Hybrid solutions for improving passive filter performance in highpower applications

This paper presents a new control scheme for a parallel hybrid active filter system intended for harmonic compensation of large nonlinear loads up to 50 MVA, to meet IEEE 519 recommended harmonic standards. The active filter is small rated, 2%-3% of load kilovoltampere rating. The control scheme is based on the concept of synthesizing a dynamically variable inductance, and its usefulness is demonstrated for an active filtering application. A synchronous reference frame (SRF) controller implements the dynamically varying negative or positive inductance by generating active filter inverter voltage commands. This variable inductance controller parallel hybrid active filter system can selectively synthesize multiple “active inductances” at dominant harmonic frequencies without affecting passive filter impedances at all other frequencies. This controller also provides a “current limiting” function to prevent passive filter overloading under ambient harmonic loads and/or supply voltage distortions. Three implementation variations of a parallel hybrid active filter system are presented. This paper also proposes the use of power factor correction capacitors as low cost passive filters for a parallel hybrid active filter system, which are controlled to provide either single or multiple tuned harmonic sinks and to increase cost effectiveness for high power applications. Simulation results validate the proposed variable inductance controller operation for mistuned passive filters     

A closed-loop selective harmonic compensation for active filters

This paper proposes a control algorithm for parallel active power filters, based on current-controlled pulsewidth-modulated converters, which allows precise compensation of selected harmonic currents produced by distorting loads. The approach is based on the measurement of line currents and performs the compensation of the selected harmonics using closed-loop synchronous frame controllers. Thanks to the closed-loop operation, full compensation of the desired harmonics is achieved even in the presence of a significant delay in the current control. Thanks to the selective approach, active filter interactions with possible dynamic components of the load are minimized. Moreover, the complexity of the synchronous frame controllers is overcome using equivalent stationary frame controllers. Experimental results confirm the theoretical expectations     

Stationary frame harmonic reference generation for active filter systems

Harmonic reference generators for active filter systems are commonly implemented in the synchronous reference frame, so that simple low- or high-pass filter functions can be used depending on the requirements of a particular application. High-pass filters in particular are used when the reference generator is required to produce an "everything but the fundamental" target waveform. This paper presents a stationary frame notch filter equivalent to a high-pass synchronous frame harmonic reference generator for such systems. The use of the stationary frame allows for quicker calculation of the reference generation in a discrete digital implementation, and also allows classical control techniques to be used to analyze the active filter system without requiring synchronous frame transformations of the outside system model. Both simulation (continuous and discrete) and experimental results showing the equivalency of the stationary and synchronous frame reference generation process are presented using both shift and delta-operator-based infinite-impulse response digital filters.     

三相并联型有源电力滤波器补偿电流性能分析与改进

三相有源电力滤波器通常用来补偿非线性负载所引起的谐波和无功电流。在有源电力滤波装置中，其补偿性能的好坏，很大程度上取决于控制器的设计。但由于非理想因素的影响，例如输出电流环路带宽有限、检测电路的延时、指令电流的产生等，都会影响补偿效果，而传统的PI控制由于带宽有限不能实现无静差输出。为了提高三相并联型有源电力滤波器的补偿性能，该文在同步旋转坐标系下提出了一种理想的电流控制策略即基于PI控制和重复控制并联结构的电流控制方法，利用重复控制对于周期扰动信号无差跟踪的特点来提高有源滤波的稳态精度，PI控制保证有源电力滤波器的动态性能。实验结果和理论分析充分证明了所提并联结构电流控制器的可行性。     

Direct power control of a multilevel inverter based active power filter

A cascaded H-bridge multilevel inverter based active power filter with a novel direct power control is proposed in this paper. It can be directly connected to medium/high voltage power line without using the bulky transformer or passive filter. Due to the limited switching frequency (typically below 1 kHz) of high-power solid-state devices (GTO/IGCT), multiple synchronous/stationary reference frame current controllers are reviewed and derived. Based on this, a novel current controller is proposed for harmonic current elimination and system power factor compensation. Furthermore, a synchronous/stationary hybrid structure can be derived with fundamental de-coupling control. The instantaneous reactive power theory and synchronous reference frame based control are compared based on mathematical models. A direct power control concept is then derived and proposed. It is equivalent as the hybrid synchronous/stationary frame current controller, but has a simpler implementation. It has clear physical meaning and can be considered as a simplified version of the hybrid frame current controller. Simulations on a 4160 V/1.2 MVA system and experimental results on a 208 V/6 kVA laboratory prototype are presented to validate the proposed active power filter design.     

