Active power filter based on three-phase two-leg switch-clamped inverter

A novel three-phase two-leg switch-clamped inverter is presented to achieve multilevel pulse-width modulation (PWM) operation, harmonics elimination, reactive power compensation and dc-link voltage regulation. Four active switches with voltage stress of dc-link and two ac switches with voltage stress of half dc-link are used in the proposed inverter. In this paper, the proposed inverter is operated as a controllable current source to supply the necessary active power for the compensation of inverter losses, to suppress current harmonics, and to compensate the reactive power drawn from the non-linear loads. Therefore, the balanced and sinusoidal line currents are drawn from the ac source. Two control loops are used in the adopted control scheme to maintain the constant dc-link voltage (outer loop with low-bandwidth control) and to achieve the line current command tracking (inner 1oop with high-bandwidth control). The mathematical model of the proposed converter for the operation active power filter is derived and the control scheme is provided. Computer simulations and experimental results based on a laboratory scale-down prototype are presented to verify the effectiveness of the proposed control scheme.     

配电系统级联多电平有源电力滤波器仿真研究

笔者研究了将级联多电平拓扑应用于有源电力滤波器(APF)的方法.在调制方法上采用载波移相的调制技术,在控制上采用简单的PI控制方法.仿真结果表明,这种基于级联多电平拓扑的有源电力滤波器能很好地跟踪补偿电网谐波,具有很好的动态响应和较高的检测精度,并且快速准确地实现各个变流器单元直流侧电容的均压控制,这对拓展有源电力滤波...     

适用于二极管钳位型三电平有源滤波器的母线电压数字控制方法

传统两电平有源电力滤波器(active power filter, APF)由干功率开关耐压水平和载流能力的限制,难以实现对高压大容量非线性负载的谐波补偿。在高压大容量系统中,二极管钳位型三电平变换器得到了广泛的应用。对三电平APF进行研究,提出一种母线电压闭环数字控制策略。在同步旋转dq坐标系下,将三电平APF母线电压控制系统分为电压外环和电流内环2部分。在电压外环中,采用自适应滤波器求出直流侧电压平均值,采用PI控制器产生有功指令电流维持直流侧电压恒定。在电流内环中,针对三电平APF直流侧中点电位不平衡问题,从空间矢量PWM调制方法的角度出发,对中点平衡问题进行仔细研究,提出一种简单的中点电压平衡控制策略,只需检测各相电流和中点电压波动的方向,对小矢量进行取舍实现APF中点电位平衡控制。实验结果表明了所提出算法的正确性和有效性。     

Application of type-2 fuzzy logic controller to an induction motor drive with seven-level diode-clamped inverter and controlled infeed

This paper describes a new control method for the integrated of six current rectifiers—seven-level diode-clamped inverter feeding induction motor considering dc-link capacitors voltage balancing problem. The proposed controller uses type-2 fuzzy systems to compensate the fluctuations of capacitors voltage, draw a sinusoidal line current with nearly unity power factor, and ensure the motor speed control. The performance of dc-link voltages control is evaluated in comparison to the conventional PI control scheme. The overall system and the control algorithm are presented and a set of simulations is carried out in order to prove the good performances of the proposed solution.     

Robust predictive dual-loop control method based on Lyapunov function stability and energy equilibrium though double-core processors for active power filter

In this paper, a robust predictive dual-loop control method based on Lyapunov function stability and energy equilibrium for active power filter (APF) is proposed to improve the anti-interference performance and self-adaptive capability of system. The proposed control method mainly includes robust predictive current control based on Lyapunov function stability (RPCC-LFS) in the inner current loop and energy equilibrium proportional-integrator (PI) control in the outer dc-link voltage loop. The RPCC-LFS is proposed to enhance self-adaptive capability when the output filter inductors vary, speed up the dynamic response, and improve the tracking accuracy when the loads fluctuate. The energy equilibrium PI controller is proposed to maintain the dc-link voltage stable and suppress the transient impulse. The stability and dynamic response of the proposed control system are analyzed in detail, and the proper control parameters are selected. A specific hardware and software design program based on double-core processors DSP + FPGA is thoroughly given out. Finally, the comparative simulations and experiments verified the validity of the proposed method.     

