An Efficient Particle Swarm Optimization Technique for 4-Leg Shunt Active Power Filter

This paper describes the mitigation of harmonics in source and neutral current in three phase four wire system based on 4-leg shunt active power filter under balanced and unbalanced load conditions. Particle Swarm Optimization (PSO) and conventional Proportional Integral (PI) controller are used as control techniques to analyze the control performance of 4-leg shunt active power filter. The synchronous reference frame (SRF) method is used to extract reference current in 4-leg shunt active filter. The Hysteresis Current Controller (HCC) is used to generate gate pulses for Voltage Source Inverter (VSI) based 4-leg shunt active power filter. The proposed PSO technique gives less percentage of Total Harmonic Distortion (THD) value in source and neutral current and settling time of the DC capacitor voltage compared to conventional PI controller technique. The model of the proposed system performance was validated using MATLAB/Simulink environment.

Current control for a shunt hybrid active power filter using recursive integral PI

This paper presents a current control method for a shunt hybrid active power filter （HAPF） using recursive integral PI algorithm. The method improves the performance of the HAPF system by reducing the influence of detection accuracy, time delay of instruction current calculation and phase displacement of output filter. Fuzzy logic based set-point weighing algorithm is combined in the control scheme to enhance its robustness and anti-interference ability. The proposed algorithm is easy to implement for engineering applications and easy to compute. Experiment results have verified the validity of the proposed controller. Furthermore, the proposed recursive integral PI algorithm can also be applied in the control of periodic current as in AC drivers.

A Novel Starting Impulse Suppression Method for Active Power Filter Based on Slowly Rising Curve

With the widespread application of power electronic equipment in the power grid,the harmonic problem of the power grid becomes more pronounced,reducing the efficiency of power production,transmission,and utilization,and interfering with the normal operation of the power grid.Based on the requirements of harmonic suppression and power system protection,a shunt active power filter(SAPF)is proposed as an effective harmonic suppression method.However,there are problems with impulse current and impulse voltage in the starting process of SAPF.Impulse current and impulse voltage cause the power grid and switchgear to bear greater current stress and voltage stress,which seriously affect the security and reliability of the power grid and may damage the switchgear.To effectively solve the problem of impulse current and impulse voltage,the starting process of SAPF is divided into the uncontrolled rectification stage and the transition stage.The mathematical model of the DC side of APF is established.The causes of impulse current and impulse voltage in the uncontrolled rectifier and transition phases are analyzed.By introducing voltage square,a new starting impulse suppression strategy of active power filter based on the slow rising curve is proposed,fundamentally solving the problems of impulse current and impulse voltage.Simulation results verify the effectiveness and feasibility of this method.

Power Quality Comparative Analysis between UPF and SAPF

This paper makes a technical analysis of the converter’s topologies that are conventionally employed in three-phase three-wire in increasing the power factor and harmonics eliminating,namely unit power factor(UPF)and shunt active power filter(SAPF)and highlights the improvement of energy quality in the supply network.The paper highlights that the mathematical model of the three-phase PWM rectifier in the dq coordinate system is similar for both configurations.The structure of the control schemes of the two topologies for increasing the energy quality is similar by transformation of three-phase stationary coordinate system(a,b,c),to synchronous rotating(d,q)coordinate system that synchronously rotates with the fundamental voltage of the grid.Theoretical analysis and simulation results show that the control in synchronous rotating coordinate system has high power factor and low THDi for the both topologies.

Increasing the operating area of shunt active filters by advanced nonlinear control

This work is aimed to rigorously manage voltage saturation and maximum current constraints in Shunt Active Filters. In this respect, assuming 'unconstrained' control algorithms have already been defined to achieve standard objectives for such devices(i.e. current tracking for harmonic compensation and DC-bus voltage boundness), a plug-in unit, oriented to extend the system operating region and at the same time preserving good performance under large transients and overload conditions, is presented.This solution allows to improve availability, robustness and composability of Shunt Active Filters, which are expected to be key features in present and next generation complex and possibly 'smart' power grids. The proposed unit is composed by two parts.First, a suitable anti-windup strategy is defined in order to deal with control input saturation. Its main purpose is to preserve the original 'unconstrained error dynamics', in face of input saturation, while guaranteeing low computational burden and reduced performance impairment(the latter goal, in harmonic compensation context, leads to rather non-standard problem formulation).To this aim, the anti-windup acts on the current references through a suitably-designed additional dynamics. Then, in order to cope with current limitations, an additional strategy has been designed; again the current references is suitably shaped to comply with the features and bounds of the system, augmented with the above-mentioned anti-windup solution. The proposed scheme can be simply joined to any kind of unconstrained controller adopted to steer Shunt Active Filters. In this work, an Internal-Model-based current controller is adopted as a benchmark case. The proposed approach is validate through extensive simulation tests.

Rapid transaction to load variations of active filter supplied by PV system

This paper deals with the analysis and control of a photovoltaic （PV） system connected to the main supply through a Boost converter and shunt active filter supplied by a PV system providing continuous supply of nonlinear load in variation. A robust control of a PV system connected to the grid while feeding a variable nonlinear load is developed and highlighted. This development is based on the control of the Boost converter to extract the maximum power from the PV system using the Perturb and Observe （P and O） algorithm in the presence of temperature and illumination. The proposed modeling and control strategy provide power to the variable nonlinear load and facilitates the transfer of power from solar panel to the grid while improving the quality of energy （harmonic currents compensation, power factor compensation and dc bus voltage regulation）. Validation of the developed model and control strategy is conducted using power system simulator Sim-Power System Blockset Matlab/Simulink. To demonstrate the effectiveness of the shunt active filter to load changes, the method of instantaneous power （pq theory） is used to identify harmonic currents. The obtained results show an accurate extraction of harmonic currents and perfect compensation of both reactive power and harmonic currents with a lower THD and in accordance with the IEEE-519 standard.