Three-Level Inverter-Based Shunt Active Power Filter in Three-Phase Three-Wire and Four-Wire Systems

This paper presents a direct current-space-vector control of an active power filter (APF) based on a three-level neutral-point-clamped (NPC) voltage-source inverter. The proposed method indirectly generates the compensation current reference by using an equivalent conductance of the fundamental component using APF's dc-link voltage control. The proposed control can selectively choose harmonic current components by real-time fast Fourier transform to generate the compensation current. The compensation current is represented in a rotating coordinate system with chosen switching states from a switching table implemented in a field-programmable gate array. In addition, a three-phase four-wire APF based on a three-level neutral-point-clamped inverter is also presented. The proposed APF eliminates harmonics in all three phases as well as the neutral current. A three-phase three-wire NPC inverter system can be used as a three-phase four-wire system since the split dc capacitors provide a neutral connection. To regulate and balance the split dc-capacitor voltages, a new control method using a sign cubical hysteresis controller is proposed. The characteristics of the APF system with an LCL-ripple filter are investigated and compared with traditional current control strategies to evaluate the inherent advantages. The simulation and experimental results validated the feasibility of the proposed APF.      

一种新型并联混合有源滤波器的研究

本文提出了一种新型并联混合型有源滤波器的拓扑，新型拓扑通并联谐 振抑制流过无源网络的基波无功电流，减小了有源滤波器承担的基波电流。同时在此拓扑基础上讨论了它的控制策略，在此控制策略下，有源滤波器不承担基波电矿井，且只承担很小的基波电流，因此有源滤波器的容量达到了最小，本文分析了并联谐振对无源网络阻抗的影响，并对此分析了控制策略在传统拓扑和新型拓扑下对有源滤波器容量的影响，最后通过仿真证明了结论的正确性。     

Direct Power Control of Active Filters With Averaged Switching Frequency Regulation

This paper has developed a direct power control (DPC) structure to improve the performance of an active filter. A control algorithm directly uses the instantaneous power terms as control variables to replace the current and voltage variables that are commonly used in proportional-integral (PI) control systems. Compared to the other DPC schemes that have been reported so far, the proposed algorithm is oriented to harmonic current compensation, for which the switching functions are redefined, the bandwidths of the two hysteresis comparators are dynamically adjusted, and consequently, the pulsewidth modulation (PWM) switching frequencies are regulated to eliminate the unnecessary short switching pulses, and the control system can be used directly and effectively for various types of nonlinear load compensation. With the proposed control scheme, full control of the active filter, including the line current and the dc bus voltage, can be realized within an integrated power control loop. The advantages of the proposed control strategy have been verified by simulation and experimental results on a 2-kVA laboratory prototype.      

Real-Time Estimation of Fundamental Frequency and Harmonics for Active Shunt Power Filters in Aircraft Electrical Systems

A novel algorithm for fundamental frequency and harmonic components detection is presented in this paper. The technique is based on a real-time implementation of discrete Fourier transform, and it allows fast and accurate estimation of fundamental frequency and harmonics of a distorted signal with variable fundamental frequency. It is suitable for active shunt filter applications, when fast and accurate tracking of the reference signal is required to achieve a good control performance. The main application for the algorithm is aircraft ac power systems, where the fundamental frequency can be either fixed on 400 Hz and its actual value fluctuates around the nominal value, or variable in the range 360–900 Hz. Hence, a real-time estimation of fundamental frequency is essential for active filter control. The proposed algorithm has been at first implemented in Matlab/Simulink for computer simulation, and it has been compared with a Phase Locked Loop (PLL) algorithm for frequency detection and the synchronous $dq$ reference method for harmonic detection. Experimental tests have been carried out in order to validate the simulation results. The distorted current absorbed by a nonlinear load is analyzed and processed by means of a digital implementation of the algorithm running on the active shunt power filter control DSP, in order to calculate the active filter compensating current.      

