直接驱动型风电系统谐波抑制技术研究

研究一种改进的直驱风电系统谐波抑制控制策略,针对电网电压畸变或不平衡引起的低次(5、7次等)电流谐波及负序分量,提出采用在同步坐标系下电流环PI调节器并联多谐振控制器的改进控制策略,以消除并网变流器电流谐波为目标,从而改善机组并网电能质量,同时也有效抑制功率波动。采用该改进谐波抑制控制策略无需进行复合坐标系下序列分解及谐波分离滤波器,不影响基波电流控制。实验结果表明:该控制策略可有效抑制谐波电流且易于实现数字控制,具有较好的实用价值。     

一种新颖的并联有源电力滤波器死区补偿方法

由于风电、光伏等分布式能源的电源开关器件采用半控或不控器件,以及控制器控制不精确等原因,给电网带来谐波、无功等影响。VSI型并联有源电力滤波器是一种可有效抑制谐波、无功的电力电子装置。在脉宽调制过程中,死区效应影响逆变器的非线性,使得常规控制方法下的APF对负载电流主要谐波存在跟踪误差。文章针对该死区效应问题提出一种新颖的电流前馈补偿方法。该方法不需要对参考电流进行极性判断,可有效降低控制器软件设计难度,同时可有效保证APF控制器的谐波电流跟踪响应特性。Matlab/Simulink仿真结果验证了该方法的正确性。     

基于分频控制的微电网储能变流器并网电能质量主动控制策略

阐述了基于锁相环误差补偿的谐波无功电流检测及多目标电流的生成方法,并提出一种基于分频控制的微电网并网电流电能质量主动提升控制策略,结合比例谐振(PR)控制器所具有的频率选址特性,实现了对特定次频率分量的零稳态误差控制,利用储能交流器(PCS)剩余容量快速并精确的选择性补偿谐波和无功电流,在此基础上,PCS模糊PR控制根据模糊规则表在线调整并整定了PR比例和积分参数,进而有效实现了对PCS的分频控制,提高了对电能质量治理的响应速度和控制精度,最后,搭建含储能装置的微电网并网运行平台开展相关实验测试,验证了所提控制策略的正确性和有效性。     

基于APF电动汽车充电站谐波放大效应及抑制措施

为提高电动汽车充电站并联有源滤波器的治理效果,文章研究有源滤波器在检测系统侧电流和负载侧电流两种控制方式下产生的谐波电流放大效应。搭建电动汽车充电机(站)的结构模型,分析充电站补偿系统等效电路,得到两种控制方式下充电站补偿系统谐波放大关系式和补偿效果。定义谐波放大程度系数、负载与系统间的阻抗比、APF治理因子等参数,提出抑制谐波放大效应措施。理论分析和算例仿真结果表明,所提方法能有效抑制谐波放大效应,提高APF补偿效率。     

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。     

LCL型滤波器在并联APF中的应用研究

针对L型滤波器应用于并联有源电力滤波器(APF)中的不足,建立了LCL型输出滤波器的数学模型,分析了APF系统采用LCL型滤波器的优越性;设计了基于LCL型输出滤波器的并联APF三环控制系统,在APF输出电流环的基础上引入电容电流内环,增大系统阻尼,保证系统的稳定性。通过MATLAB/simulink仿真验证了采用三环控制策略的LCL型APF系统能够对电网中的谐波电流实现精确跟踪和补偿,证明了控制策略的正确性和有效性。     

基于准比例谐振积分与重复控制的光伏并网逆变器研究

光伏逆变器并网控制策略的性能直接影响输出电能质量。文章针对谐振控制策略存在的不足,提出准比例谐振积分控制和重复控制的复合控制方法,准比例谐振控制器实现对基波正弦电流的无静差跟踪,重复控制器作为谐波补偿器抑制电网低次谐波,积分控制器消除低频直流的干扰,分析其稳态误差。仿真及实验结果表明,该控制方案能有效抑制谐波,具备良好的动态和稳态性能。     

