Active Filter System Research Articles

Evaluation of Interval Type-2 Fuzzy Neural Super-Twisting Control Applied to Single-Phase Active Power Filters

This research introduces an improved control strategy for an active power filter (APF) system. It utilizes an adaptive super-twisting sliding mode control (STSMC) scheme. The proposed approach integrates an interval type-2 fuzzy neural network with a self-feedback recursive structure (IT2FNN-SFR) to enhance the overall performance of the APF system. The IT2FNN with STSMC proposed here consists of two components, with one being IT2FNN-SFR, which demonstrates robustness for uncertain systems and the ability to utilize historical information. The IT2FNN-SFR estimator is used to approximate the unknown nonlinear function within the APF. Simultaneously, the STSMC component is integrated to reduce system chattering, improving control precision and overall system performance. STSMC combines the robustness and simplicity of traditional sliding mode control, effectively addressing the chattering problem. To mitigate inaccuracies and complexities associated with manual parameter setting, an adaptive law of sliding mode gain is formulated to achieve optimal gain solutions. This adaptive law is designed within the STSMC framework, facilitating parameter optimization. Experimental validation is conducted to verify the harmonic suppression capability of the control strategy. The THD corresponding to the designed control algorithm is 4.16%, which is improved by 1.24% and 0.55% compared to ASMC and STSMC, respectively, which is below the international standard requirement of 5%. Similarly, the designed controller also demonstrates advantages in dynamic performance: when the load decreases, it is 4.72%, outperforming ASMC and STSMC by 1.15% and 0.38%, respectively; when the load increases, it is 3.87%, surpassing ASMC and STSMC by 1.07% and 0.36%, respectively.

NOUVEAU FILTRE DE PUISSANCE ACTIVE SHUNT BASÉ SUR UN ONDULEUR NPC À NEUF NIVEAUX UTILISANT LA STRATÉGIE DE MODULATION MC-LSPWM

This paper presents a novel shunt active power filter (Shunt APF) system based on a nine-level neutral point clamped (NPC) inverter, which can reduce current harmonics under various nonlinear loads. These loads can introduce harmonic currents within the system, which causes excessive power losses and alters the voltage systems' characteristics. Today, multi-level inverters are more suitable for high-voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. The reference signals required to compensate harmonic currents use the synchronous detection method (SDM) with phase disposition sinusoidal pulse width modulation (PD-SPWM) control due to its low complexity and superior performance. The proposed shunt APF configuration simulation is evaluated using MATLAB-Simulink and SimPowerSystem environment with inductive and capacitive non-linear loads. The simulation results show the efficiency of the proposed shunt APF in terms of harmonic compensation and power quality improvement. The results of comparative studies with other less multi-level inverters confirm the superiority of the proposed shunt APF system.

Control Scheme Influence on the Performance of Shunt Active Power Filter based on Five-level NPC Inverter in Steady and Transient Conditions

This paper presents an investigation on the performance of shunt active power filter (Shunt APF) systems based on five-level neural point clamped (NPC) inverter in steady and transient conditions adopting a fuzzy control scheme. The shunt APF is operated as a current source connected in parallel with the non-linear loads to inject compensates current harmonics into the AC source. The multi-level inverters have gained considerable interests in last year’s. Five-level inverter is recommended in medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, low voltage stress of power semiconductors and low acoustic noise. Secondly fuzzy logic has been widely used in various industrial applications. To benefit from these advantages a shunt active power filter based on five-level (NPC) inverter using fuzzy control scheme is presented in this work. To identify the reference currents, synchronous detection method (SMD) is adopted. Proportional integral voltage controller is used to maintain the dc voltage across capacitor constant and reduce inverter losses. The simulation is performed using MATLAB-Simulink software and SIMPOWERSYSTEM toolbox. The obtained results in steady and transient states illustrate the performances and the effectiveness of the proposed shunt APF system.

