三相并网逆变器LCL滤波器的简明设计

LCL滤波器以其较好的滤波性能被广泛地用于并网逆变器,但无阻尼时系统产生谐振,给系统的稳定性控制带来困难。文中在建立三相并网逆变器数学模型的基础上,采用基于d,q同步旋转坐标系的电网电压定向控制策略,利用被动阻尼抑制谐振提高了并网逆变器的稳定性能。文中给出了被动阻尼LCL滤波器的详细设计方法,并比较其与单L滤波器的滤波效果,运用Matlab/simulink建立系统模型并进行仿真,实现了单位功率因数并网。     

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。     

LCL滤波并网逆变器的控制策略

本文关于LCL滤波并网逆变器的控制研究,研究了最合适的关于LCL滤波并网逆变器的控制方案。在开关的频率保持在同一个水准的时候在一个开关的周期内,研究组进行了对于逆变器的多次采样研究,有效地减少了在数字技术下控制的延时情况,提高了系统中本来的控制范围与延时时间。在定量分析的方式下,小组中的研究人员已经证实的开展了对LCL滤波并网逆变器本质性能的研究,分析了它的优势性能。与常规有源阻尼多环结构相比,该方案采用电流单环控制即可实现系统稳定,无需增加传感器,从而简化了控制结构。在最后,研究人员也同时通过了实验来对LCL滤波并网逆变器的性能进行了验证分析。     

基于虚拟电阻法的LCL滤波器特性分析

LCL滤波器与传统的L滤波器相比,有着更好的滤波效果,但是,同时LCL滤波器会有谐振问题,导致了系统不稳定。为了要抑制其谐振特性,将虚拟电阻法和无源阻尼法这两种控制策略进行了研究分析,还将虚拟电阻法运用到了光伏并网逆变器中,最后通过仿真结果的对比,表明了虚拟电阻法可以有效地抑制LCL滤波器的谐振峰,降低了输出电流的谐波,系统的稳定性也得到了增强。     

一种基于LLCL型滤波器的光伏逆变器分析与设计

提出了新型并网逆变器的高阶功率滤波器的拓扑电路,称为LLCL滤波器。采用新型LLCL型滤波器对单相光伏并网逆变器进行滤波,LLCL滤波器通过在传统LCL滤波器的电容支路中串联一个小的电感达到在开关频率处产生串联谐振,相比LCL型滤波器能够更大程度地对串联谐振频率处的电流谐波进行衰减,可以减少电感装置的体积和重量,减少动态响应时间。更重要的是,能够减少电网侧的电感值,这样可以提高特征谐振频率点,有利于并网逆变器的控制。对比分析了传统LCL滤波器和LLCL滤波器的性能,证实和评估LLCL滤波器的优越性。对LLCL滤波器进行了参数设计,使用Matlab仿真软件搭建模型,仿真结果表明系统具有较好的稳态性能,且抗干扰性能好。     

基于广义积分器二自由度PID控制的LCL变流器

本文提出了一种基于广义积分器的LCL并网逆变器单电流反馈二自由度PID控制策略（Generalized Integrator based Two Degrees of Freedom PID Control Strategy,GI-2DoF-PID）,该方法不用增加电压或电流传感器就可实现有源阻尼控制,系统成本低。GI-2DoF-PID的比例积分环节实现并网电流跟踪,而基于广义积分器的微分环节则增强LCL逆变器的阻尼系数,有效抑制系统与电网形成的谐振尖峰,提高系统可靠性与稳定性,改善系统的动态响应速度。本文推导了GI-2DoF-PID电流控制系统的传递函数,分析了系统的稳定裕度与动态特性,提出相应的参数设计原则并选取了合适的控制参数。构建了基于PLECS系统仿真模型,仿真结果表明：GI-2DoF-PID控制的LCL并网逆变器可以有效抑制LCL滤波器谐振;在电网电压严重畸变时的满载并网电流畸变率仅为3%,远低于国家标准的要求;当系统从半载跳变到满载时,系统超调量低,响应速度比其他方法更快。     