Robust Model-Following control of a three-level Neutral Point Clamped shunt active filter in the medium voltage range

This paper presents a robust control technique applied to a three-phase shunt active filter based on an NPC inverter, showing the modelling procedure needed to carry out the proposed control. The transfer functions for the control of the currents injected by the active filter are derived. The modelling is based on the abc/dq Park transformation of the AC system variables. The currents injected by the active filter are controlled in the synchronous orthogonal dq reference frame. The proposed robust current control technique is compared to a conventional PI controller in the dq frame, and to a PIS controller in the dq frame, consisting of a PI and resonant controllers synchronized to the frequencies of the nonlinear load current harmonics. On one hand, it is shown that the proposed technique improves the current harmonics compensation obtained by conventional PI control. On the other hand, it is found that the PIS controller is the best suited for current harmonics compensation among the controllers under study. Nevertheless, the RMF controller results in a simpler implementation than the PIS controller. Moreover, the proposed robust control has been applied to the DC-link voltage regulation, and it has been compared to a PI controller. It is shown that the robust control technique improves the dynamic response of the inverter to load steps without the need of a high crossover frequency of the DC-link voltage loop.     

基于级联多电平的有源滤波器直流侧电压平衡控制

为了减小电网中非线性负载带来的谐波电流对电网质量的影响,针对基于H桥的有源滤波器装置中直流电容电压问题,提出一种新的控制方法。将控制模块分成模块均值电压控制器和直流母线电压控制器两个部分,通过调节每个H桥之间的有功功率交换和有源滤波器同电网间有功功率的交换来实现直流电容电压的平衡控制。利用该方法对八个单元H桥级联的并联型有源滤波装置进行Matlab/Simulink仿真,并基于FPGA+DSP实验平台搭建了三单元H桥级联样机。仿真和实验结果表明,基于级联多电平的有源滤波器直流侧电压平衡控制方法是有效和实用的。     

三电平有源滤波器直流侧电压控制方法

建立了三电平有源滤波器数学模型并提出了其直流侧电压的闭环控制策略。在电压外环中采用PI控制维持直流侧电压恒定。在电流内环中,从空间矢量PWM调制方法的角度出发,对中点平衡问题进行了仔细研究,总结了各种空间矢量对中点电压平衡的影响。然后针对三电平APF,提出了一种简单的中点电压平衡控制策略。该方法只需检测各相电流和中点电压波动的方向,对小矢量进行取舍实现中点电压平衡控制。同时,并没有增加系统的开关损耗和输出电压的du/dt。仿真结果证明了这种控制策略的正确性。     

级联型中压有源电力滤波器的研究与实现

中压和低压配电网的有源电力滤波器(APF)在检测方法和控制方法理论上是一致的。然而,受电力电子主电路电压和电流容量的限制,中压配电网的APF尚处于研究阶段。目前广泛研究的中压APF主电路结构形式主要有有源无源混合结构和多电平级联结构两种。在分析以上两种结构的特点基础上,采用一种带隔离变压器的级联型多电平逆变器作为APF主电路,具有结构简单,直流电压容易控制等显著特点。并将多载波调制和滞环电流矢量控制方法应用于实际实验装置,实验结果证明了结构和控制方法的可行性。     

Control of a 3-phase 4-leg active power filter under non-ideal mains voltage condition

In this paper, instantaneous reactive power theory (IRP), also known as p–q theory based a new control algorithm is proposed for 3-phase 4-wire and 4-leg shunt active power filter (APF) to suppress harmonic currents, compensate reactive power and neutral line current and balance the load currents under unbalanced non-linear load and non-ideal mains voltage conditions. The APF is composed from 4-leg voltage source inverter (VSI) with a common DC-link capacitor and hysteresis–band PWM current controller. In order to show validity of the proposed control algorithm, compared conventional p–q and p–q–r theory, four different cases such as ideal and unbalanced and balanced-distorted and unbalanced-distorted mains voltage conditions are considered and then simulated. All simulations are performed by using Matlab-Simulink Power System Blockset. The performance of the 4-leg APF with the proposed control algorithm is found considerably effective and adequate to compensate harmonics, reactive power and neutral current and balance load currents under all non-ideal mains voltage scenarios.     