Impact of Converter Topology on the Shunt Active Power Filter Systems Efficiency

This paper presents the performance of shunt active power filters (Shunt APFs) which can compensate harmonic currents generated by no-linear load based on five and seven-level neural point clamped (NPC) inverters. Multilevel inverters are currently being investigated and used in several industrial applications. Their advantages include the capability to reduce the harmonic content and decrease the voltage or current ratings of the semiconductors. On the other side, fuzzy techniques are successfully employed in various industrial applications; they represent a good alternative to traditional control systems. To benefit of all these advantages an efficient control scheme for five and seven-level Shunt APF based on multi-carrier pulse width modulation (MC-PWM) and fuzzy control approaches are adopted in this work. The fuzzy controller is designed to improve compensation capability of shunt APF by adjusting the error using a fuzzy rule. The control strategy to identify the current reference uses synchronous detection method (SMD), this technique is easy to implement and achieves good performances. The numerical simulation results carried with MATLAB-Simulink and SimPowerSystems Toolbox show the effectiveness of the proposed systems and confirm the superiority of the seven-level shunt APF compared to five-level configuration system.

Modelling, Simulation and Implementation on dSpace 1103 of the Direct Power Control in a Three-Phase Shunt Active Power Filter System

This article describes a control method called "direct power control" designed specifically for parallel active power filters. The purpose of this method is to attenuate harmonics in the supply current and offset reactive power problems. The main goal is to bring the active power and reactive power back to the reference values through hysteresis control. The output of the hysteresis controller is combined with the switching table to regulate active and reactive power in real time by determining the optimal switching configuration of the inverter. This study proposes a novel switching table design based on analyzing the impact of the inverter switching vector on the instantaneous reactive and active power derivatives. The goal is to reduce the number of commutations by eliminating zero vectors while maintaining the required DC bus voltage using anti-windup techniques based on PI controllers.

Adaptive Super-Twisting Sliding Mode Control of Active Power Filter Using Interval Type-2-Fuzzy Neural Networks

Aiming at the unknown uncertainty of an active power filter system in practical operation, combining the advantages of self-feedback structure, interval type-2 fuzzy neural network, and super-twisting sliding mode, an adaptive super-twisting sliding mode control method of interval type-2 fuzzy neural network with self-feedback recursive structure (IT2FNN-SFR STSMC) is proposed in this paper. IT2FNN has an uncertain membership function, which can enhance the nonlinear ability and robustness of the network. The historical information will be stored and utilized by the self-feedback recursive structure (SFR) at runtime. Therefore, the novel IT2FNN-SFR is designed to improve the dynamic approximation effect of the neural network and reduce the dependence of the controller on the actual mathematical model. The adaptive rate of each weight of the neural network is designed by the Lyapunov method and gradient descent (GD) algorithm to ensure the convergence and stability of the system. Super-twisting sliding mode control (STSMC) has strong robustness, which can effectively reduce system chattering, and improve control accuracy and system performance. The gain of the integral term in the STSMC is set as a constant, and the other gain is changed adaptively whose adaptive rate is deduced through the stability proof of the neural network, which greatly reduces the difficulty of parameter adjustment. The harmonic suppression ability of the designed control strategy is verified by simulation experiments.

Feature Selection Fuzzy Neural Network Super-Twisting Harmonic Control

This paper provides a multi-feedback feature selection fuzzy neural network (MFFSFNN) based on super-twisting sliding mode control (STSMC), aiming at compensating for current distortion and solving the harmonic current problem in an active power filter (APF) system. A feature selection layer is added to an output feedback neural network to attach the characteristics of signal filtering to the neural network. MFFSFNN, with the designed feedback loops and hidden layer, has the advantages of signal judging, filtering, and feedback. Signal filtering can choose valuable signals to deal with lumped uncertainties, and signal feedback can expand the learning dimension to improve the approximation accuracy. The STSMC, as a compensator with adaptive gains, helps to stabilize the compensation current. An experimental study is implemented to prove the effectiveness and superiority of the proposed controller.

A Novel Control Scheme Using UAPF in an Integrated PV Grid-Tied System

This article investigates the photovoltaic fed universal active power filter (PV-UAPF) system for enhancing power quality indices. A novel comb filter together with second-order generalized integrator (CFSOGI) based instantaneous power balance theory with power angle (IPBTPA) control scheme is implemented. Under distorted or adverse grid conditions, the CFSOGI effectively extracts the phase angle, frequency, and fundamental positive and negative sequence components (FPNSC) to overcome the limitations of adaptive notch filters. Here, a comb filter constitutes a cluster/group of zeros at multiple harmonic frequencies to achieve notch peaks thereby providing superior harmonic rejection ability. Whereas, IPBTPA generates the reference signals to operate the system at dual compensation strategy with or without solar PV. The power angle is used to extract the desired load voltages under grid voltage fluctuations thereby reducing the burden on the shunt converter. Moreover, the hysteresis controller generates the switching pulses based on the calculation of reference and load powers which improves the dynamic performance by maintaining system power balance and effective DC voltage regulation. Besides, reactive power compensation, suppression of harmonic currents and mitigation of grid voltage fluctuations is also carried out to strengthen the system further. The system is also tested in grid voltage interruption for islanding mode to realize a microgrid system. The overall system performance is also validated using simulation and in a real-time experimental set-up, and results are demonstrated under various conditions.

