有源电力滤波器空间矢量滞环控制的研究

针对因非线性负载引起的电网谐波污染问题,引入有源电力滤波器(Active power filter,APF)进行治理。分析滞环比较法的工作过程并指出不足,引入空间矢量法解决输出电压相间干扰问题。改进APF的控制策略,把滞环比较和空间矢量结合起来实现电流跟踪控制。最后通过MATLAB/Simulink仿真,比较两种控制策略的仿真结果,证明空间矢量滞环控制具有更好的谐波补偿效果。     

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。     

有源滤波器的研究现状综述

由于现代电力电子技术迅速的快速发展,电力系统中的谐波危害也日益严重,为了有效的抑制谐波提高电能质量,电力有源滤波器APF应运而生,它可以有效的对无功功率和频率、幅值均变化的谐波进行实时跟踪补偿。目前,APF已经成为电力电子技术中的一个重大研究课题。本文介绍了有源滤波器的基本工作原理、谐波电流检测方法及补偿电流控制方法、主电路类型等。     

三相整流桥直流侧和交流侧并联型有源电力滤波器比较研究

三相直流侧和交流侧有源电力滤波器均可用于三相不可控整流桥的谐波治理。从谐波补偿效果、有源滤波器的补偿容量、开关应力三个方面对二者进行了分析和对比。分析结果表明,由于直流侧有源电力滤波器并联在整流桥的直流侧,在换相处的负载电流变化率比交流侧小得多,因此直流侧有源电力滤波器的补偿性能优于交流侧有源电力滤波器。同时由于直流侧有源电力滤波器工作在电压电流两个象限,因此其补偿容量和开关应力远小于交流侧有源电力滤波器。     

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。     

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。     

一种新型恒频滞环电流控制策略研究

并联型有源电力滤波器的变环宽滞环电流控制方法是根据电流幅值的变化适时调整滞环宽度,可有效保证滤波器的补偿性能,控制开关器件的开关频率。在传统的变环宽滞环电流控制算法的基础上,加入了电流限幅和频率PI反馈控制环节,限制了较大电流的波动,提高了频率的控制精度,以及有源电力滤波器的电流补偿性能。Matlab仿真结果表明,采用新型恒频滞环电流控制算法进行电流跟踪补偿时,系统的电流总畸变率小于采用传统变环宽滞环电流控制算法时的总谐波畸变率。     

有源电力滤波器两种检测算法的比较研究

文章研究了有源电力滤波器的两种谐波电流检测算法,ip-iq法对负载电流中的谐波进行全部检测,基于用户侧谐波和无功补偿的检测法仅对用户自身造成的谐波进行检测。仿真结果表明,通过APF补偿后,前者电源电流为正弦波,后者电源电流和电源电压保持相同的畸变率,波形相似。     

有源电力滤波器两种检测算法的比较研究

本文研究了有源电力滤波器的两种谐波电流检测算法,ip—iq法对负载电流中的谐波进行全部检测,基于用户侧谐波和无功补偿的检测法仅对用户自身造成的谐波进行检测。仿真结果表明,通过APF补偿后,前者电源电流为正弦波,后者电源电流和电源电压保持相同的畸变率,波形相似。     

基于PI控制的有源滤波器中的研究

提出了基于并联型三相三线制有源滤波器的优化设计的PI控制方法,该方法的优点是对检测到电流误差信号为控制对象,用滞环比较器构成区域判别器,在此基础上实行滞环电流控制。在同样的控制精度下,该方法可以有效得降低开关频率,减小有源滤波器开关损耗。计算机仿真结果验证了这一方法的有效性。     

Novel compound PWM strategy of a four-leg shunt active power filter

The currently used hysteresis method is of low control accuracy, and the PWM-based strategy fails to provide a high enough response speed; thus, there is always a trade-off between the performances of control accuracy and response speed for a four-leg shunt active power filter (APF) to cope with the large variation in the load harmonic profile. First, an improved SVPWM strategy is proposed in this paper; with the aim to increase the response speed of a four-leg APF by simplifying the implementation of current 3D-SVPWM methods, the principle and realisation of this strategy are explained in detail. Based on these works, a compound PWM algorithm that effectively integrates the improved SVPWM and a PI-based current hysteresis method is proposed to simultaneously guarantee a higher response speed and a higher control accuracy for a four-leg APF. The realisation and parameter tuning of the compound PWM are elaborated. The correctness and effectiveness of the improved SVPWM and the compound PWM strategy are verified by simulations using Matlab/Simulink software. Finally, experimental results on a four-leg APF implemented in a closed-loop real-time simulation platform are presented.     

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.      

