Control strategies for harmonic mitigation and power factor correction using shunt active filter under various source voltage conditions

This paper gives a new insight into the concept of load compensation using shunt active filter (SAF) under ideal and non-ideal source voltage conditions. A novel approach based on an improved instantaneous active and reactive current component method is proposed. The performance of the proposed control strategy has been compared with instantaneous reactive power theory, symmetrical component theory and dq theory. SAF has been realized by three-phase voltage source converter. Reference currents generated by control strategies has been tracked by a SAF in a hysteresis band control scheme. The performance of the proposed scheme is evaluated in terms of reactive power compensation, reduction in magnitude of source currents, compensator currents, and harmonic compensation as per IEEE-519 standard. To ascertain the viability of the proposed control algorithm, the performance is evaluated under different source voltage conditions with the IEEE Standard-1459 power definitions. Variation in magnitude as well as harmonic content of source voltage has been considered. Under balanced sinusoidal source voltage condition, all control strategies congregate to similar results. Under unbalanced sinusoidal source voltage condition, dq theory and proposed theory have shown similar performance. However, under distorted source voltage conditions, an improved instantaneous active and reactive current component theory presents superior performance. A three-phase, three-wire distribution system supplying non-linear load is considered for simulation study. Simulation results from a complete model of SAF are presented to validate and compare the control strategies.     

四桥臂并联型有源电力滤波器控制研究

针对三相四线制电力系统谐波治理,提出了一种四桥臂并联型有源电力滤波器(SAPF)谐波补偿改进控制方案。谐波电流跟踪控制采用三维空间矢量调制算法,SVPWM具有直流电压利用率高、电流畸变率小等优点;直流侧总电压稳定,采用模糊PI自适应控制,直流侧电压动态响应快,超调小。对SAPF直流侧上下电容电压值平衡控制进行了研究。通过仿真验证了该控制方案的正确性与可行性。     

改进的并联型H桥APF控制策略研究

为了提高并联型H桥有源滤波器的工作效率，当电源电压失真时，更短的时间内计算出更精确的补偿电流，提出了一种自适应谐波检测算法和载波相移正弦脉冲宽度调制技术（CPS-SPWM）相结合的控制策略。首先通过自适应谐波检测算法快速准确地计算出参考补偿电流，为无差拍控制提供精确的补偿指令，然后采用外环电压PI控制实现桥臂电压稳定，并采用内环均压比例控制实现桥臂上子模块电容电压相同，最后通过CPS-SPWM为有源滤波器提供更准确的调制波信号。通过仿真结果，证明了改进的控制策略比传统方法具有更高的稳定性和准确率。     

神经网络控制的三相并联有源电力滤波器设计

针对现有各种谐波检测方法的不足,在分析了滤波器的工作原理和传统的神经网络控制算法之后,提出了一种新的神经网络控制算法,设计了一种应用于电力系统中补偿无功和抑制谐波的三相并联有源电力滤波器(APF),该滤波器由一个三相PWM电压源逆变器及其控制电路组成。将负载电流、直流侧电容电压与系统电压输入改进的神经网络,计算出并联有源电力滤波器的参考电流,参考电流输入滞环电流控制器获得逆变器的触发脉冲,从而得到补偿电流。通过Matlab仿真表明,由改进的神经网络控制的滤波器,在负载变化及其电流变化情况下都有良好的性能。同时,通过数字信号处理器实现的系统实验验证了该方案的正确性。     

Modeling and controller synthesis for the cascaded H-bridge multilevel active power filter with ADALINE-based identifiers