Active Soil Filter System for Indoor Air Purification in School Classrooms.

An active soil filter system was newly designed and evaluated to obtain a higher removal efficiency of fine particulate matter (PM) for indoor air purification in schools. Unlike passive air purification systems that remove PM using only plant leaves, air purification can be maximized by filtering polluted indoor air directly between the soil particles supporting the plant. The novel system is composed of a composite soil layer and a suction blower that forces outside air into the soil layer. It was found that the air purification performance was improved as the inflow air velocity upstream of the soil is decreased and the soil stacking height increased. The lower the soil moisture, the better the air purification performance. Considering both the classroom environment and the system's energy consumption, it is recommended that the soil stacking height is 150 mm, the soil inflow air velocity is 2 cm/s, and the relative humidity is 35%. Under these conditions, the air purification efficiency for PM2.5 is 41.5%. The indoor air purification system using the soil filter system, along with the currently used plant leaves medium, is expected to improve the indoor air quality in public facilities, such as school classrooms.

Greywater Characterization and Treatment Using Chemical Coagulation

The main problem in treating grey water is the large variation in quality observed over short timescales. Different treatment schemes have been used such as physical, chemical and biological processes to treat this effluent. However they have some problems like adjusting shock loading of organic matters and chemicals. Therefore, in the present study chemical coagulation process was tested to treat grey water. Coagulants (alum and ferric chloride) were used in the present work to treat both real and synthetic grey water. The findings showed that at a dose of 30 mg/L of ferric chloride, 90% of the solution's turbidity and 80% of the TDS could consistently be removed. These findings were well matched with biological active filter system that reported 85% of COD removal from grey water. In addition, the effects of pH and alkalinity on the removal performance were also investigated. Overall, the present study showed that both traditional and proposed novel chemical process could treat grey water to the required level which can further be re-used for agricultural activities.

Extended State Observer Based Interval Type-2 Fuzzy Neural Network Sliding Mode Control With Its Application in Active Power Filter

Aiming at the difficulties in modeling the active power filter (APF) system and the susceptibility to parameter perturbation and external disturbance, this article proposes a new adaptive sliding mode controller with using a nonlinear extended state observer (NESO) based on an interval type-2 fuzzy neural network (IT2FNN) structure. The IT2FNN is designed to estimate the unknown control coefficient, so that the NESO can estimate the state of the system and the total disturbance including the unmodeled dynamics and external disturbances, and then perform feedforward compensation to achieve active disturbance rejection. Simulation and experimental results show that the proposed control strategy is effective in the harmonic suppression of the APF system and has better steady-state and dynamic performance compared with the existing methods.

Research on Oscillation Suppression Methods in Shunt Active Power Filter System

The shunt active power filter (SAPF) system oscillation is a massive threat to the security and stability of the power grid. This study classifies SAPF oscillation into two categories according to the difference in mechanisms. The SAPF oscillation in one category is caused by the resonant characteristics of a switching noise filter and is called external loop amplification. The SAPF oscillation in the other category is induced by the presence of a capacitor in the load current for SAPF and is called self-excited oscillation. Unlike previous studies, this study tried to reveal the internal relationship between the two kinds of SAPF oscillation, present a general shunt virtual-damping-based SAPF oscillation suppression strategy covering the previous resonant damping method, and provide the discrete domain stability criterion of the control system. The sampling frequency was at least six times the resonant frequency. The stability region was enlarged with an increase in the sampling frequency and narrowed with a rise in the resonant frequency. As to the harmful self-excited oscillation problem, this study proposes a composite control strategy combining selective harmonic compensation and grid-side current feedback. Moreover, this study considers the more general resistance–inductance–capacitance load situations and analyzes the stability of the SAPF–Thyristor Switched Capacitor (TSC) hybrid compensation system. Simulations and experiments demonstrated that the proposed compound control method can reduce the primary harmonics of the system by more than 90% and has a better oscillation suppression performance than previous suppression methods. In particular, if we selected the TSC series reactance rate following more than 6%, self-excited oscillation could usually be avoided.