自适应降阶广义积分STATCOM谐波补偿策略研究

为使静止同步补偿器(STATCOM)兼备无功电流补偿和指定次谐波电流补偿功能,提出基于降阶广义积分(reduced order generalized Integrator,ROGI)控制策略。该策略在静止坐标系下分离基波有功电流、谐波电流和无功电流,采用多个准ROGI谐振控制器对指定次谐波电流进行补偿控制。为避免准ROGI控制器容易受频率变化影响的缺陷,通过锁频环估算电网频率,主动修正ROGI谐振控制器频率与指定次谐波电流频率保持一致,提高电网频率变化时的电流补偿效果。该策略在静止坐标系下进行,无需锁相环和dq变化环节。搭建实验样机,对所提方法进行实验验证。结果表明该策略能有效补偿指定次谐波和无功电流,并对电网频率变化具有自适应性。     

基于输入输出反馈精确线性化的三相APF控制

将输入输出反馈精确线性化控制方法应用于三相有源电力滤波器非线性控制中。首先建立三相有源电力滤波器的仿射非线性系统模型,推导出了其输入输出反馈精确线性化非线性反馈控制律,实现三相并联型有源电力滤波器有功补偿电流和无功补偿电流的解耦控制器设计。最后使用Matlab进行仿真验证,仿真试验结果表明,该控制策略能较好地实现APF的解耦控制,具有较好的补偿特性,经该控制算法补偿,谐波畸变率限制在2%以下。     

四桥臂电压质量调节器及其在微电网中的应用

低压配电网电压跌落、骤升、不平衡、谐波等扰动影响微电网的正常并网运行,为抑制以上配电网电压扰动影响,采用具有综合补偿电压扰动能力的四桥臂电压质量调节器（VQR）。针对VQR的补偿目标,采用一种基于新型谐振PVPI控制器的电压电流双环控制策略,通过提取跌落后电压基波正序分量,将输出补偿量分为跌落（或骤升）补偿部分和用于抵消负序、零序及谐波电压分量部分,利用PVPI控制实现对两部分补偿指令信号的零稳态误差控制。仿真结果证明所提出的四桥臂电压质量调节器有效地补偿了配电网电压扰动的影响,提高了微电网故障穿越能力。     

并联型有源电力滤波器的Matlab仿真研究

有源电力滤波器用于动态谐波抑制和无功补偿,可以有效地改善电网质量,其主要由谐波电流检测和谐波补偿两部分组成。详细分析了并联型有源电力滤波器的结构及工作原理,采用基于瞬时无功功率理论的ip-iq谐波电流检测方法和三角载波电流跟踪控制方法,利用Matlab软件的Simulink模块对有源滤波器进行了系统建模,并进行了仿真研究。仿真结果表明,仿真模型能够实时检测系统中所含谐波电流,并进行补偿,可以很好地起到动态抑制电网谐波的效果。     

Power quality improvement using fuzzy logic controller for five-level shunt active power filter under distorted voltage conditions

In this paper, a five-level inverter is used as a shunt active power filter (APF), taking advantages of the multilevel inverter such as low harmonic distortion and reduced switching losses. It is used to compensate reactive power and eliminate harmonics drawn from a thyristor rectifier feeding an inductive load (RL) under distorted voltage conditions. The APF control strategy is based on the use of self-tuning filters (STF) for reference current generation and a fuzzy logic current controller. The use of STF instead of classical extraction filters allows extracting directly the voltage and current fundamental components in the α-β axis without phase locked loop (PLL). The MATLAB fuzzy logic toolbox is used for implementing the fuzzy logic control algorithm. The obtained results show that the proposed shunt APF controller has produced a sinusoidal supply current with low harmonic distortion and in phase with the line voltage.     

Unified power quality conditioner based on a three-level NPC inverter using fuzzy control techniques for all voltage disturbances compensation

This paper presents a novel and efficient control scheme for unified power quality conditioner (UPQC) based on three-level neutral point clamped (NPC) inverter using fuzzy logic techniques. The proposed UPQC is capable of mitigating source current harmonics and compensate all voltage disturbances such as voltage sags, swells, unbalances and harmonics. It is designed by the integration of series and shunt active filters (AFs) sharing a common DC bus capacitor. The DC voltage is maintained constant using proportional integral voltage controller. The synchronous reference frame (SRF) theory is used to get the reference signals for shunt active power filters (APFs) and the power reactive theory (p-q theory) for series APFs. The shunt and series APF reference signals derived from the control algorithm and sensed signals are injected in two controllers to generate switching signals. To improve the UPQC capability, fuzzy logic techniques are introduced to control the series APF. The performances of the proposed UPQC system are evaluated in terms of power factor correction, mitigation of voltage or current harmonics and all other voltage disturbances compensation using Matlab-Simulink software and SimPowerSystem toolbox. The simulation results illustrate the performance of the proposed UPQC at the common connection point of the nonlinear load to improve the power energy quality.     

