A shunt active filter for compensating harmonics and unbalance in three-phase four-wire systems

ABSTRACT

This paper introduces a split-capacitor shunt Active Power Filter (SC-APF) based on Synchronous Reference Frame (SRF) theory. This topology is used in compensating the currents of 3-Ph unbalanced non-linear loads. The voltage control loop used in SRF which is only suitable in controlling Four-Leg APF (FL-APF) is modified to control Spilt-Capacitor APF (SC-APF). The proposed scheme provides compensating the 3-Ph unbalanced non-linear loads with lower number of switches, passive elements, and sensors. The performance of the SC-APF with the modified calculation algorithm is verified through simulation and experimental studies.     

基于滑模控制的三相四线制有源滤波器的研究

为了实现三相四线制系统中有源滤波器电流跟踪控制的快速性和鲁棒性．提出了一种基于滑模控制的有源滤波器。在d-q-0坐标系中建立三相四线有源滤波器的数学模型,通过逆系统的方法实现解耦和线性化,并对滑模控制的趋近律进行改进以削弱抖振、加快跟踪速率。仿真结果表明,采用滑模控制实现指令电流跟踪的有源滤波系统鲁棒性强、快速性好、跟踪误差低,总体性能得到明显提升。     

新型三相三线制并联有源滤波器的滑模控制方法

为了提高有源滤波器的谐波补偿效果,设计了一种新型滑模控制器,用于三相三线制并联有源滤波器的参考电流跟踪控制.谐波电流检测方法采用基于瞬时无功功率理论的谐波电流检测方法,能快速、准确的检测出负载电流中的谐波分量.直流侧电压控制方法采用PI控制方法实现.Simulink仿真结果显示,与传统的滞环比较控制方法相比,所设计的新型滑模控制方法能够有效的降低跟踪误差,提高有源滤波器的谐波补偿效果.     

级联型有源电力滤波器的研究

把级联型变流器应用于有源滤波装置是实现大容量谐波补偿的重要途径。介绍级联型有源电力滤波器的基本原理,针对级联型拓扑结构基于瞬时无功功率理论改进了指令电流的计算,使其三相直流侧电压独立控制,满足有源电力滤波器运时对直流侧电压稳定性的要求。用载波相移—正弦脉宽调制(CPS-SPWM)实现电流跟踪控制,并对CPS-SPWM进行了数学分析,同时为了降低启动过程中直流侧电压和电流的过冲,设计一种直流侧预充电方案。最后通过仿真软件MATLAB/Simulink进行仿真验证设计可行性。     

一种新型并联混合型有源滤波器的研究

为实现对非线性负载的谐波补偿和功率因数连续调节,采用了一种无变压器并联混合型有源滤波器,阐述了其工作原理。综合考虑成本与滤波效果的情况下选择采用7次单调谐无源滤波器,针对7次单调谐无源滤波器对于5次谐波补偿能力较差的状况,采用了反馈加5次前馈的控制策略.为了进一步对系统的无功功率进行补偿,在原有的反馈控制环节上进行了一定的改进.仿真结果证明了该并联混合性有源滤波工作的有效性。     

A four-switch shunt active filter based on one cycle control for compensating non-linear loads

ABSTRACT

This paper introduces a Four-Switch Three-Phase Shunt Active Power Filter (FSTP-APF) based on One Cycle Control (OCC) technique for compensating the currents of three phase non-linear loads. The power stage of FSTP-APF uses only four semiconducting switches which leads to reduce the overall cost of APF. The proposed technique retains the advantages of the conventional OCC, such as no reference current calculation, no need for using Phase-Locked Loop (PLL), very simple control circuit and constant switching frequency. In addition, the modification reduces the number of semiconductor switches, reduces the filter output inductances, reducing the number of sensors to only four sensors, two of them for measuring supply currents and the others for measuring DC-link voltages, and the control algorithm becomes simpler. The feasibility and performance of the proposed technique are demonstrated through the simulation and experimental verifications.     