A Recursive Park Transformation to Improve the Performance of Synchronous Reference Frame Controllers in Shunt Active Power Filters

Load harmonic currents and load unbalances reduce power quality (PQ) supplied by electrical networks. Shunt active power filters (SAPFs) are a well-known solution that can be employed to enhance electrical PQ by injecting a compensation current at the point of common coupling (PCC) of the SAPF, the load, and the electrical grid. Hence, SAPF controllers must determine the instantaneous values of the compensation reference current, including nondesirable components of the load current. A family of SAPF controllers, which evaluates the compensation reference current using synchronous rotating frames (SRFs), employs a structure based on Park transformations: direct transform, low-pass filtering (LPF), and inverse transform. The cutoff frequency and the filter order of the LPF stage must be designed properly in order to obtain an accurate reference current and a fast dynamic response of these SAPF controllers. This paper proposes a recursive implementation of the direct Park transformation that avoids the filtering stage and allows accurate SRF controllers to be designed. Moreover, the proposed implementation is not dependent on PCC conditions. The proposed implementation is evaluated using a three-phase, three-wire SAPF and compared with LPF-based controllers by simulation and experiment.      

风电并网逆变器用有无功功率解耦控制的矢量控制策略

三相PWM逆变器是风力发电并网系统的主要部分,开发一种高性能的逆变器控制策略已经成为研究的重点。本文在对风力发电并网逆变器系统数学模型分析的基础上,提出了一种改进的矢量控制策略。它主要由两个双环控制模型构成,分别都是电流外环电压内环的结构。通过实时检测并网电流和电网电压的波动,有效的补偿并网电感的电压信号,就能够很好的补偿逆变器PWM调制波信号。本文提出的这种矢量控制结构不仅可以改善并网电流的波形质量,而且在系统给定参数发生变化的情况下,仍然可使系统具有很强的鲁棒性,此外,该结构还能有效补偿直流侧母线电压的脉动对并网电流质量的影响。     

大容量并联型有源电力滤波器的软启动技术

分析大容量并联型有源电力滤波器的系统模型和工作特点的基础上,提出了大容量并联型有源电力滤波器软启动的方法。电流环软启动通过输出电流指令递增实现,电压环软启动则比较了直流侧电压指令逐步升高法、恒定电流充电法、变PI参数调节法三种策略。实验结果表明并联型有源电力滤波器投入电网时直流侧电压上升平稳无超调,输出电流也无冲击现象,证明此软启动方法是有效的。     

基于三相并联混合有源滤波器的直接功率控制理论

文中研究的目的是使并联混合型有源电力滤波器取得更好的性价比。由于大功率的电力电子器件（GTO／IGCT）不能应用在高于10kHz,电流控制综合使用了同步参考坐标（SRF）和瞬时无功功率（IRP）的直接功率控制方法,而且IRP的矢量算法没有使用变换矩阵。这种方法的可行性用MATLAB的仿真结果得以证实。     

并联型三相有源滤波器谐波电流检测研究

在有源滤波器设计中,谐波电流的实时检测与分离是其中的关键环节。文中分析了基于瞬时无功理论的ip、iq法检测谐波电流的基本原理与实现方法。ipi、q法与DFT谐波电流检测方法相比,实时性能更好,容易实现,而且不受电网电压波形畸变的影响。仿真和实验表明,采用ipi、q法能够实时、准确地检测出非线性负载的谐波电流和无功电流。     

Seven-Level Shunt Active Power Filter for High-Power Drive Systems

In high-power adjustable-speed motor drives, such as those used in electric ship propulsion systems, active filters provide a viable solution to mitigating harmonic related issues caused by diode or thyristor rectifier front-ends. To handle the large compensation currents and provide better thermal management, two or more paralleled semiconductor switching devices can be used. In this paper, a novel topology is proposed where two active filter inverters are connected with tapped reactors to share the compensation currents. The proposed active filter topology can also produce seven voltage levels, which significantly reduces the switching current ripple and the size of passive components. Based on the joint redundant state selection strategy, a current balancing algorithm is proposed to keep the reactor magnetizing current to a minimum. It is shown through simulation that the proposed active filter can achieve high overall system performance. The system is also implemented on a real-time digital simulator to further verify its effectiveness.      

