电力有源滤波器在供电系统中的应用（续）

电力有源滤波器在供电系统中的主要应用是补偿电网中的谐波和无功功率,依此改善交流电源的供电质量。文中介绍了电力有源滤波器的电路结构以及控制方式。给出了电压型电力有源滤波器、电流型电力有源滤波器、多模式电力有源滤波器以及混合型电力有源滤波器的电路结构,并重点介绍无功电流和谐波电流的检测、逆变器直流侧电源电压的控制以及混合型电力有源滤波器的控制方案,最后给出了电力有源滤波器的补偿特性。     

电力有源滤波器在供电系统中的应用

电力有源滤波器在供电系统中的主要应用是补偿电网中的谐波和无功功率,依此改善交流电源的供电质量。文中介绍了电力有源滤波器的电路结构以及控制方式。给出了电压型电力有源滤波器,电流型电力有源滤波器,多模式电力有源滤波器以及混合型电力有源滤波器的电路结构,并重点介绍无功电流和谐波电流的检测,逆变器直流侧电源电压的控制以及混合型电力有源滤波器的控制方案,最后给出了电力有源滤波器的补偿特性。     

功率因数校正技术及不同控制策略研究

功率因数校正电路广泛应用于交-直电源变换电路中,以消除电力系统的谐波,提高功率因数。为此,对典型的有源PFC的Boost电路进行原理性分析,并对有源功率因数校正的各种控制方法从不同角度进行分析和比较,如连续导通模式、不连续导通模式和临界导通模式,平均电流模式、电流峰值模式和电流滞环控制等。最后以L6561为例说明各种功率因数控制方法不是独立而是相互联系的,实际应用中应该结合考虑各方面具体情况来进行选择。     

基于比例谐振控制的单相并网逆变器偏移误差分析与抑制

在单相并网逆变器中,电流传感器、不平衡电压和元器件的非线性特性都会导致相电流出现偏移误差。当包含偏移误差的相电流用于电流控制时,会直接导致直流侧(DC)出现偏移,网侧电流出现二次谐波分量。DC偏移量和二次谐波分量会降低并网逆变器的效率。本文提出了一种基于比例谐振(PR)控制的单相并网逆变器偏移误差补偿算法,并通过仿真验证了该算法的有效性。     

2kW有源功率因数校正电路设计

有源功率因数校正可减少用电设备对电网的谐波污染,提高电器设备输入端的功率因数。详细分析有源功率因数校正APFC(active power factor corrector)原理,采用平均电流控制模式控制原理,设计一种2 kW有源功率因数校正电路。实验结果表明:以TDA16888为核心的有源功率因数校正器能在90～270 V的宽电压输入范围内得到稳定的380 V直流电压输出,功率因数达0.99,系统性能优越。     

开关电源的有源功率因数校正电路设计

有源功率因数校正可减少用电设备对电网的谐波污染,提高电器设备输入端的功率因数。详细分析了有源功率因数校正APFC(active power factor corrector)原理,采用平均电流控制模式控制原理,设计了基于UC3854BN芯片的一种有源功率因数校正电路方案,着重分析了电路主要参数的选择和设计。实践证明,采用APFC后,大大减小了输入电流的谐波分量,实现了功率因数校正。     

2 kW有源功率因数校正电路设计

有源功率因数校正可减少用电设备对电网的谐波污染,提高电器设备输入端的功率因数.详细分析有源功率因数校正APFC(active power factor corrector)原理,采用平均电流控制模式控制原理,设计一种2 kW有源功率因数校正电路.实验结果表明:以TDA16888为核心的有源功率因数校正器能在90～270V的宽电压输入范围内得到稳定的380V直流电压输出,功率因数达0.99,系统性能优越.     

并联型有源电力滤波器直流侧电压柔性控制策略

针对并联型有源电力滤波器的直流侧电压控制特点,提出了一种对直流侧电压进行柔性控制的并联型有源电力滤波器控制策略。该策略中,在直流侧电压控制部分引入反馈低通滤波器,削弱直流侧固有谐波对输出电流控制的影响;在电流控制的输出部分通过增加直流侧电压前馈系数,抵制在变换桥中可能引入的直流侧电压谐波影响。仿真结果表明直流侧电压柔性控制策略能够降低APF系统补偿后的电源电流总谐波畸变率,从而改善并联型有源电力滤波器的谐波补偿性能。     