并联型直流有源电力滤波器的控制系统设计

并联型直流有源电力滤波器可以有效抑制高压直流输电线路谐波,但该滤波器对其控制系统的性能要求也较高。文中采用输电电流高增益反馈控制方法作为控制策略,并依此方法确定了各项设计参数。同时,针对该控制方法的要求基于数字信号处理器(DSP)和现场可编程门阵列(FPGA)设计了一套控制器装置。该装置通过锁相环实现了同步采样和控制。该方法既提高了谐波检测准确度,又能使数字滤波处理的通带频率自动跟踪系统频率变化。该装置实现了一种具有较小相移的脉宽调制模块,保证了谐波抑制性能和滤波系统的稳定。基于该控制系统的样机实验获得了良好的谐波抑制效果。     

LCL滤波的双馈式风电网侧变流器在不平衡电网电压条件下的控制策略

为了提高LCL滤波的双馈式风电网侧变流器在电网电压不平衡情况下的工作性能,通过对变流器在上述条件下的数学模型进行理论分析,提出了基于LCL滤波器的不平衡电流指令算法,并提出了在同步旋转dq坐标系下采用PI和重复控制器并联结构的电流复合控制方案.利用所提控制策略,可有效降低电网电流中的低次谐波含量,实现正负序电流的无差跟...     

基于PI+QPR控制的单相有源电力滤波器研究

单相系统中,利用并联型有源电力滤波器(Active Power Filter,APF)进行谐波治理时,传统的电流比例积分(Proportional Integral,PI)控制方式具有较快的响应速度,但3次谐波电流不能得到充分抑制,针对这一问题采用准比例谐振控制器对3次谐波电流进行跟踪控制。APF系统采用LCL型滤波器结构与单相系统相连,使用陷波滤波器对ip-iq谐波电流检测算法进行改进,以提高谐波电流检测精度,消除数字低通滤波器输出侧直流信号中的低频波动问题。最后通过Matlab/Simulink建立单相并联型APF谐波治理系统模型,验证了所提控制策略的可行性和有效性。     

Harmonic current and voltage compensation using HSAPF based on hybrid control approach for synchronous reference frame method

This paper presents a Hybrid Series Active Power Filter (HSAPF) for compensation of source current and load voltage harmonics. The HSAPF combination consists of a small rated series active power filter and a shunt connected passive power filter. This combination is suitable for compensation of voltage-type as well as current-type harmonic producing load. The HSAPF uses the synchronous rotating reference frame method that based on hybrid control approach, which eliminate both source current as well as load voltage harmonics and also tests the performance of HSAPF for ideal voltage, non-ideal voltage and also at different loading conditions, etc.     

基于磁通补偿的新型有源电力滤波器的暂态特性分析

笔者提出一种新型单相并联混合型电力滤波方案。该方案采用磁通补偿原理和谐波电流分流技术,可以进一步降低APF所需容量,并有效改善滤波系统的性能。为分析该方案的相关特性,文中建立了它的稳态及暂态过程数学模型。重点分析PID控制器比例、积分、微分参数kp、ki、kd对暂态过程中的滤波特性和APF所需容量的影响,分析结果表明,控制器参数设置对滤波器暂态特性有重要影响,该分析为PID参数的设计提供了一定的理论参考。     

新型谐振式混合有源滤波器的研究

为减小有源滤波器的容量,提出了一种新型混合有源滤波器的拓扑结构。其基本思想是:根据分流原理,适当控制有源部分来等效增大系统支路的谐波阻抗,提高无源滤波器的滤波效果;将有源部分与基波谐振电路并联来减小有源部分容量;合理地配置注入支路的参数,以保证滤波器具有较好的滤波能力和一定的无功补偿能力。仿真和实验结果证明了所提出的混合有源滤波器的可行性和正确性,所提出的拓扑结构消耗的有效材料少,体积小,占地面积小。     

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.     