This paper presents the averaged state-space modeling and controller synthesis methodology for the cascaded H-bridge multilevel active power filters (CHB-APFs). The accurate harmonic current compensation and dc-link stabilization among the individual H-bridge modules are crucial problems for the CHB-APF, which is the prerequisite for the global stability of the system. In this study, a novel voltage balancing algorithm is devised by splitting the dc-link control task into two parts, namely, the average voltage control and the voltage balancing control, where the sine and cosine functions of the phase angle of the fundamental grid voltage are used, respectively. To ensure accurate phase tracking, a novel phase-locked loop algorithm is proposed by using the adaptive linear neural network (ADALINE). Moreover, a separate ADALINE identifier is applied for reference current generation, and the proportional-resonant controller is used for current tracking. The simulation results obtained from the Alternative Transient Program (ATP/EMTP) are provided under dynamic reactive power compensation and active filtering scenarios. The experimental results from the prototype system are also presented, which verifies the effectiveness of the devised algorithms.     

适用于双馈风电系统的九开关型统一电能质量调节器

为减小电压谐波、电压跌落与骤升、电压不平衡等电能质量问题对双馈感应发电机(DFIG)风电系统的影响,在对多种统一电能质量调节器(UPQC)拓扑结构研究对比和九开关变换器建模分析的基础上,提出一种应用于双馈风电系统的九开关型UPQC方案。在对UPQC电压、电流补偿单元运算电路建模的基础上,设计相应的控制策略。按照电网工况,设定谐波电流补偿、轻度电压补偿、重度电压补偿3种工作模式,优化UPQC运行方案。仿真与实验结果表明,九开关型UPQC可以有效治理电压、电流谐波,消除电压偏差与相位跳变,提高DFIG机端电能质量,使机组可以在多种故障电压工况下实现柔性故障穿越。     

New Control Algorithm for Single-Phase Series Active Power Filter

This article presents a single-phase series active power filter for mitigation of the load voltage harmonic content while maintaining the voltage on the DC side regulated without the support of a voltage source. The proposed series active power filter control algorithm eliminates the additional voltage source to regulate the DC voltage, and with the adopted topology, a coupling transformer is not used to interface the series active power filter with the electrical power grid. The article describes the control strategy that encapsulates the grid synchronization scheme, compensation voltage calculation, damping algorithm, and dead-time compensation. The topology and control strategy of the series active power filter have been evaluated in simulation software, and simulations results are presented. Experimental results, obtained with a developed laboratorial prototype, validate the theoretical assumptions and are within the harmonic spectrum limits imposed by the international recommendations of IEEE Standard 519.     

适用于飞机电网的并联型有源电力滤波器功率电路及其控制策略

针对飞机电网频率较高、电源内阻抗较大的特点,采用并联型有源电力滤波器实现对电网谐波的集中抑制。采用改进的交叉矢量算法实现对基准补偿电流的检测和计算,采用滞环电流控制实现对较高频率电源系统瞬时电流的补偿,同时对直流侧电压进行稳压调节,并推导其传递函数。仿真和实验结果验证了将APF应用于飞机电网的正确性和可行性,表明采用本文的有源滤波器可集中抑制电网谐波电流,具有较好的补偿效果。     

单独注入式混合型有源电力滤波器复合控制策略的研究

本文建立了单独注入式混合型有源电力滤波器的电气模型。根据此模型综合比较了混合型有源电力滤波器的两种常用控制策略,提出了一种基于检测电网谐波电压与谐波电流的混合有源电力滤波器复合控制方案,并对其补偿性能和抑制电网频率和系统阻抗变化的影响进行了分析。为了实现系统的无差控制,提出了基于递推积分的PI算法,并且由模糊推理在线整定比例系数和积分系数,该算法能有效地提高系统的动态和稳态性能。仿真和实验结果表明采用这种复合控制的注入式混合有源电力滤波器能达到较好的滤波效果。     

预测控制三电平并联型有源电力滤波器系统

针对三电平并联型有源电力滤波器数控系统存在采样、计算等引起的固有延时及直流侧电压存在波动问题,提出了一种将直流侧电压模糊PI自整定控制、谐波电流预测控制和三电平电压空间矢量脉宽调制算法相结合的基于三电平SAPF数字模型等双闭环控制方案。仿真试验验证了该系统具有良好的谐波补偿性能和应用价值。     