单相并联有源电力滤波器延时补偿方案研究

在检测有源电力滤波器谐波电流、指令电流计算和基于PWM逆变电源的补偿电流输出过程中产生的有源电力滤波器延时对APF的补偿特性造成不利影响。为了保证有源电力滤波器具有良好的动态补偿性能,针对单相并联有源电力滤波器提出了基于ARMA(p,q)和LMS自适应滤波器的延时解决方案。通过MATLAB进行仿真验证,结果表明所提出的解决方案具有良好的补偿效果。     

具有APF功能的光伏并网发电系统的研究

探讨了一种具有有源滤波器功能的光伏并网发电系统。该系统白天可有效地进行光伏并网发电,还可补偿或抑制本地非线性负载产生的无功和谐波,夜晚系统仍可作为APF继续工作。相对于单独的光伏并网系统,它不但提高了设备利用率,也改善了电网的供电质量。文章分析了系统的结构组成,还采用了具有较好鲁棒性和动态响应速度的、基于瞬时无功理论的闭环无功和谐波电流检测的方法,分析了并网电流的合成及其跟踪控制。最后,利用Matlab/Simulink对系统进行了仿真,验证了系统的可行性。     

电力系统谐波、负序与无功电流复合补偿策略的研究

基于瞬时无功功率理论,提出了一种适用于三相三线制和三相四线制电力系统谐波、负序以及无功电流的复合补偿策略。数值仿真结果表明,该复合补偿策略的投入使用,可使电力系统综合补偿装置运行在有源电力滤波器和静止无功发生器功能相结合的复合工作模式,从而实现具有不对称非线性负载的电力系统的谐波抑制、无功补偿以及负载不平衡抑制等综合控制任务。     

Rapid transaction to load variations of active filter supplied by PV system

This paper deals with the analysis and control of a photovoltaic (PV) system connected to the main supply through a Boost converter and shunt active filter supplied by a PV system providing continuous supply of nonlinear load in variation. A robust control of a PV system connected to the grid while feeding a variable nonlinear load is developed and highlighted. This development is based on the control of the Boost converter to extract the maximum power from the PV system using the Perturb and Observe (P and O) algorithm in the presence of temperature and illumination. The proposed modeling and control strategy provide power to the variable nonlinear load and facilitates the transfer of power from solar panel to the grid while improving the quality of energy (harmonic currents compensation, power factor compensation and dc bus voltage regulation). Validation of the developed model and control strategy is conducted using power system simulator Sim-Power System Blockset Matlab/Simulink. To demonstrate the effectiveness of the shunt active filter to load changes, the method of instantaneous power (pq theory) is used to identify harmonic currents. The obtained results show an accurate extraction of harmonic currents and perfect compensation of both reactive power and harmonic currents with a lower THD and in accordance with the IEEE-519 standard.     

UPEC 2002 Preview

Using a shunt active power filter (SAPF) has been proved as an effective method to compensate reactive power and to mitigate harmonic currents of nonlinear loads. When designing a SAPF, it is crucial to generate reference currents for determining actual compensating current injections to the point of common coupling. In contrast to the conventional instantaneous reactive power theory, which needs coordinate transformations, the new method proposed in this letter is to determine reference compensating currents based on the balance of the instantaneous reactive and active power generated in the SAPF. It is shown that the proposed method is suitable for reactive and harmonic power compensation by using a SAPF In addition, to maintain the sinusoidal source currents this method also eliminates the need for installing energy storage devices for reactive power compensation as well as the DC source for the harmonic compensation in the active power filter. Therefore, a simpler design of the SAPF with minimal line losses can be expected.