基于DSP控制的可再生能源并网逆变器的设计

随着环境污染、能源短缺问题的日益突出,发展可再生能源发电已成为一种必然趋势,而并网变流器是光伏发电、风力发电等可再生能源发电并网的关键设备。文中主要对新能源并网变流器的网侧逆变器进行了研究,获得了三相PWM网侧逆变器的拓扑结构,确定了网侧逆变器的控制策略,并设计了电压、电流PI控制器。为了验证文中提出的控制策略的正确性,采用TMS320F2812 DSP作为控制芯片,研制了一台20kW并网变流器的样机,并进行了相关实验研究,试验结果表明并网电流可以正弦化,系统可以实现单位功率因数运行,具有优良的并网性能。     

一种基于有源滤波与光伏发电的并网逆变器控制方法

文中提出了一种基于有源滤波与光伏发电的并网逆变器的控制方法,在并联型有源电力滤波器的基础上拓展了新能源发电功能,采用电压电流双环对并网逆变直流侧电压和系统电网输出有功电流进行控制。该并网逆变器既可以滤除负载的谐波和补偿负载的无功功率,也可以实现有功功率的有效传输,适于未来微电网中并网逆变器的应用研究。     

基于电网电压矢量定向的三相并网逆变系统设计

本文介绍了并网逆变用LCL输出滤波器的设计步骤和基干电网电压矢量定向的并网逆变系统直接电流控制方案的基本原理与推导过程,利用数字信号处理器TMS320F2812设计了一台原理样机。仿真和实验结果表明：网侧电流比逆变器侧电流高次谐波得到更好地衰减,并网电流与电网电压保持同相位,系统以单位功率因数向电网馈送电能。     

新能源并网逆变器入网电流通用控制

太阳能电池、风力发电,以及燃料电池等新能源发电中的并网逆变器技术的研究已经成为一个重要的研究方向。为了消除逆变器输出电流中的高次谐波,通常采用LCL滤波器对谐波进行处理。但是LCL滤波器是无阻尼三阶系统,使输出容易产生谐振,因此逆变器电流控制器的研究成为了研究的热点。本文就当今使用较为热门的电容电流内环、入网电流外环的双闭环控制策略进行分析,使用MATLAB／Simulink进行仿真,并在仿真中加入功率因数（PF）的验证。从仿真结果看出该方案可有效地避免入网电流谐振,入网电流能很好地跟踪并网电压,达到同频同相,功率因数约等于1,并且在FFT谐波分析中达到满意的效果。     

Enhanced power quality based single phase photovoltaic distributed generation system

This article presents a novel control strategy for a 1-? 2-level grid-tie photovoltaic (PV) inverter to enhance the power quality (PQ) of a PV distributed generation (PVDG) system. The objective is to obtain the maximum benefits from the grid-tie PV inverter by introducing current harmonics as well as reactive power compensation schemes in its control strategy, thereby controlling the PV inverter to achieve multiple functions in the PVDG system such as: (1) active power flow control between the PV inverter and the grid, (2) reactive power compensation, and (3) grid current harmonics compensation. A PQ enhancement controller (PQEC) has been designed to achieve the aforementioned objectives. The issue of underutilisation of the PV inverter in nighttime has also been addressed in this article and for the optimal use of the system; the PV inverter is used as a shunt active power filter in nighttime. A prototype model of the proposed system is developed in the laboratory, to validate the effectiveness of the control scheme, and is tested with the help of the dSPACE DS1104 platform.     

有源前端型三电平逆变器中点电位平衡的一种控制策略

由三电平有源前端(AFE)和三电平逆变器构成的中高压变频器在能量再生,功率因数,输入和输出谐波方面具有良好的性能.在这种变频器中,为了实现直流侧中点电位平衡控制(NPB),以往的方法都要对逆变控制采用的SVPWM算法进行调整,这不可避免地会增加逆变输出谐波.本文提出一种无需调整SVPWM算法而只在变频器前端解决NPB问题的策略,避免了逆变输出谐波的增加,使负载电机旋转磁场具有较为理想的圆度.文中介绍了这种NPB的基本原理,对在前端控制与在逆变侧控制的输入和输出性能进行了比较分析.仿真实验研究结果证明了该控制策略的正确性和有效性.     