A novel approach of reference current generation for power quality improvement in three-phase, three-wire distribution system using DSTATCOM

This paper presents a novel approach based on an improved instantaneous active and reactive current component theory for generating reference currents for distribution static compensator (DSTATCOM). Three-phase reference current waveforms generated by proposed scheme are tracked by the three-phase voltage source converter in a hysteresis band control scheme. The performance of the DSTATCOM using the proposed control strategy has been evaluated under various source and load conditions. The performance of the proposed control strategy has been evaluated in terms of load balancing, reactive power compensation, compensator rating and harmonic mitigation. A three-phase, three-wire distribution system supplying star connected linear as well as non-linear unbalanced load is considered for simulation study. The detailed simulation results using MATLAB/SIMULINK software are presented to support the feasibility of proposed control strategy.     

改进多通道注入式HAPF与TCR联合系统

针对多通道注入式混合有源电力滤波器(HAPF)无法动态补偿无功功率的问题,在对比两种不同结构多通道注入式HAPF的基础上,提出一种改进多通道注入式HAPF与晶闸管控制电抗器(TCR)联合运行系统,实现中高压配电网谐波与无功的综合动态治理.在提出的谐波电流分频控制方法中,采用改进的ip-iq算法对电网中的各次谐波进行分频检测,各次谐波电流在注入电网过程中产生的相角偏移可在相应的sin - cos函数表中进行校正,直流侧电压实时值与给定值的误差通过PI控制后送入有功通道经d-q变换转化为三相交流值后与谐波电流控制信号叠加形成最终的控制信号.仿真及实验结果证明了所提出的控制方法的有效性.     

基于级联有源滤波器与静止无功补偿器的综合补偿控制方案

级联多电平有源滤波器(CS-APF)与静止无功补偿器(SVC)同时运行存在稳定性及无功补偿控制优化等问题。文中提出一种统一控制策略,结合SVC和CS-APF的功能特点,使SVC对负载正序无功分量及负序分量的补偿进行前馈控制和电网电纳(不包含CS-APF分量)反馈控制;CS-APF对晶闸管相控电抗器(TCR)与电网负载谐波的补偿进行前馈控制,并去除SVC中固定电容分量,进行电网电流反馈控制,同时对SVC无功补偿进行二次优化补偿。另外,提出一种TCR谐波电流预计算方法,根据TCR触发角当前值与电网电压锁相环相位,构建TCR谐波电流,实现对TCR谐波的预计算。仿真和实验研究表明,在该综合控制方案下,SVC与CS-APF控制不存在闭环,系统稳定性高,TCR谐波补偿无滞后,无功补偿响应较快,补偿能力强。     

滑窗迭代DFT法APF直流侧稳压控制研究

有源电力滤波器(APF)是抑制电网谐波的新型方法,其补偿性能主要取决于谐波检测环节和控制环节,同时直流侧稳压控制是APF正常工作的前提。引入滑窗迭代DFT谐波电流检测方法;提出一种稳压电流各相均分的直流电压控制策略;从功率平衡的角度分析了电压环PI调节器参数设计方法。建立仿真模型及设计实验样机,仿真和实验均验证了滑窗迭代DFT法谐波检测的快速性和精确性,以及所提直流侧稳压控制策略的正确性。     

双馈风力发电系统的比例谐振直接电压控制

提出双馈异步发电机的比例谐振直接电压控制策略,实现双馈风力发电系统的电网同步控制。通过分析双馈异步发电机的数学模型,建立了转子旋转坐标系中转子电压对定子电压的直接控制关系。在转子旋转坐标系中采用比例谐振控制器控制定子电压,以实现对交流电网电压的无静差跟踪。与传统双馈异步发电机的电网同步控制策略相比,提出的控制策略减少了坐标旋转变换的次数,消除了转子电流的测量和控制环节,避免采用受发电机参数影响的前馈补偿控制,从而简化了控制算法,提高了控制系统的鲁棒性。仿真结果表明,提出的控制策略可有效地实现双馈异步发电机的电网同步控制。     

