Single-phase Active Power Filter Research Articles

Observation and Backstepping Control of Single-Phase Shunt Active Power Filter Connected to photovoltaic System.

The present paper concentrates on the improvement of power quality using a single-phase active power filter (APF) connected to the photovoltaic (PV) array operating in the presence of a non-linear load. A novel controller design, based on the energy stored in the half-bridge shunt APF is proposed to ensure two main objectives at the same time: (i) the transfer of active power to the electrical network by extracting the maximum of active power from the PV panels and regulating the PV voltage to a reference value provided by the MPPT; (ii) the improvement of power factor correction (PFC) by compensating for the harmonic current and reactive power produced by the non-linear load using the backstepping technique and Lyapunov tools. The nonlinear controller is developed in two loops. An inner loop is constituted of a PFC regulator based on the energy stored in the APF to minimize the total harmonic distortion (THD). An outer loop uses a linear PI regulator to regulate PV array voltage. The controller also comprised an observer to estimate the voltage network, which is not accessible to measurements. The performance of the proposed controller is validated by simulation using MATLAB/Simulink.

Self-Feedback Neural Network Sliding Mode Control With Extended State Observer for Active Power Filter

In this paper, a fuzzy neural network adaptive sliding mode control with a self-feedback recursion (FNNASMCSFR) based linear extended state observer (LESO) is proposed for a single-phase active power filter (APF), where the adaptive sliding mode controller is designed to improve the response and accuracy of current compensation and reference current tracking. The LESO is designed to estimate the actual APF system dynamics which includes the parameter perturbation and external disturbance. Moreover, the fuzzy neural network with self-feedback recursion is adopted to mimic the switching control gain of ASMC, which combines the output values of neurons at the current time and the previous time, to achieve better dynamic approximation effect and prevent sudden changes. Simulation and hardware experiments verify the introduced method is a viable control solution in harmonics suppression and current control.

Finite-Time Disturbance Observer of Active Power Filter With Dynamic Terminal Sliding Mode Controller

This article proposes an adaptive dynamic terminal sliding mode control (ADTSMC) based on a finite-time disturbance observer (FTDO) for a single-phase active power filter (APF). Aiming at the internal parameter fluctuations and external unknown disturbances in the APF system, an FTDO is designed to compensate for the unknown uncertainties. Then, the proposed dynamic terminal sliding mode control (DTSMC) method combines the dynamic sliding mode control and the terminal sliding mode control to achieve finite-time convergence and weaken system chattering. In order to ensure the organic combination of FTDO and DTSMC, a dual-hidden-layer recurrent neural network (DHLRNN) is used to estimate the gain of sliding mode switching term adaptively so that FTDO can achieve the maximum disturbance estimation. Hardware experiments verify that the designed ADTSMC method has satisfactory robustness and harmonic compensation property under different nonlinear loads.

A modified indirect extraction method for a single-phase shunt active power filter with smaller DC-link capacitor size

Indirect extraction method is the most common method to control the single-phase active power filters (APFs) due to its simple structure. The main drawback of this extraction method is its performance dependency on the quality of the DC-link voltage. Selecting the high capacity of the DC-link capacitor leads to the high cost and size of APF, weak dynamic response and low-even-order harmonic components on the DC-link voltage. The low capacity of the DC-link capacitor decreases the cost and size of APF, decreases the sub-harmonics and inter-harmonics of the DC-link voltage, improves the dynamic response, and increases the even-order voltage harmonics. This paper proposes a new extraction method to improve the performance of the conventional indirect extraction method. The proposed method uses a small size of capacitor to achieve the aforementioned advantages. The even-order voltage harmonics are eliminated by the single-frequency-decoupled (SFD) scheme. For implementation of the SFD scheme, the proposed method uses proportional-resonant (PR) controllers, and second order generation integrator-frequency locked loop (SOGI-FLL). The effectiveness of the proposed extraction method is verified by the simulation and experiment.

Fuzzy Multiple Hidden Layer Neural Sliding Mode Control of Active Power Filter With Multiple Feedback Loop

A fuzzy multiple hidden layer neural sliding mode control with multiple feedback loop (FMHLNSMCMFL) is proposed for a single-phase active power filter (APF), where a sliding mode controller is designed to make the current tracking error converge to zero and a new neural network with multiple feedback loops is introduced to approximate unknown dynamics. At the same time, the fuzzy neural network can eliminate chattering, improve the control accuracy and reduce the current distortion rate of APF. Moreover, the proposed double feedback fuzzy double hidden layer recurrent neural network is the weighted sum of fuzzy network and double hidden layer network and has strong global learning ability. The adaptive parameters obtained by Lyapunov function can ensure the asymptotic stability of the system. Simulation and hardware experiments verify the introduced FMHLNSMCMFL scheme is a viable control solution for the APF.

