现逆变器入网电流的低谐波含量、高功率因数与快速动态调节。     

基于QROGI的永磁同步风力发电机定子电流谐波抑制方法

针对永磁同步风力发电机驱动系统中定子电流谐波的问题,提出一种基于准降阶广义积分器（QROGI）的电流谐波抑制方法。将QROGI控制器引入电机控制电流环,利用QROGI控制器在设定交流频率处的高增益以抑制谐波电流;针对旋转坐标系下谐波电流分量在交直轴上表征为交流量,通过在电流内环叠加QROGI控制器实现对谐波电流的控制;对叠加QROGI的电流环控制器进行详细理论分析,对电流环控制器参数进行设计,给出详细的分析过程及控制器参数定量计算方法。最后通过搭建半实物实验平台验证了所提方法能够对永磁同步风力发电机定子谐波电流进行有效抑制。     

双PWM全功率变流器机侧控制策略研究

双脉宽调制(PWM)全功率变流器机侧的开关频率低,其电流谐波含量高,且同步电机反电动势中产生了大量谐波.为了降低发电机的铜铁损耗,降低系统成本,弱化网侧滤波器设计的难度,抑制机侧谐波具有重要意义.传统比例积分(PI)调节器难以抑制直驱永磁同步发电系统机侧谐波,针对这一现象,提出将PI与准比例谐振(PR)调节器联合,形成新型的调节器,并在转子定向的旋转坐标系下对定子电流特定次谐波进行了抑制.运用PSCAD/EMTDC软件进行了仿真验证,结果表明:采用经典PI控制时,机侧电流谐波含量为17.28%;采用新型调节器时,机侧电流谐波含量为5.86%.同时,通过分析实验结果验证了该机侧控制策略的可行性,可有效地抑制机侧谐波.     

光伏发电系统低功率运行并网电流谐波抑制研究

以低功率运行的光伏发电系统为研究对象,通过理论分析和实验研究的方法,对光伏发电系统低功率运行时并网逆变器输出电流畸变恶化的问题进行探讨,并设计一种减小并网电流谐波的解决方案,最后进行实验验证。结果表明:提出的解决方案可有效减小并网逆变器低功率运行时输出的低次电流谐波,实现光伏发电系统低功率运行时并网电流总谐波畸变率满足IEEE Std.1547-2003标准。     

低开关频率下三电平自然采样SVM算法的研究

为了降低大型光伏电站应用场合中的变换装置功耗,需降低器件开关频率,但低开关频率会引起输出电流低次谐波含量增大,影响输出电能质量。针对大型光伏电站中传统三电平逆变器空间矢量PWM(SVM)策略在低开关频率时低次谐波含量过高的问题,提出了将自然采样与SVM相结合的三电平自然采样SVM(NS-SVM)算法,并根据牛顿-拉夫逊迭代法简化了该算法,达到了快速在线数字实现。所提出的三电平NS-SVM算法相对于传统三电平SVM在低开关频率下具有更好的低次谐波性能,使得输出电流总谐波畸变率(THD)明显改善。最后通过Matlab/Simulink仿真验证了该调制策略的有效性。     

基于谐波提取器的永磁同步电机谐波抑制方法

永磁同步电机(Permanent magnet synchronous motor,PMSM)在运行时由于受到逆变器的非线性因素影响导致电机定子电流产生谐波,使电机产生额外损耗.由于传统PI(Proportion integration,PI)控制器不能无静差跟踪交流信号,会导致谐波检测精度不高.针对这种问题,提出一种...     

Z-域下基于快速谐波电流检测的有源滤波器设计方法

为提高有源滤波器(active power filter,APF)的动态响应和补偿性能,提出一种Z-域下基于快速谐波电流检测的控制策略。谐波电流检测环节采用特定次谐波陷波器和低通滤波器的组合滤波器,特定次谐波陷波器滤除低次谐波,低通滤波器频带较宽,滤除高次谐波,可有效解决传统滤波器的带宽和响应时间上的矛盾。电流控制环在基波dq同步旋转坐标系下,将基波电流与谐波电流分开控制,谐波电流采用矢量谐振控制器,并在离散域下进行参数设计,可避免数字化过程中引入的偏差。通过仿真和实验结果验证该方法能够快速分离谐波电流,在负载波动时能保持直流侧电压稳定并实现较好的补偿效果。     