一种高性能单相电网有源滤波器的设计

设计了一种高性能的单相电网有源滤波器。该有源滤波器主功率回路采用电压源型H桥逆变器,逆变器开关驱动信号为特定消谐PWM开关信号。控制回路采用PI电压跟踪控制,不需实时检测计算负载的无功电流和高次谐波电流,就可以实现同时补偿负载无功及高次谐波电流的需求。分析了滤波器的补偿特性和各主要单元电路的设计方法,实验结果证明该有源滤波器的有效性。     

Implementation of active power filter with asymmetrical inverter legs for harmonic and reactive power compensation

An asymmetrical voltage source inverter is proposed to operate as an active power filter to eliminate harmonics and compensate reactive power drawn from the nonlinear loads such that a sinusoidal line current is drawn from the ac source. Two inverter legs are used in the adopted circuit configuration. One inverter leg is operated in the line frequency and the other leg is operated in the high switching frequency to track the compensated current command. In the proposed control scheme, a voltage compensator, a carrier-based current controller and a proportional integral-based dc link controller are used to achieve balanced capacitor voltages, to track line current and to obtain a constant dc bus voltage, respectively. Based on the pulse-width modulation (PWM) control scheme, a three-level voltage pattern is generated on the ac terminal of the inverter. Computer simulation and experimental results are provided to verify the effectiveness of the control scheme.     

基于高频隔离的负序级联式补偿电路拓扑

提出了一种可以级联应用于高压场合的负序电流补偿电路拓扑。此电路通过内部相互耦合的高频隔离变压器进行负序能量交换,实现了对于三相四线制或者三相三线制中不平衡电流的补偿。这种拓扑克服了传统按照星型连接的电压型H桥级联构成的APF应用于高压系统中无法进行负序电流补偿的缺点,实现了相间能量交换,并且能够在单级和多级级联后均可进行无功,谐波和负序电流的补偿。系统通过三绕组变压器降低了直流侧电容电压的二次脉动,减小了所需电容量。文章通过对两级级联系统的仿真,证实了电路拓扑的可行性,所构建的小功率实验平台进一步验证了所提出方案的有效性。     

Sinusoidal Pulse-width Modulated Three-phase Multi-level Inverter Topology

Abstract—This article presents a sinusoidal pulse-width modulated three-phase multi-level inverter topology. In this configuration, the basic two-level, three-phase inverter is modified to synthesize higher voltage levels by the insertion of two auxiliary switches per phase leg. The multi-level inverter configuration generates output voltage levels similar to the corresponding well-known conventional diode-clamped flying capacitors and cascaded H-bridge inverters but with fewer power circuit components and more simplicity. For output voltage and frequency variations demanded by such applications as variable-speed drives, active power filters, photovoltaic power conversions, etc., the sinusoidal pulse-width modulation technique is employed in the generation of the gating signals for the proposed three-phase multi-level inverter. A balanced three-phase R-L load is applied at the inverter output terminals, and the inverter performance is compared with that of other sinusoidal pulse-width modulated conventional multi-level inverter configurations. The validity of the proposed multi-level inverter topology and the modulation scheme are verified through simulations and experiments.     

Cascaded Common Nodal Point Multi-level Inverter Topology

Recent trends in the multi-level inverter (MLI) technology demand reduced number of switches, driver circuits, isolated DC sources, peak inverse voltage (PIV), appreciable number of voltage level, and lower total harmonic distortion. This paper presents an improved cascaded MLI configuration. Each module comprises ten switches, two isolated DC sources, and two capacitors; it can generate a maximum of 9-level output voltage waveform. Optimized switching sequence is developed that ensures minimum switching transitions and is implemented through single-carrier pulse width modulation for the control of the proposed topology. The classical cascaded H-bridge inverter and some recently developed MLI configurations were compared with the proposed inverter circuit. Results show that the proposed inverter configuration generates high number of output voltage levels with reduced number of power switches and PIV. It also has a lower per-unit power loss profile. Unit capacitor voltage balancing scheme is developed, which ensures proper control of the unit step voltage level in each of the cascaded modules, at extreme loading condition. For two cascaded inverter modules, simulation and experimental verifications are carried out on the proposed inverter for an R–L load. Simulation results of the output voltage waveforms and its harmonic spectrum are in conformity with experimental results.     