混合有源电力滤波器的新型电流迭代学习控制

混合有源电力滤波器可以动态抑制电网谐波电流和补偿容性无功功率,改善电网电能质量。针对传统PI型迭代学习控制算法在并联有源电力滤波器应用中的不足,算法收敛性严重依赖于学习控制的初始输入,迭代学习控制器的参数是定常值,会影响有源滤波系统的控制性能。本文提出一种新型PI迭代学习控制算法,将其应用于混合有源电力滤波器系统的电流反馈控制中,得到了应用迭代算法的收敛性条件,并采用一种改进的Ziegler-Nichols方法对控制器参数进行了优化,以提高系统的控制精度。为了提高系统的动态响应性能,提出一种谐波电流误差的反馈-前馈控制策略,其中电流误差信号的D型前馈控制环节用于实现滤波器系统的电流快速补偿,同时利用一个三层BP神经网络对前馈控制增益进行优化。仿真和实验结果证明了该迭代算法及控制策略的可行性与有效性。     

具有谐波抑制功能的电网电能质量最优控制方法

电网运行过程中容易受谐波干扰,造成电压畸变、网损过度.为此,提出具有谐波抑制功能的电网电能质量最优控制方法,优化电网电能质量的同时有效抑制谐波干扰.采用分层控制策略,初级控制采用多目标电压无功谐波优化算法获取电压差异数据、电压不稳定性数据、网络损坏率数据、电网谐波数据优化电网电压输出,同时采用模糊PI控制器完成复合电流...     

基于虚阻尼控制的T-SAPF滤波系统谐振抑制研究

为了降低整流桥、变频器等强非线性负载向电网引入的谐波污染,提出一种由并联型有源电力滤波器(SAPF)与晶闸管投切滤波器(TSF)构成的T-SAPF混合滤波系统。针对TSF可能与电网发生并联谐振的问题,在对谐振机理进行分析的基础上,提出一种可以抑制系统并联谐振的SAPF虚阻尼控制策略,将自调谐滤波算法应用于阻尼电流指令的提取,并根据三个约束条件来界定阻尼系数的有效值域。仿真结果表明,该虚阻尼控制策略能够有效抑制系统的并联谐振,降低谐振时PCC电压的畸变程度,同时保证谐波电流的补偿效果。     

Network conditioners on the basis of active filters

A novel control scheme for the stabilization of load voltage and the compensation for high harmonics of load current in series-type active power filter systems combined with shunt-type active power filters is proposed. The control system allows an effective correction of power factor, harmonic distortion, and load voltage regulation.     

Harmonic estimation using RLS algorithm and elimination with improved current control technique based SAPF in a distribution network

This paper presents the application of well known recursive least square (RLS) harmonic estimation technique and its elimination with improved current control technique based shunt active power filter (SAPF) in a distorted power network. The estimation of amplitude and phase angle of fundamental and harmonics is performed using RLS algorithm, known for their simplicity of computation, accuracy and good convergence properties. The estimates are updated recursively as samples of the harmonic signals are received. In order to eliminate harmonics produced by the nonlinear load connected in the distribution network, a three-phase SAPF with modified current control technique is employed. In this paper, based on the analysis and modeling of SAPF with closed-loop control, a feed forward compensation path of load current and a new pulse width modulation (PWM) control scheme is proposed to improve the dynamic performance of the SAPF. In this case the amplitude and phase angle of the converter AC voltage should be adjusted using PWM, thus producing either leading or lagging reactive power. Harmonic contented in the signal is estimated at the point of common coupling (PCC) with and without SAPF. The comparative results of amplitude and phase angle of fundamental and selected harmonics are determined considering installation of SAPF in the distribution network. The system is studied using MATLAB environment to justify the effectiveness of proposed control technique in comparison to the other techniques discussed in the recent literature.