Halbach阵列在直驱、半直驱风力发电机的应用

文章将Halbach阵列应用于直驱、半直驱风力发电机,以减轻电机质量。利用有限元分析法对1.5 MW直驱和半直驱永磁同步风力发电机建模,选取不同的充磁方式、极对数、气隙长度、电机尺寸进行仿真,通过傅里叶分解变换提取气隙磁密基波和谐波含量,进而对基于Halbach阵列的发电机静态气隙磁场进行分析比较。仿真结果表明,Halbach阵列发电机气隙磁密谐波含量少,基波含量高,波形更接近正弦,尤其在电机极数为70~90表现优异。     

基于粒子群算法的光储微电网谐波电流抑制参数组寻优策略

单相逆变器负荷的瞬时功率含有二倍频脉动功率分量,导致输入源中存在二次谐波电流。以光储微电网为例,提出基于陷波器和准比例谐振控制器的谐波电流抑制方法。在陷波器和准比例谐振控制器的作用下,电感支路表现出在二倍频处呈现高阻抗、非二倍频处呈现低阻抗的差异化特性,既实现了二次谐波电流的抑制,又满足了动态性的需求。针对该控制器参数选取不当导致动态性变差和谐波抑制能力下降等问题,提出基于粒子群算法的抑制参数组寻优策略,利用其精度高和收敛速度快的优点,获得兼顾动态品质、稳定性及谐波抑制能力的最优抑制参数组。实验结果验证了所提方法和寻优策略的有效性。     

绕组开放式永磁发电机系统整流桥电压矢量补偿控制方法

针对绕组开放式永磁发电机结合逆变器-整流桥拓扑构成的新型发电系统中由于整流桥的存在导致的发电机绕组中存在较多谐波含量的问题,分析了系统中电机绕组电流谐波的产生原因及其组成部分,根据整流桥输入电压矢量与电流状态的对应关系,对逆变器和整流桥的电压空间矢量进行合成,提出了一种基于整流桥电压空间矢量补偿的新型控制策略,消除了整流桥的非线性影响,实现绕组开放式永磁发电机系统的高效率运行。     

The elimination of leakage currents in the neutral point clamped photovoltaic grid-connected inverter by the improved space vector pulse width modulation method

In this paper, the reason of high-frequency leakage current in neutral point clamped photovoltaic grid-connected inverters that adopts traditional modulations is analysed. In order to solve the problem, this article puts forward two improved methods based on the three-level space vector pulse width modulation (SVPWM), which can reduce the leakage current by applying three medium vectors or using only two medium vectors and one specific zero vector to compose the reference vector. In addition, the system control method adopts the coordination control of the current inner loop and the DC voltage outer loop, which can reduce voltage fluctuation at the DC side. Thereby, the suppression of leakage current can be realised without requiring any modification on the multilevel inverter. Compared with the traditional three-level sinusoidal pulse width modulation (SPWM) and SVPWM, the two new methods are advantageous in having a stable common-mode voltage, low leakage current, and low harmonic component of grid current. The theoretical analysis and results show the effectiveness of the proposed methods.     

An optimized SVPWM switching strategy for three-level NPC VSI and a novel switching strategy for three-level two-quadrant chopper to stabilize the voltage of capacitors

Voltage source inverter (VSI) can produce single and three-phase (3P) AC voltages from a constant or variable DC voltage. There are many ways to control the VSI output voltage. Each control way produces some harmonics at the VSI output voltage. The space vector pulse width modulation (SVPWM) may be more effective than other modulation methods, e.g. harmonic injection, phase shifting, multi career pulse width modulation, in decreasing the low order harmonics (LOH). Different switching strategies (SSs) of power electronic devices in SVPWM have some specific advantages and disadvantages with regard to one another. In this paper, a comparative study between different SVPWM SSs is carried out by considering some objective functions such as total harmonic distortion (THD), power and switching losses, the ratio of the harmonic components to the fundamental component, distortion factor (DF). It is also shown that by selecting an optimized and appropriate SS for SVPWM, the harmonic orders, which are the multiples of the frequency index (FI), are eliminated. Then, to investigate the impact of variations of the capacitors voltage and switching frequency on power quality criteria, the most appropriate and optimized SS is applied to a 3P three-level (3L) neutral-point-clamped (NPC) VSI to supply a 3P load.     