A novel lowpass to bandpass transformed PI control strategy for series hybrid active power filter

In this paper, simulation and experimental based evaluation of novel lowpass to bandpass transformed PI control strategy for series hybrid active power filter is presented. In the series hybrid topology, the active filter is in series with a capacitor and this whole arrangement comes in parallel with an inductor. This hybrid setup is introduced in series between the source and load. The control structure is derived in the stationary reference frame through lowpass to bandpass transformation of ordinary PI controller transfer function. The effect of controller on system performance as well as its selective harmonic elimination is illustrated. The modelling, simulation and experimental results are presented.     

多相构造法在单相有源电力滤波器谐波电流检测中的应用

瞬时无功理论在三相有源电力滤波系统的谐波及无功电流检测中获得了广泛的应用。提出了使用移相构造法将瞬时无功理论应用于单相有源电力滤波系统谐波电流的检测。同时还介绍了将负载电流移相任意角度后构成两相电流在旋转坐标下进行电流谐波检测的方法。分别给出了其理论分析过程及应用在单相并联有源电力滤波系统中的仿真结果，通过仿真结果验证了结论。     

移相构造法在单相有源电力滤波器谐波电流检测中的应用

瞬时无功理论在三相有源电力滤波系统的谐波及无功电流检测中获得了广泛的应用。提出了使用移相构造法将瞬时无功理论应用于单相有源电力滤波系统谐波电流的检测。同时还介绍了将负载电流移相任意角度后构成两相电流在旋转坐标下进行电流谐波检测的方法。分别给出了其理论分析过程及应用在单相并联有源电力滤波系统中的仿真结果,通过仿真结果验证了结论。     

基于DFT谐波检测方法的大容量并联型有源电力滤波器的研制

本文介绍了采用多重化主电路设计、基于离散傅立叶变换(DFT)谐波检测方法的100kVA并联型有源电力滤波器的研制情况.文章对并联型有源电力滤波器补偿谐波与无功电流的工作原理进行了分析,论述了选择DFT作为电流检测算法的优点,并对采用二重化方法设计的主电路结构以及相应控制策略的实现方法进行了介绍,最后给出了实验结果.实验证明,该系统满足设计要求,补偿效果良好.     

基于空间矢量的有源电力滤波器预测电压控制策略

从矢量的角度出发,将三相电网电压与电流矢量在旋转坐标系下进行投影变换,实现了谐波与无功电流的同时提取。进一步提出一种具有无差拍控制特性的有源电力滤波器空间矢量控制策略,实现了有源电力滤波器的预测控制和谐波与无功电流的精确补偿。利用MATLAB对所提出的控制策略进行仿真验证,并研制了5 kVA实验样机进行了实验研究。仿真与实验结果验证了此方法的正确性与有效性。     

An active filter for an unbalanced three-phase system using the synchronous detection method

This paper presents an active filter using the synchronous detection method. The equal-current synchronous detection method (CSD) is applied to calculate the reactive and harmonic current compensation components for triggering an active filter in an unbalanced three-phase power system. The experimental results of active filter operation using the synchronous detection method show that it is effective in eliminating line current harmonics and compensating the reactive current component. The merits of the proposed method are its capability to operate under an unbalanced three-phase system by per-phase calculation, to avoid conversion error by forced waveform calculation, to balance the unbalanced load and to accomplish a good performance with a very simple implementation.     

人工神经网络在电能质量调节器中的应用仿真研究

运用人工神经网络控制模式和一种新型控制算法,设计了一种可同时补偿无功和抑制谐波的并联有源电力滤波器.经MATLAB仿真,结果证明,所提出的有源电力滤波器控制技术及其控制算法,对消除谐波和补偿无功电流起到了更好的作用.     

移动平均在并联有源电力滤波器中的应用

在并联型有源电力滤波器的设计中,若采用d,q同步旋转变换来提取谐波电流,则低通滤波器(Low Pass Filter,简称LPF)是设计的关键环节.介绍了d,q同步旋转变换和采用移动平均算法的LPF的基本原理,并通过仿真与常用的Butterworth LPF相比较,证明了移动平均算法在动态响应速度(15 ms以内)和稳态精度方面具有一定的优势.经试验验证,动态响应速度为15 ms,补偿后电流的THD达到2%左右,由此得出结论,基于移动平均算法的LPF具有优良的动态响应速度和稳态精度.