Compensation strategies for shunt active-filter control

Compensation strategies for control of shunt active filters are compared in the paper. It is shown that the strategy based on unity-power factor control is appropriate when the supply voltage waveform of the plant where the active filter is connected shows significant distortion. As voltage distortion increases, this strategy provides compensated line current having lower harmonic distortion and RMS value with respect to the strategy generally used. This contributes to diminish the current and voltage distortion in networks. The unity-power factor compensation strategy conditions the current flowing in the plant where compensation is realized to fit the voltage waveform, thus reaching a unity power factor. Hence, the line current RMS value is minimum. The comparison of the strategies is performed by both Monte Carlo and ATP simulation     

Finite control set predictive control of shunt hybrid power filter

This paper proposes a finite control set predictive control (FCS-PC) scheme for the shunt hybrid power filter (SHPF) to reduce the power loss while maintaining satisfactory power quality at the utility’s grid terminals. By means of the instantaneous power theory, the controller for the proposed method can generate the reference voltage for the SHPF voltage source inverter (VSI) for the future sampling time. Therefore, during a sampling time, the vector of the reference voltage is compared with the finite number of voltage vectors existent in the VSI to select the vector that best fits the cost function of the controller. The proposed method, compared with the conventional pulse width modulation (PWM) carrier method, has the capability of suppressing similarly the harmonic currents at grid terminals and controlling VSI DC-link voltage while maintaining low switching frequencies in the devices. This method shows simplicity in digital implementation because it does not need a PWM block to obtain the VSI gating signals. In addition, a comparison of the proposed FCS-PC method with the conventional carrier-based PWM method is presented and discussed. Parameter errors in the controller are studied and their effects on system performance are explained. The effectiveness of the proposed method is demonstrated with simulation and experimental results during steady-state operation and transient response of the system.     

并联混合型有源电力滤波器的仿真研究

并联混合型有源电力滤波器能很好地补偿谐波源产生的谐波。文中有源滤波器主电路采用3“H桥”共用一个电容的形式。利用MATLAB中的Simulink模块对并联混合型有源电力滤波器进行建模仿真,并对仿真结果进行分析。     

并联有源电力滤波器实用关键技术的研究

随着我国经济和科技的进步,电子装置设备是我国工业化发展必备的配置部分,有源电力滤波器就是其中重要装置.本文主要对并联有源电力滤波器实用关键技术进行研究和分析.     

A passive series, active shunt filter for high power applications

This paper presents a hybrid series passive/shunt active power filter system for high power nonlinear loads. This work is motivated by the fact that the ability of a converter to perform effectively as an active filter is limited by the power and the frequency distribution of the distortion for which it must compensate. This system is comprised of a three-phase shunt active filter and series AC line smoothing reactance installed in front of the target load. The proposed system significantly reduces the required shunt active filter bandwidth. The space-vector pulse width modulation (PWM) controller is based on a dead-beat control model. It is implemented digitally using a single 16-bit microcontroller. This controller requires only the supply current to be monitored, an approach different from conventional methods. The paper provides background on the operation of the filter, the details of the power circuit, the details of the control design, representative waveforms, and spectral performance for a filter which supports a 15 kVA phase controlled rectifier load. Experimental data indicate that the active filter typically consumes 2% or less of the average load power, suggesting that a parallel filter is an efficient compensation approach. The spectral performance shows that the active filter brings the system into compliance with IEEE519-1992 up to the 33rd harmonic for an AC line smoothing reactance of 0.13 p.u     

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.     

A novel shunt hybrid active power filter based on magnetic flux compensation

In this article, the principle of a novel shunt hybrid active power filter (APF) based on magnetic flux compensation is proposed. The parallel transformer can exhibit nearly zero impedance to harmonic current whereas the zero magnetic flux condition is satisfied for harmonics, which leads harmonic current to flow into the transformer branch. Meanwhile, the transformer can exhibit continuously adjustable impedance to the fundamental current based on fundamental magnetic flux compensation, which works together with the passive power filter to compensate for reactive power. A mathematical model is established for system stability analysis and steady state estimation. The experimental results verify that the performance of the proposed APF is satisfactory in harmonic suppression as well as reactive power compensation.     