采用VSC-HVDC的海上风电场柔性直流输电系统控制策略研究

以实际应用于海上风电输电工程中的三相两电平电压源换流器为研究对象,通过对换流器主电路拓扑结构进行坐标变换,建立了便于解析的两相旋转dq坐标系下的数学模型;换流器控制系统采用了双闭环PI控制方法,并引入电流解耦控制,实现了一侧定有功、一侧定直流电压控制,提高了系统的动态性能和抗干扰能力;采用了SVPWM调制方式进行调制,有效地降低了谐波含量和开关损耗;采用Matlab/Simulink仿真,并搭建了3.5 kW试验验证平台。结果表明该方案控制效果良好,电压、电流波形稳定、谐波含量少且响应速度较快。因此,适用于海上风电场柔性直流输电系统。     

三端口LLC谐振型变换器研究

为解决多个变换器引起的能量损耗问题,提出一种三端口LLC谐振型结构的变换器,可实现同时向负载端和储能端供能.建立基波近似(FHA)模型,分析变换器的增益特性.传统的脉冲宽度调制(PWM)策略无法实现宽范围零电压开关(ZVS)技术,现有的脉冲频率调制(PFM)控制策略需要复杂的建模过程.研究中设计了改进的PWM-PFM混...     

一种基于PSCAD/EMTDC仿真平台的SVPWM逆变器控制算法

空间矢量脉宽调制法(SVPWM)比传统的正弦脉宽调制法(SPWM)具有较高的直流电压利用率以及较低的输出波形失真度。介绍了三相逆变器的SVPWM控制算法,建立了基于PSCAD/EMTDC仿真平台的三相逆变器模型,并给出了基于PSCAD/EMTDC仿真平台的SVPWM优化控制算法。通过建立一个控制系统来进行仿真和研究,给出了仿真线电压及相电压波形。仿真结果充分显示了SVPWM技术应用于大功率场合的优点。     

Digital power factor control and reactive power regulation for grid-connected photovoltaic inverter

The overall efficiency of photovoltaic (PV) systems connected to the grid depends on the efficiency of direct current (DC) of the solar modules to alternate current (AC) inverter conversion. The requirements for inverter connection include: maximum power point, high efficiency, control power injected into the grid, high power factor and low total harmonic distortion of the currents injected into the grid. An approach to power factor control and reactive power regulation for PV systems connected to the grid using field programmable gate array (FPGA) is proposed. According to the grid demands; both the injected active and reactive powers are controlled.In this paper, a new digital control strategy for a single-phase inverter is carried out. This control strategy is based on the phase shift between the inverter output voltage and the grid voltage, and the digital sinusoidal pulse width modulation (DSPWM) patterns, in order to control the power factor for a wide range of the inverter output current and consequently the control and the regulation of the reactive power will be achieved. The advantage of the proposed control strategy is its implementation around simple digital circuits.In this work, a simulation study of this strategy has been realized using Matlab/Simulink and PSIM. In order to validate its performance, this control has been implemented in a FPGA. Experimental tests have been carried out demonstrating the viability of this control in order to control the power factor and the injected power into the grid.     

An online optimal approach to PWM-SHE gating signal generation

A simple and low-cost method of generating the pulse width modulation specific harmonic elimination (PWM-SHE) switching signals to drive the three-phase voltage source inverter (VSI) is presented. This novel approach computes the switching angles online using a PC and provides the flexibility of eliminating different sets of VSI output harmonics in a quick and easy manner without any hardware change. The validity of selected result has been verified experimentally     

电控组合泵喷油驱动电路设计及试验分析

为了提高电控组合泵喷油电磁阀的高速驱动性能,采用分析和试验相结合的方法设计了一种具有双电压自动切换的双阶段脉冲宽度调制(PWM)波限流控制功能的驱动模块,并在油泵试验台架上进行了多项参数试验和分析.试验结果表明:对于作用电流为18A的电磁阀,在高压值为100V、高压作用时间为290μs时,其驱动电流上升率高且不造成能量损耗;PWM波频率取值约100kHz时既能减小电流波动又能克服干扰;与单纯采用普通二极管的续流回路相比,采用瞬变抑制二极管的续流电路能使电流的下降延迟时间缩短10倍以上.     

Comparison of a synergetic battery pack drive system to a pulsewidth modulated AC induction motor drive for an electric vehicle

A new battery configuration technique and accompanying control circuitry, termed a synergetic battery pack (SBP), is designed to work with lithium batteries, and can be used as both an inverter for an electric vehicle AC induction motor drive and as a battery charger. In this paper, the performance of a synergetic battery pack during motor drive operation is compared via computer simulation with a conventional motor drive which uses sinusoidal pulse width modulation (SPWM) to determine its effectiveness as a motor drive. The study showed that the drive efficiency was compatible with the conventional system, and offered a significant advantage in the lower frequency operating ranges. The voltage total harmonic distortion (THD) of the SBP was significantly lower than the PWM drive output, but the current THD was slightly higher due to the shape of the harmonic spectrum. In conclusion, the SBP is an effective alternative to a conventional drive, but the real advantage lies in its battery management capabilities and charger operation