基于LCL型并网逆变器的二自由度控制技术研究

并网逆变器的交流侧大多都采用LCL型滤波器对系统进行滤波,相比于L型滤波器它可以达到更好的滤波效果,然而,由于LCL型滤波器容易产生高频谐振,系统的稳定性会因此而受到影响。为了解决这个问题,提出了多种解决方案,其中无源阻尼和有源阻尼是使用比较广泛的两种控制方法。该文将一种二自由度PID控制策略应用于光伏并网逆变控制系统之中,通过Matlab仿真分析了系统的性能,实验结果表明,该方法增强了系统的鲁棒性和跟随性,对系统的谐波有较好的抑制效果。     

基于LCL滤波器的逆变器并网有源阻尼控制策略

目前LCL滤波器的逆变器广泛应用于并网过程中,由于本身是三阶欠阻尼系统,常常出现谐振尖峰,进而导致系统不稳定。对此,提出一种基于带通滤波器单反馈有源阻尼策略。首先,选取合适的LCL滤波器参数实现并网条件。其次,从幅值特性和相位裕度的角度出发,采用极点配置法对带通滤波器进行参数设计并设置反馈并网高频电流。最后,通过MATLAB/Simlink仿真验证带通滤波器有源阻尼方法的可行性和有效性。     

基于谐波频谱的LCL滤波器性能分析

为了减少逆变器中的谐波干扰,常采用LCL滤波器,该滤波器性能优良,被广泛采用,但目前LCL滤波器的电感电容仍然较大,系统成本仍较高,据此提出一种新型的设计方法,即通过逆变器输出的高次谐波峰值及其频谱,采用直线交截法依次获得谐振频率等相关滤波参数。与此同时,在此基础上对基于谐波频谱的LCL滤波器的各参数再次进行优化,然后通过与未经优化的LCL滤波器进行性能分析比较,从理论上揭示了该滤波器的优越性。最后通过在三相并网逆变器上进行实验验证,最终设计出了总电感电容较小,且满足并网要求的LCL滤波器。     

LCL型并网逆变器电流控制稳定性分析

在LCL型光伏并网逆变器中,电流控制器的比例控制系数设计不合理易造成系统不稳定,甚至损坏逆变器。对采用逆变侧电感电流反馈的LCL型三相光伏并网逆变器进行数学建模,运用Routh-Hurwitz稳定性判据基于系统离散化模型进行稳定性分析,可求得比例控制系数的精确范围。分析逆变侧电感、滤波电容以及网侧电感的取值与比例控制系数的关系,探讨滤波电感和电容的取值对系统稳定性的影响。通过Matlab仿真及在50 k W光伏逆变器实验平台上进行测试,验证了所进行的稳定性分析的正确性。     

Quasi-Z Source Inverter Control of PV Grid-Connected Based on Fuzzy PCI

The photovoltaic grid-connected inverter is an important interface between the photovoltaic power generation system and power grid. Its high-quality operation is directly related to the output power quality of the power grid. In order to further optimize the control effect of the quasi-Z source grid-connected photovoltaic inverter, a fuzzy proportional complex integral control (PCI) method is proposed for the current internal loop control. This method can eliminate the steady-state error, and has the characteristic of zero steady-state error adjustment for the AC disturbance signal of a specific frequency. The inductance-capacitance-inductance (LCL) filter is adopted in the grid-connected circuit, and the feedback capacitive current is taken as the control variable of the inner loop to form the active damping control method, which can not only effectively suppress the resonance of the LCL circuit, but also significantly inhibit the high-order harmonics in the grid-connected current. Finally, a system simulation model is built in MATLAB/Simulink to verify the superiority and effectiveness of the proposed method.     