Adaptive Intelligent Sliding Mode Control of a Dynamic System with a Long Short-Term Memory Structure

In this work, a novel fuzzy neural network (NFNN) with a long short-term memory (LSTM) structure was derived and an adaptive sliding mode controller, using NFNN (ASMC-NFNN), was developed for a class of nonlinear systems. Aimed at the unknown uncertainties in nonlinear systems, an NFNN was designed to estimate unknown uncertainties, which combined the advantages of fuzzy systems and neural networks, and also introduced a special LSTM recursive structure. The special three gating units in the LSTM structure enabled it to have selective forgetting and memory mechanisms, which could make full use of historical information, and have a stronger ability to learn and estimate unknown uncertainties than general recurrent neural networks. The Lyapunov stability rule guaranteed the parameter convergence of the neural network and system stability. Finally, research into a simulation of an active power filter system showed that the proposed new algorithm had better static and dynamic properties and robustness compared with a sliding controller that uses a recurrent fuzzy neural network (RFNN).

3상 3선 전력 시스템에 적용된 순시전력이론의 α-β전력 및 전류성분에 관한 실험적 고찰

This study experimentally derives various power and current components at α-β coordinates from instantaneous power theory applied to voltage-type nonlinear loads. An induction motor drive system is used as a voltage-type nonlinear load, and a simulated active power filter system based on DSP(Digital Signal Processor) is manufactured to verify its validity experimentally. Each power and current component of an induction motor driving 3-phase 3-wire power system is calculated with DSP to implement a simulated active power filter, and from this result, a flow of instantaneous compensation power could be experimentally verified. When various current and power components derived from instantaneous power theory are used as control reference signals of a simulated active power filter, the effect on a voltage-type nonlinear load current is experimentally investigated.

Shunt Active Power Filter Performances based on Seven-level NPC Inverter using Fuzzy and LS-PWM Control Scheme

This paper presents novel seven-level neutral point clamped (npc) shunt active power filter system based on LS-PWM and fuzzy control approaches which can eliminate current harmonics generated by nonlinear loads. Today, multi-level inverters are strongly used in the medium and high voltage applications; their advantages are low harmonic distortions, low switching losses, low electromagnetic interference, and low acoustic noise. Second, fuzzy logic techniques have been successfully employed in several power electronic applications. Fuzzy controller does not need an accurate mathematical model, can work with imprecise inputs, can handle non-linearity, and are more robust than conventional controllers. To benefit from these advantages a novel control scheme for seven-level (npc) inverter based on Fuzzy and LS-PWM technique is proposed. The reference current signals required to compensate harmonic currents use the synchronous current detection method, this technique is easy to implement and achieves good performances for harmonic compensation. The proposed shunt APF is evaluated using Matlab-Simulink software and SimPowerSystem Toolbox under transient and steady state for various operation conditions. The simulation results show the effectiveness of the proposed shunt active filter based on seven-level (NPC) inverter for improving the power quality and the superiority of combined fuzzy and LS-PWM control scheme to conventional controller in term of harmonics compensation and dynamic performances.

An Inductive Active Filtering Method for Low-Voltage Distribution Networks

Three-phase unbalanced and nonlinear loads aggravate harmonic problems in low-voltage distribution networks. In this paper, a hybrid inductive and active filter (HIAF) system with a Ddy converter transformer is proposed. By establishing the circuit and corresponding mathematical models, the working mechanism of the HIAF system in harmonic suppression is analyzed. In the designed HIAF system, we install the detection point on the grid-side winding and the compensation point on the filtering winding. Since both windings have the same connection, no phase compensation between the harmonic detection point and compensation point is demanded. Eventually, we apply a harmonic damping control and zero-value impedance control strategy to realize harmonic suppression under both balanced and unbalanced loads. The simulation results show that the HIAF system can effectively suppress harmonics under various load conditions.