Single-Phase Active Impedance Based Harmonic and Reactive Compensation

Single-phase active impedance hybrid active power filter is design to mitigate harmonic and reactive caused by the ever-increasing nonlinear loads. Nonlinear loads have been increased in residential and commercial as well as industrial sectors. Single-phase nonlinear loads contribute a harmonics and low power factor for the power systems. Single-phase active impedance hybrid active power filter was investigated to actively adjust multiple active short circuits. The dominant load current harmonics are compensated due to its multiple short effects over the single-tuned LC filter. At the same time, the conservative power theory (CPT) base reactive current extraction method was applied to actively regulate the reactive power. The amount of the fundamental filter reactive current obtained from CPT determines the reactive power compensation. The results were analyzed and presented in collaboration with the MATLAB/Simulink environment and TMS320F28335 board. The active impedance and CPT based control achieved a harmonic compensation (from 65.96% to 3.20%) and power factor correction from 0.85 to 0.95. Therefore, the active impedance hybrid active power filter can be taken as a good candidate for harmonic and reactive compensation with extending the conventional hybrid active power filter (HAPF) into multiple active tuned filters. It has potential practical benefit to avoid regular field retuning the passive filter in the industry. Moreover, it can also apply for PQ compensation using the existing PPF.

Fuzzy Double Hidden Layer Recurrent Neural Terminal Sliding Mode Control of Single-Phase Active Power Filter

This article focuses on the design of a terminal sliding mode control (TSMC) using a fuzzy double hidden layer recurrent neural network (FDHLRNN) strategy for a single-phase active power filter (APF). A TSMC is proposed to make the tracking error of the system converge to zero in a finite time. An FDHLRNN is proposed and applied in harmonic suppression to approximate the equivalent control and eliminate the unknown disturbance, reducing the role of symbol switching items. The main function of the FDHLRNN is to improve control accuracy and reduce the current distortion rate of the APF. The designed FDHLRNN is the weighted sum of the fuzzy network and the double hidden layer network, having a strong global learning ability. The adaptive parameters of the FDHLRNN are derived by the Lyapunov function to ensure the asymptotic stability of the system. The compensation performance and effectiveness of the proposed TSMC using FDHLRNN strategy are verified by real-time experiments.

Research on three-phase four-wire active power filter based on LCLCL coupling structure

In this paper, the main circuit topology of the three-phase four-wire active power filter (APF) and its harmonic current detection and control algorithm are studied. An active power filter system combining LCLCL filter and a three-phase H-bridge structure is proposed. This paper has applied harmonic detection algorithm based on an improved synchronous phase-locked loop (SRF-PLL) and recursive discrete Fourier transform (RDFT) while using triangular carrier modulation control based on PI adjustment to realize the harmonic compensation of the power filter to the grid current. The system has a notch effect on the harmonic at the switching frequency. It can detect the fundamental component and each harmonic component of the load current separately with a small amount of calculation, good real-time performance. Finally, a 5KVA single-phase APF prototype was built to test the superiority of the main circuit topology and the algorithm of current detection and control.

Dynamic Terminal Sliding-Mode Control for Single-Phase Active Power Filter Using New Feedback Recurrent Neural Network

In this article, an adaptive dynamic terminal sliding-mode controller using a double hidden layer recurrent neural network (DHL-RNN) structure for a single-phase active power filter (APF) is proposed to improve harmonic compensation performance. First, a method combining dynamic sliding mode and terminal sliding mode is proposed to solve the chattering phenomenon in traditional sliding-mode control. Then, since the nonlinear dynamics of APF is difficult to obtain accurately, the DHL-RNN is used to approximate the proposed dynamic terminal sliding-mode controller. Meanwhile, an integral robust switching term is added to eliminate the approximation error of the neural network. Simulation and experimental results proved that the proposed controller has better compensation performance and tracking effect compared with a simple terminal sliding-mode controller.

Model predictive control for single phase active power filter using modified packed U-cell (MPUC5) converter

In this paper, a modified packed U-cell five-level inverter (MPUC5) with Model predictive control (MPC) strategy is proposed for a single phase active power filter (APF) application, which is applied to eliminate harmonic current and compensate reactive power at the point of common coupling (PCC), caused by local non-linear loads connected to the grid. The MPUC inverter configuration consists of numerous DC-link capacitors which should be balanced. In this context, a new model predictive control (MPC) has been designed and implemented to ensure the voltage balancing for the DC-link capacitors, and generate five-level voltage by using six active switches in addition to inject a harmonic current into the grid. For APF application, the inverter should be able to provide the requested reactive power at the PCC and ensure high power factor correction. In order to examine and evaluate the performance of the proposed MPC technique for APF application using 5-level MPUC inverter, a complete simulation model is developed using Matlab/Simulink™ environment and verified through real-time hardware in the loop (HIL) system. The obtained results prove the good performance of the proposed control technique in terms of DC-link capacitors balancing, harmonic current content and power quality enhancement.