On the detection of load active currents for active filter control

The control of current source converters used as active filters can be based on either the current active components detection or the instantaneous imaginary power detection from which all or only a part can be used. The authors study the conditions in which this second method is equivalent to the first one and propose an improvement for the cases when it is not so     

基于单片机控制的程控有源滤波器电路

集成开关电容有源滤波器具有良好的幅频特性,改变其开关频率,就可方便地改变滤波器的工作频率。利用单片机灵活控制特点,实现对集成开关电容滤波器的工作频率、品质因数Q和工作方式的程控。     

DSP-based active power filter with predictive current control

This paper presents an active power filter based on a digital signal processing (DSP) controller with enhanced current control performance. A novel predictive current control method is introduced to compensate the phase error of harmonic components caused by discrete sampling and finite nonnegligible execution time delay. The concept of average current control is also introduced that is adequate for digital current control. With a close coordination between the reference current prediction, PWM pattern generation, and control timing, a high performance control is achieved. Experimental results show that the developed system gives satisfactory performance in harmonic and reactive power compensation     

Inductance optimisation method of a four-wire shunt APF based on unified mathematical model

Leg inductors which connect a shunt Active Power Filter (APF) to power network play a crucial role in guaranteeing desired performances of the APF. Optimal tuning of the inductances is still a tricky problem that has not yet been tackled systematically and theoretically. This paper proposes a novel inductance optimisation method that is universally applicable to four-wire shunt APFs with arbitrary topologies and PWM strategies. Based on the unified mathematic model, indexes used to quantitatively evaluate the abilities of a four-wire APF in compensating phase harmonic currents and depressing neutral line current are formally formulated. The upper and lower value constraints of the inductances are derived by comprehensively taking into account the characteristics of load harmonic profile and PWM strategy. Inductances are further optimised in the feasible value ranges with concern of several engineering application issues. Simulation and lab experiment results are provided to verify the validity and effectiveness of the proposed method.     

An improved control algorithm of shunt active filter for voltageregulation, harmonic elimination, power-factor correction, and balancingof nonlinear loads

This paper deals with an implementation of a new control algorithm for a three-phase shunt active filter to regulate load terminal voltage, eliminate harmonics, correct supply power-factor, and balance the nonlinear unbalanced loads. A three-phase insulated gate bipolar transistor (IGBT) based current controlled voltage source inverter (CC-VSI) with a DC bus capacitor is used as an active filter (AF). The control algorithm of the AF uses two closed loop PI controllers. The DC bus voltage of the AF and three-phase supply voltages are used as feedback signals in the PI controllers. The control algorithm of the AF provides three-phase reference supply currents. A carrier wave pulse width modulation (PWM) current controller is employed over the reference and sensed supply currents to generate gating pulses of IGBTs of the AF. Test results are presented and discussed to demonstrate the voltage regulation, harmonic elimination, power-factor correction and load balancing capabilities of the AF system     

Digital signal processing strategies for active noise control

Over the last few years the increase in processing power available from digital signal processors has allowed active noise control to become a viable real-world technology. This paper reports on the development of a two channel active noise controller using low-cost DSP technology and presents illustrative results for a variety of real-world applications     

Analysis and control of active power filter with optimizedinjection

An active filter that removes harmonics from the AC line by the injection of pulse-width-modulated (PWM) controlled currents is described. These compensating currents are optimized for the removal of all harmonic components up to a specified order using a filter that requires no supply other than the line to which it is connected. The required bidirectional power flow in the filter is achieved by establishing an internal inductor current within upper and lower limits by a purely fundamental current flow into the filter from the line. The performance characteristics of the proposed method are investigated by analysis and simulation. Experimental results from a microcomputer-controlled model establish the validity of the approach