An integrated active biochar filter and capacitive deionization system for high-performance removal of arsenic from groundwater

An integrated process of filtration and electrosorption was first applied to enable high-performance arsenic removal for groundwater remediation. An active manganese dioxide-rice husk biochar composite (active BC) filter was utilized for oxidization of As(III) to As(V) and initial removal of As(III, V). Subsequently, electrosorption by capacitive deionization (CDI) was applied as a posttreatment to improve arsenic removal. The active BC approach exhibited fast removal rates of 0.75 and 0.63 g mg–1 h–1 and high maximum removal capacities of 40.76 and 48.15 mg g–1 for As(III) and As(V), respectively. Importantly, column experiments demonstrated that the arsenic removal capacity in the active BC filter was 2.88 mg g–1, which was 72 times higher than that of BC. The results were due to the high efficiency (94%) of redox transformation of As(III) to As(V). The electrosorptive removal of arsenic was further controlled by changing the voltage in CDI. With a charging step of 1.2 V, the total arsenic concentration can be reduced to 0.001 mg L–1 with a low energy consumption of 0.0066 kW h m−3. Furthermore, the integrated system can remove As from real groundwater to achieve the World Health Organization guideline value for drinking water quality.

Optimal Hybrid Filtering Strategy Using Adaptive Genetic-Fuzzy Logic Control for Harmonics Reduction in a Standalone Micro Hydroelectric Power Plant Coordinated with a PV System

Micro Hydro Power Plants are a type of power production that uses the force of river flows or waterfalls to generate electricity. The generator generates current waves and harmonic voltage, which are distorted wave disturbances that cause fundamental frequency multiplication. The major goal of this work is to design a reliable, efficient, and innovative harmonic mitigation approach for a stand-alone micro hydroelectric system that is coordinated with a photovoltaic renewable energy system utilising an active power filter. We may pick the active filter highest harmonic to be suppressed using the magnitude information supplied for each harmonic component. A hybrid filtering approach to remove harmonics and a novel MOGA optimization technique are part of the suggested harmonics reduction solution. The goal of this article is to determine the optimum filter for decreasing harmonics in an induction generator. As the harmonic damper, two filters were chosen: a passive filter and an active power filter. The suggested MOGA control method is compared to GA and evaluated on simulated data. In tracking harmonic components and fundamental frequency, the suggested MOGA control system provides high convergence speed and accuracy. It's extremely adaptable, and it can predict changes in the phase angle, amplitude, and fundamental frequency of harmonic components. When compared to the Genetic Algorithm method, it performs better. Simulation results using the SIMULINK/MATLAB simulation tool are delivered to evaluate the efficacy of the suggested active filter system. The impact of harmonic currents on the magnetic flux density is investigated using the rated condition as a reference. It has been established that the time harmonic is a significant element influencing generator performance. At the same time, the impacts of harmonic currents on the generator's eddy current loss, average torque, and torque ripple are investigated, as well as the mechanism of eddy current loss fluctuation.

Distribution system power quality compensation using a HSeAPF based on SRF and SMC features

The purpose of this paper is to describe the design of a Hybrid Series Active Power Filter (HSeAPF) system to improve the quality of power on three-phase power distribution grids. The system controls are comprise of Pulse Width Modulation (PWM) based on the Synchronous Reference Frame (SRF) theory, and supported by Phase Locked Loop (PLL) for generating the switching pulses to control a Voltage Source Converter (VSC). The DC link voltage is controlled by Non-Linear Sliding Mode Control (SMC) for faster response and to ensure that it is maintained at a constant value. When this voltage is compared with Proportional Integral (PI), then the improvements made can be shown. The function of HSeAPF control is to eliminate voltage fluctuations, voltage swell/sag, and prevent voltage/current harmonics are produced by both non-linear loads and small inverters connected to the distribution network. A digital Phase Locked Loop that generates frequencies and an oscillating phase-locked output signal controls the voltage. The results from the simulation indicate that the HSeAPF can effectively suppress the dynamic and harmonic reactive power compensation system. Also, the distribution network has a low Total Harmonic Distortion (< 5%), demonstrating that the designed system is efficient, which is an essential requirement when it comes to the IEEE-519 and IEC 61,000–3-6 standards.

A fault tolerance method based on switch redundancy for shunt active power filter

In order to improve the reliability of the shunt active power filter(SAPF) system, the fault-tolerant control strategy of the system is studied in this paper. A fault-tolerant control strategy based on improved switch redundancy is designed inside SAPF system, and fault-tolerant is achieved through circuit reconstruction. Then the operating mode and voltage vector characteristics of the fault-tolerant topology are analyzed, and the corresponding SVPWM control algorithm is derived. Finally, experiments verify the practicability and effectiveness of the SAPF fault-tolerant control method proposed in this paper.