Sensorless Nonlinear Control Strategy of the Single Phase Active Power Filters via Two-time Scale Singular Perturbation Technique

This paper focuses on the problem of controlling single-phase shunt active power filters (APFs) operating in the presence of nonlinear and uncertain loads. The main difficulties when controlling this kind of filter are the existence of a strong non-linearity of the system and state variables inaccessible to measurements. This paper proposes a double-loop cascade controller developed on the basis of the singular perturbation technique in order to meet two main control objectives: (i) the inner-loop is designed to compensate the harmonic and reactive currents absorbed by the nonlinear load enforcing power factor correction; (ii) the outer-loop is synthesized to regulate the inverter output capacitor voltage. The controller also includes two-time scale sliding mode observer to estimate the network voltage that is not accessible to measurement. In this work, the singular perturbation technique and averaging theory are used for a complete and rigorous formal analysis to describe the control system performances. The effectiveness of this approach has been successfully verified through computer simulations using the Matlab/Simulink environment.

Energy management and power quality enhancement in grid‐tied single‐phase PV system using modified PUC converter

Pack U-Cell (PUC) multi-level inverter is an attractive topology which widely investigated in the past few years for renewable energy conversion systems. This study introduces a modified five-level packed Unit-cell converter (MPUC5) for single-phase double stage grid-tied photovoltaic (PV) system with unity power factor. The proposed system operates as a single-phase active power filter able to compensate reactive power generated by non-linear loads connected to the point of common coupling, feeds the non-linear load by the generated PV power, and injects the extra power into the grid. The MPUC5 inverter has a special topology with two DC-link capacitors and six switches. One DC-link of the inverter is connected to the PV arrays through DC/DC Cuk converter to draw the maximum power. Therefore, finite-control-set model predictive control (FCS-MPC) for such configuration appears as a promising alternative for this inverter to work properly. Where the proposed FCS-MPC algorithm is designed to ensure a high grid current quality, taking into consideration the issue of the capacitor voltages balancing and the switching frequency minimisation. Both simulation results and experimental validation through real-time hardware in the loop system prove the validity and feasibility of the proposed control scheme, regarding PV power management and quality enhancement.

Linear Active Disturbance Rejection Control for DC Side Voltage of Single-Phase Active Power Filters

Active power filter (APF) has become an effective approach to suppress harmonic and compensating the reactive power of a power grid. In this paper, the topological structure of the single-phase APF is T-type three-level which can suppress harmonic. For the traditional dual-loop PI control of APF, the voltage loop has poor disturbance rejection performance and long response time under nonlinear load and load mutation. To eliminate the impact on the reduction of power quality of the power grid, this paper uses a PI control of the current loop and a linear active disturbance rejection control (LADRC) of voltage loop. The first-order LADRC controller, which uses a linear extended state observer (ESO) and a linear state error feedback (SEF), does not depend on an explicit mathematical model of the controlled object. In this paper, a 2kVA experimental prototype with a processor of TMS320F28335 is designed to testify the performance and effectiveness of the presented method. The results of simulation and experiments show that the LADRC has better disturbance rejection performance and faster dynamic response than PI control under nonlinear load and load mutation.

Design of H∞ control for single-phase active power filter

ABSTRACTIn this work, an output feedback controller is designed based on H-infinity control theory to reduce the influence of parameter perturbation on the performance and robustness of active filters. The designed controller maintained the power current distortion rate below 2.9%, thus guaranteeing the stability of the active filter when parameter perturbation occurred. The simulation results demonstrated the new controller’s improved compensation performance and robustness compared to traditional hysteresis control.

Analysis and experimental validation of a controller for a single-phase active power filter based on a 3L-NPC topology

Summary In this paper, a controller for a shunt active power filter based on a 3-level neutral point clamped inverter is presented. The proposed controller guarantees compensation of harmonic and reactive powers caused by nonlinear loads connected at the point of common coupling. The controller comprises three control loops, namely, a current tracking loop, a voltage regulation loop, and a voltage balance loop. The current tracking loop is aimed to inject the appropriate current by means of the power inverter to compensate reactive power and harmonic distortion assuring a power factor close to unity. The voltage regulation loop is designed to assure that the DC-link reaches a desired constant voltage level, while the voltage balance loop is aimed to regulate each capacitor voltage on the DC-link towards the same voltage value. The performance of the proposed controller is experimentally validated on a 1 kW prototype.