Analysis and effective controller design for the cascaded H‐bridge multilevel APF with adaptive signal processing algorithms

The cascaded H‐bridge (CHB) multilevel inverter is being recognized as the most suitable topology for high‐power medium‐voltage power quality conditioning applications. This paper presents mathematical modeling and effective controller design methodology for the CHB‐based active power filters (APFs), which achieves dynamic reactive power and harmonic compensation. The most crucial problems in CHB‐APF control are the simultaneous requirements of both accurate harmonic current compensation and the dc‐link voltage stabilization among the H‐bridges, which is the prerequisite for the stable operation of CHB‐APF. To achieve dc‐link stabilization, a novel voltage balancing algorithm is proposed by splitting the dc‐link voltage 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 component of the grid voltage are used, respectively. To ensure accurate phase tracking, a novel phase‐locked loop (PLL) is proposed by using the adaptive linear neural network (ADALINE), where the grid voltage background distortion is also taken into account. The superior performance of the ADALINE‐PLL is validated by comparison with the existing PLLs in literatures. Furthermore, the proportional‐resonant (PR) controller is used for the reference current tracking. A separate ADALINE algorithm is applied for reference current generation (RCG) for the CHB‐APF. The excellent performance of the ADALINE‐based RCG scheme is verified by comparison with the existing RCG schemes, namely, the low‐pass filter approach and the single‐phase p ? qmethod. The experimental results on the three modules CHB‐APF are presented, which verifies the effectiveness of the proposed control algorithms. Copyright © 2011 John Wiley & Sons, Ltd.     

并联型有源电力滤波器的重复学习Boost变换控制策略

将供电系统谐波电流的补偿应用戴维南定理等效为谐波电压源的补偿,由此提出了一种基于Boost变换技术的PWM逆变器重复学习控制策略.该控制策略一方面将逆变器视为PWM整流器,应用Boost控制方法,使系统谐波电流与等效谐波电压源形成近似单位功率因数;另一方面,采用内部模型控制将系统谐波电流直接转换形成常规PWM逆变器的控制电压,并且应用重复学习控制消除各种不确定性因素对控制品质的影响.仿真和实验结果证实该控制器适合于有源滤波器系统,并具有跟踪速度快,鲁棒性好、稳态误差小等特点.     

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。     

负载不对称H桥级联APF直流电压平衡控制

H桥级联型有源电力滤波器(APF)在高压场合的谐波处理方面具有广阔的应用前景。三相三线制系统下负载不对称时,APF输出的基波电压和电流产生不同的有功分量分配至三相,再加上H桥各个模块的差异等原因,导致直流侧电压不均衡,影响APF的正常运行。通过对级联APF功率模型的推导,控制APF输出基波正序有功电流稳定全局电压、输出基波负序电流实现三相之间电压均衡。在全局稳压和相间均压条件下,控制各H桥交流侧输出补偿有功电压矢量实现相内电压均衡,最终将每个H桥直流电压维持在给定值附近,同时APF补偿谐波电流,降低网侧电流THD。在低压条件下的仿真和实验结果验证了所用方法的可行性,为级联APF向更高电压等级场合的应用提供了基础。     

SHPF-TCR联合控制补偿系统的研究

针对有源电力滤波器无法动态补偿无功功率,无源滤波器补偿产生相移的问题,提出一种晶闸管控制电抗器与并联混合电力滤波器(SHPF-TCR)联合补偿控制系统。SHPF由小容量有源电力滤波器和五次LC单调谐滤波器构成以补偿系统谐波,调谐滤波器和TCR形成并联型无源滤波器以补偿系统无功。将解耦控制用于电流跟踪和电压调节,引入PI控制器消除系统稳态误差。该SHPF-TCR联合控制能够有效的降低APF容量,消除系统谐振,稳定性好,动态响应速度快。实验及仿真结果证明了所提出结构和控制方法可以很好地进行谐波和无功的综合补偿。