基于单片机的有源电力滤波器控制算法的研究

有源电力滤波器的控制是影响其性能的重要因素,它主要是指令电流分离技术及控制算法的应用。为提高APF谐波检测速度和运行精度,通过对指令电流检测技术控制算法的讨论,分析了其对于APF系统性能产生的影响,采用补偿奇次谐波分量的方法,合理选择采样点的位置,提高了AFP系统的性能。     

Unified constant-frequency integration control of active powerfilters-steady-state and dynamics

An active power filter (APF) is a device that is connected in parallel to and cancels the reactive and harmonic currents from a group of nonlinear loads so that the resulting total current drawn from the AC mains is sinusoidal. This paper presents a unified constant-frequency integration (UCI) APF control method based on one-cycle control. This method employs an integrator with reset as its core component to control the pulse width of an AC-DC converter so that its current draw is precisely opposite to the reactive and harmonic current draw of the nonlinear loads. In contrast to previously proposed methods, there is no need to generate a current reference for the control of the converter current, thus no need for a multiplier and no need to sense the AC line voltage, the APF current, or the nonlinear load current. Only one AC current sensor is used to sense the AC main current and one DC voltage sensor is used to sense the DC capacitor voltage. The control method features constant switching frequency operation, minimum reactive and harmonic current generation, and simple analog circuitry. It provides a low cost and high performance solution for power quality control. Steady-state and dynamic study is presented in this paper. Design example is given using a two-level AC-DC boost topology. A prototype was developed to demonstrate the performance of the proposed APF. This control method is generalized to control a family of converters that are suitable for APF applications. All findings are supported by experiments and simulation     

Model Reference Adaptive Control Design for a Shunt Active-Power-Filter System

In this paper, model reference adaptive control (MRAC) is proposed for a single-phase shunt active power filter (APF) to improve line power factor and to reduce line current harmonics. The proposed APF controller forces the supply current to be sinusoidal, with low current harmonics, and to be in phase with the line voltage. The advantages of using MRAC over conventional proportional-integral control are its flexibility, adaptability, and robustness; moreover, MRAC can self-tune the controller gains to assure system stability. Since the APF is a bilinear system, it is hard to design the controller. This paper will solve the stability problem when a linearization method is used to solve the nonlinearity of the system. Moreover, by using Lyapunov's stability theory and Barbalat's lemma, an adaptive law is designed to guarantee an asymptotic output tracking of the system. To verify the proposed APF system, a digital signal controller (dsPIC30F4012) is adopted to implement the algorithm of MRAC, and a 1-kVA laboratory prototype is built to test feasibility. Experimental results are provided to verify the performance of the proposed APF system.     

Neural Network-Based Selective Compensation of Current Quality Problems in Distribution System

Active power filters (APFs) have been used to compensate harmonics, reactive current, and negative sequence fundamental frequency current drawn by nonlinear loads. The control of APF is the core issue for their proper operation. The flexibility of selective compensation embedded in the control scheme makes APF versatile for compensation of reactive power, harmonic currents, and unbalance in source currents and their combinations, depending upon the limited rating of voltage source inverter employed as APF. The proposed scheme utilizes neural network-based decomposition of the load current into positive and negative sequence fundamental frequency component, reactive component and harmonic components. The adaline-based current decomposer estimates the reference currents through tracking of unit vectors together with tuning of the weights. The implementation of the control scheme facilitates selective compensation which respects the limited rating of the APF. The simulated results using developed MATLAB model are presented and are validated by experimental results to depict the effectiveness of the proposed control method of APF     

Temperature‐Dependent Electrical Transport in Polymer‐Sorted Semiconducting Carbon Nanotube Networks

The temperature dependence of the electrical characteristics of field‐effect transistors (FETs) based on polymer‐sorted, large‐diameter semiconducting carbon nanotube networks is investigated. The temperature dependences of both the carrier mobility and the source‐drain current in the range of 78 K to 293 K indicate thermally activated, but non‐Arrhenius, charge transport. The hysteresis in the transfer characteristics of FETs shows a simultaneous reduction with decreasing temperature. The hysteresis appears to stem from screening of charges that are transferred from the carbon nanotubes to traps at the surface of the gate dielectric. The temperature dependence of sheet resistance of the carbon nanotube networks, extracted from FET characteristics at constant carrier concentration, specifies fluctuation‐induced tunneling as the mechanism responsible for charge transport, with an activation energy that is dependent on film thickness. Our study indicates inter‐tube tunneling to be the bottleneck and implicates the role of the polymer coating in influencing charge transport in polymer‐sorted carbon nanotube networks.     

A series active power filter adopting hybrid control approach

The series active power filter (APF) is suitable for compensating a voltage type harmonics-producing load, whereas the control approach it adopts may directly influence its compensation characteristics. This paper first discusses the control approach of detecting source current in terms of the basic operation principle of a series APF, then developing a control approach of detecting load voltage. On the basis of these, a hybrid control approach is proposed. In this approach, the reference signal of the compensation voltage needed by the series APF is obtained by detecting both source current and load voltage. Thus, this approach has the advantages of the first and the second control approaches and, at the same time, it can overcome their respective drawbacks. For practical realization, the control methods of the PWM inverter in the series APF and for regulating its DC side voltage are discussed in detail. A prototype of the series APF is manufactured and corresponding experimental investigation is done. The results show that when the series APF, if adopting the hybrid control approach instead of the other two, compensates for the voltage type harmonics-producing load, its performance can be improved greatly