基于RLS自适应滤波器的并联型有源电力滤波器

将RLS自适应滤波器用于有源滤波器直流端电容电压的控制，并将直流端电容电压的控制完全摒弃了传统的PI积分控制，解决了控制参数难于调节且对电路中其他参数的变化非常敏感的问题。而且经过自适应滤波器的直流端电容电压几乎没有任何纹波，不但在电源电压为理想情况时可以起到较好的补偿作用，而且当电源电压发生畸变时也有较好的补偿性能。仿真研究证明了所提出的控制方法的正确性。     

并联有源电力滤波器的启动建压与稳压控制

对直流侧电压控制模型,在基于电流正交分解的基础上进行了简化修正,同时考虑检测延迟环节的影响,基于此模型设计了直流侧电压环的PI调节器。文中还设计了一种限流电阻加在线改变电压放大倍数K值的直流侧启动充电方法。最后,采用基于空间电压矢量电流跟踪法的并联型有源滤波器（SAPF）模型进行上述分析的仿真,仿真结果证明该方法可行。     

一种新型高压大功率变频器

针对当前高压大功率变频器在预充电技术上存在的不足,对其进行了改进方案的设计,提出了一种新型高压大功率变频器的设计构想。该新型变频器具有更优的预充电功能,无需高压开关,调试方便,操作性好,有着更好的系统可靠性和安全性,成本低廉,便于广泛应用。     

有源电力滤波器谐波电流的检测方法综述

电网谐波污染日益严重,有源电力滤波器作为谐波抑制的理想解决方案受到广泛的关注。谐波电流的检测性能很大程度上影响有源电力滤波器的补偿效果。根据谐波检测方法依据的理论不同,分为基于功率定义和数字信号处理技术两大类。基于功率定义的谐波检测方法有基于Fryze功率定义、瞬时无功功率理论、同步旋转坐标系、直流侧电压控制等;基于数字信号处理技术的谐波检测方法有基于傅利叶变换、广义积分器、Prony／Kalman估计、小波／S变换、神经网络／自适应滤波。文章详细对谐波检测方法进行归类总结和比较分析,指出了各自的优缺点和适用范围。     

并网有源电力滤波器对谐波抑制的分析

并网逆变器采用有源滤波器能对频率变化的谐波以及变化的无功功率进行补偿,考虑调节的方便与载波频率过低时由调制带来的谐波,研究采用异步调制能达到更好的滤波效果与较强的系统稳定性。     

并联型有源滤波器直流侧电压稳定控制策略

有源滤波器直流侧电压的波动对有源滤波器的稳定运行有很大的影响,针对这个问题,分析了直流侧电压波动产生的原因及对有源滤波器运行的影响,对传统的PI控制提出了基于电压偏差平方的PI控制改进的方法,这种控制直流侧电压的方法对处理传统PI控制的非线性问题也有很大的改进。并通过matlab仿真验证了改进的PI调节控制策略对谐波的消除有很好的效果,这种控制策略通过软件即可实现,不需要增加硬件设备,是一种经济的解决措施。     

并联混合有源电力滤波器的参数设计及仿真

并联混合有源电力滤波器作为一种复杂的电力电子设备,其各个组成部分的参数选取、逆变器的控制策略和系统参数的变化均对滤波性能有一定的影响。文章在分析了这些影响和系统工作原理的基础上,提出一些合适的参数选择方法和控制策略,并用SIMULINK搭建系统模型进行动态仿真验证。     

并联型有源滤波器空间矢量预测电流控制

为了提高有源滤波器(APF)的电流跟踪性能,本文采用电压空间矢量预测电流控制方法。该方法在当前采样时刻预测下一采样时刻的指令电流,计算出APF在下一采样时刻的输出端参考电压,再利用电压空间矢量调制得出控制开关信号,以达到电流跟踪控制目的。仿真实验表明,该方法具有更好的电流控制效果。     

并联型有源滤波器直流侧电压稳定控制策略

有源滤波器直流侧电压的波动对有源滤波器的稳定运行有很大的影响,针对这个问题,分析了直流侧电压波动产生的原因及对有源滤波器运行的影响,对传统的PI控制提出了基于电压偏差平方的PI控制改进的方法．这种控制直流侧电压的方法对处理传统PI控制的非线性问题也有很大的改进。并通过madab仿真验证了改进的PI调节控制策略对谐波的消除有很好的效果,这种控制策略通过软件即可实现,不需要增加硬件设备,是一种经济的解决措施。     

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。