Grid current regulation of a three-phase voltage source inverter with an LCL input filter

Many grid connected power electronic systems, such as STATCOMs, UPFCs, and distributed generation system interfaces, use a voltage source inverter (VSI) connected to the supply network through a filter. This filter, typically a series inductance, acts to reduce the switching harmonics entering the distribution network. An alternative filter is a LCL network, which can achieve reduced levels of harmonic distortion at lower switching frequencies and with less inductance, and therefore has potential benefits for higher power applications. However, systems incorporating LCL filters require more complex control strategies and are not commonly presented in literature. This paper proposes a robust strategy for regulating the grid current entering a distribution network from a three-phase VSI system connected via a LCL filter. The strategy integrates an outer loop grid current regulator with inner capacitor current regulation to stabilize the system. A synchronous frame PI current regulation strategy is used for the outer grid current control loop. Linear analysis, simulation, and experimental results are used to verify the stability of the control algorithm across a range of operating conditions. Finally, expressions for ""harmonic impedance" of the system are derived to study the effects of supply voltage distortion on the harmonic performance of the system.     

Digital Current Control of a Voltage Source Converter With Active Damping of LCL Resonance

Inductance–capacitor–inductance (LCL)-filters installed at converter outputs offer higher harmonic attenuation than L-filters, but careful design is required to damp LCL resonance, which can cause poorly damped oscillations and even instability. A new topology is presented for a discrete-time current controller which damps this resonance, combining deadbeat current control with optimal state-feedback pole assignment. By separating the state feedback gains into deadbeat and damping feedback loops, transient overcurrent protection is realizable while preserving the desired pole locations. Moreover, the controller is shown to be robust to parameter uncertainty in the grid inductance. Experimental tests verify that fast well-damped transient response and overcurrent protection is possible at low switching frequencies relative to the resonant frequency.     

A 6.6-kV transformerless shunt hybrid active filter for installation on a power distribution system

This paper presents a fully-digital-controlled shunt hybrid filter for damping of harmonic propagation in power distribution systems. The harmonic propagation is caused by resonance between line inductances and power capacitors installed for power factor correction. A possible solution to damping out harmonic propagation is based on installation of a shunt pure active filter at the end of a feeder. This paper proposes a shunt hybrid active filter characterized by series connection of a seventh-tuned LC filter per phase and a small-rated three-phase active filter. Like the pure filter, the hybrid filter is connected to the end bus of a feeder. The capacitor of the LC filter imposes a high impedance to the fundamental frequency, so that the fundamental voltage appears across the capacitor. This unique feature allows us to directly connect the hybrid filter to the 6.6-kV power line without step-down transformers. Furthermore, the capacitor used in this hybrid filter is lighter, cheaper and smaller than the transformer used in the pure filter. Theoretical analysis, along with experimental results obtained from a 200-V, 20-kW laboratory system, verifies the viability and effectiveness of the proposed hybrid filter.     

A hybrid active filter for damping of harmonic resonance inindustrial power systems

This paper proposes a hybrid active filter for the damping of harmonic resonance in industrial power systems. The hybrid filter consists of a small-rated active filter and a 5th-tuned passive filter. The active filter is characterized by detecting the 5th-harmonic current flowing into the passive filter. It is controlled in such a way as to behave as a negative or positive resistor by adjusting a feedback gain from a negative to positive value, and vice versa. The negative resistor presented by the active filter cancels a positive resistor inherent in the passive filter, so that the hybrid filter acts as an ideal passive filter with infinite quality factor. This significantly improves damping the harmonic resonance, compared with the passive filter used alone. Moreover, the active filter acts as a positive resistor to prevent an excessive harmonic current from flowing into the passive filter. Experimental results obtained from a 20-kW laboratory model verify the viability and effectiveness of the hybrid active filter proposed in this paper     

双馈风电变流器网侧LCL滤波器设计

本文提出了一种风电变流器网侧LCL滤波器设计方法。该方法在电流谐波脉动最大允许的条件下,选择总电感量;同时兼顾开关谐波电流衰减、基波无功约束条件、谐振频率约束条件,将总电感按一定的比例分为两部分,并选择合适的滤波电容。