Shunt active power filter-based approach for arc fault detection

In this paper, we present a novel method based on a single-phase active power filter (APF) for series arc faults detection in an AC electrical installation. The APF's reference current is used as the starting point for our method tested on a large variety of loads: resistors, vacuum cleaner, rotary drill, dimmer and AC-DC power supplies. Firstly, the proposed method is validated at the simulation level using the Matlab software and then experimentally using the Hardware-In-the-Loop (HIL) approach with an FPGA Altera Stratix III prototyping board. The results obtained in this work show that series arc faults can be successfully detected with an APF, only by updating its digital control with the arc fault detection functionality, instead of designing from the very beginning an arc-fault detection specific device.

Reduced-rating Hybrid Active Power Filter Comprising Zero-sequence Transformer and Three-phase Three-wire Active Power Filter for Three-phase Four-wire Distribution System

A three-phase four-wire active power filter is proposed in this article that consists of a three-phase three-wire active power filter, zero-sequence transformer, and single-phase active power filter. The reference current for tracking the desired source current is based on the neural network (constraint anti-Hebbian rule algorithm). The three-phase three-wire active power filter compensates current harmonics and reactive power requirement of the non-linear load. A zero-sequence transformer and single-phase active power filter are used to mitigate the neutral current. The proposed hybrid scheme (three-phase four-wire active power filter) significantly reduces the volt–ampere rating of the active power filter and improves the performance under different utility voltage conditions. The simulation of the proposed three-phase four-wire active active power filter is carried out for different voltage conditions. Further, the MATLAB-simulated (The MathWorks, Natick, Massachusetts, USA) response of the three-phase four-wire active active power filter has been validated on a prototype of the three-phase four-wire active-active power filter. The experimental result obtained from the prototype verifies the effectiveness and viability of the proposed scheme.

The use of p-q control in single-phase active power filter for dynamic reactive power compensation

The subject of the discussion is the use of single-phase active filter for compensating dynamic changes of reactive power which may occur in office buildings. This circuit consumes reactive power with high dynamic changes at the level of minutes or seconds and fractions of seconds, making it impossible to efficiently compensate reactive power with standard capacitors-based compensators. Modified p-q algorithm was used to control single-phase active power filter. The considerations were supported by simulations carried out in MATLAB-Simulink environment. Streszczenie. Przedmiotem rozwazan jest zastosowanie 1-fazowego filtru aktywnego do kompensacji dynamicznych zmian mocy biernej jakie mogą wystąpic w przypadku odbiorow w budynkach biurowych. Do sterowania 1-fazowym filtrem aktywnym zostanie wykorzystany algorytm p-q. Rozwazania zostaly parte symulacjami przeprowadzonymi w środowisku MATLAB-Simulink. (Zastosowanie sterowania p-q w 1-fazowym energetycznym filtrze aktywnym do dynamicznej kompensacji mocy biernej).

Novel control structure of single-phase active power filter using recursive least squares estimator considering a distorted environment

In this paper, a new reactive power and harmonic compensation procedure based on the variable forgetting factor-recursive least squares (VFF-RLS) estimator and new phase-locked loop is proposed. For this purpose, the fundamental harmonic component of load current is estimated with VFF-RLS. Independence on order and amplitude of harmonics, fast dynamic and high accuracy are the remarkable features of the designed estimator. As in the case of load changes, the sag/swell and phase jump in grid voltage, optimal compensation is performed in less than half a cycle with a low total harmonic distortion value. In addition, to compensate for an infected power system by varied frequency, a second-order general integrator-frequency-locked loop (SOGI-FLL) control system based on wavelet transform (WT) has been proposed. This phase detector can track the reference phase of a grid in the best manner in the presence of frequency variations. The effectiveness of the proposed method in a single-phase power system has been validated using both simulation and experimental results.

Robust switched fractional controller for performance improvement of single phase active power filter under unbalanced conditions

A novel controller is proposed to regulate the DC-link voltage of a single phase active power filter (SPAPF). The proposed switched fractional controller (SFC) consists of a conventional PI controller, a fractional order PI (FO-PI) controller and a decision maker that switches between them. Commonly, the conventional PI controller is used in regulation loops due to its advantages in steady-state but it is limited in transient state. On the other hand, the FO-PI controller overcomes these drawbacks but it causes dramatic degradation in control performances in steady-state because of the fractional calculus theory and the approximation method used to implement this kind of controller. Thus, the purpose of this paper is to switch to the PI controller in steady-state to obtain the best power quality and to switch to the FO-PI controller when external disturbances are detected to guarantee a fast transient state. To investigate the efficiency and accuracy of the SFC considering all robustness tests, an experimental setup has been established. The results of the SFC fulfill the requirements, confirm its high performances in steady and transient states and demonstrate its feasibility and effectiveness. The experiment results have satisfied the limit specified by the IEEE harmonic standard 519.