连铸坯视觉定重线结构光平面调整方法研究

鉴于传统三电平逆变电路存在谐波含量高的缺点, 在分析模块化多电平换流器(MMC)工作原理的基础上, 提出使用模块化多电平电路实现光伏并网逆变功能, 采用微分-跟踪器法实现光伏阵列最大功率点跟踪(MPPT)及逆变器PQ解耦控制, 实现了光伏系统以单位功率因数并网。在PSCAD中建立光伏并网系统动态仿真模型, 仿真结果表明, 所建模型具有开关损耗低、谐波量小的优点, 验证了所提方法的正确性和可行性。     

Harmonic analysis and performance improvement of slip energyrecovery induction motor drives

Slip energy recovery induction motor drives are used in high power applications, in which by controlling the slip power a variable speed drive system is provided. However, poor power factor is a disadvantage of the system. Presence of sub-harmonics of the line frequency on the stator side is one of the special features of these drives. A phase-controlled inverter can absorb the reactive power from the supply and inject the low-order current harmonics with relatively high amplitudes to the supply. This paper simulates the harmonic content of waveforms in various points of drive at different speeds, based on the hybrid model (dqabc). Then the sinusoidal pulse-width-modulation (SPWM) control technique is used in order to improve the power factor of the drive and to weaken the injected low-order harmonics to the supply. Based on the frequency spectrum, total harmonic distortion, distortion factor and power factor, two phase control and SPWM techniques are compared and the advantage of the SPWM technique over the phase control technique is shown     

Input Current Harmonics in a Regenerative Multicell Inverter With Single-Phase PWM Rectifiers

Harmonics are a very important issue in the design and operation of medium-voltage inverter drives, due to restrictions imposed by regulations. This paper studies the harmonics generated by a three-phase multicell cascade inverter, with single-phase pulsewidth modulation rectifiers at the input side of each cell; thus, the entire topology is able to regenerate power to the net. This paper identifies accurately the harmonic generation process in the dc-link voltage, the input current of each cell, and, therefore, at the input side of the inverter. Moreover, this paper proposes a method to reduce and, in some cases, eliminate the input current harmonics, reaching a very high input power factor for any operation condition. Simulation and experimental results are provided to validate the theoretical analysis.      

单相光伏逆变器的改进型并网控制方法

单相光伏并网逆变器通常采用双闭环控制和电网电压前馈控制的策略,其中双闭环的外电压环为采用PI恒压控制逆变前直流侧电压,分析比较了准比例谐振调节和PI调节两种电流内环的输出外特性,通过对电流内环采用准比例谐振控制的控制系统进行分析建模,建立了逆变器的单相并网仿真模型。仿真结果显示电流内环采用准比例谐振控制能实现并网电流的无静态误差控制,并减小电网频率偏移对并网电流的影响。仿真及实验得到的输出正弦电流波形良好,基于该并网控制策略的光伏逆变器能以高功率因数向电网发电,动态响应快、鲁棒性强、跟踪精度高、并网电流的THD明显优于传统方法,从而验证了改进后模型的可行性和实用性。     

A novel control scheme for the multilevel rectifier/inverter

A novel three-level pulsewidth modulation (PWM) rectifier/inverter is proposed: this single-phase three-level rectifier with power factor correction and current harmonic reduction is proposed to improve power quality. A three-phase three-level neutral point clamped (NPC) inverter is adopted to reduce the harmonic content of the inverter output voltages and currents. In the adopted rectifier, a switching mode rectifier with two AC power switches is adopted to draw a sinusoidal line current in phase with mains voltage. The switching functions of the power switches are based on a look-up table. To achieve a balanced DC-link capacitor voltage, a capacitor voltage compensator is employed. In the NPC inverter, the three-level PWM techniques based on the sine-triangle PWM and space vector modulation are used to reduce the voltage harmonics and to drive an induction motor. The advantages of the adopted th-ree-level rectifier/inverter are (1) the blocking voltage of power devices (T1, T2, S_a1-S_c4) is clamped to half of the DC-link voltage, (2) low conduction loss with low conduction resistance due to low voltage stress, (3) low electromagnetic interference, and (4) low voltage harmonics in the inverter output. Based on the proposed control strategy, the rectifier can draw a high power factor line current and achieve two balance capacitor voltages. The current harmonics generated from the adopted rectifier can meet the international requirements. Finally, the proposed control algorithm is illustrated through experimental results based on the laboratory prototype.     

Z-source inverter for motor drives

This paper presents a Z-source inverter system and control for general-purpose motor drives. The Z-source inverter system employs a unique LC network in the dc link and a small capacitor on the ac side of the diode front end. By controlling the shoot-through duty cycle, the Z-source can produce any desired output ac voltage, even greater than the line voltage. As a result, the new Z-source inverter system provides ride-through capability during voltage sags, reduces line harmonics, improves power factor and reliability, and extends output voltage range. Analysis, simulation, and experimental results will be presented to demonstrate these new features.