Operation Of Shunt Active Power Filter Research Articles

Hybrid One-Cycle-PI Control Algorithm for Shunt Active Power Filter in Mitigating Harmonic Currents

The quality of current waveforms, such as the presence of the harmonic components at the point of common coupling of various consumers, deteriorated due to the nonlinear load applications. Hence, a Shunt Active Power Filter (SAPF) is used to mitigate harmonic pollution in an electrical network. The heart of the SAPF operation is the current control technique. The choice of current control techniques significantly impacts the SAPF performance. As a result, a Hybrid One-Cycle-PI Control (HOCPIC) is proposed to work as a single-phase SAPF's current controller. The HOCPIC utilises a Proportional-Integral (PI) controller to minimise the error signal. As a result, the THD value of the supply current is reduced to 3.20% using the SAPF-based HOCPIC compared to 3.99% when using the SAPF-based OCC. The result proves that the SAPF-based HOCPIC performs better in compensating harmonic currents than the SAPF-based OCC.

Modified CCF Based Shunt Active Power Filter Operation With Dead-Band Elimination for Effective Harmonic and Unbalance Compensation in 3-Phase 3-Wire System

The effect of reduction in the terminal voltage of a grid-tied inverter together with minimization in total harmonic distortion (THD) of terminal voltage and current, in the presence of dead-band in the switching remains always challenging for the researchers. With high switching frequency, this issue increases by many folds. The grid-tied inverter used for harmonic compensation acts as a shunt active power filter (SAPF). The implementation of the dead-band elimination technique is based on output current polarity detection, suffers from multiple zero-crossing due to the generation of high frequency switching harmonics during SAPF operation. This paper deals with a dead band elimination methodology together with harmonic compensation using SAPF under non-linear and unbalanced loading conditions. Here, SAPF uses a dual fundamental component extraction (DFCE) scheme with modified complex coefficient filter (MCCF) to extract fundamental components for reference current generation to implement an indirect current control PWM scheme. MCCF extracts fundamental components even in the presence of dc offset and unbalancing at the input. For incorporating dead-band elimination in control, exact polarity detection is done separately through SAPF output current estimation using sensed load current, and modified CCF computed reference source current. Since the estimated SAPF output current contains no high-frequency switching harmonics, the dead-band elimination technique can be correctly implemented. To synchronize the zero-crossing of the estimated and actual SAPF current, an adaptive delay control is used. The proposed MCCF based control logic’s performance together with the dead-band elimination technique is validated for SAPF operating under non-linear, unbalance, and dynamic load conditions. The proposed dead-band elimination scheme based SAPF model is developed and simulated using MATLAB/ SIMULINK. The simulation results show a significant reduction in source current harmonics due to the elimination of odd harmonic injection into the system by incorporating dead-band elimination in SAPF operation. The real-time simulation of the proposed method is also validated using OPAL-RT OP4510 real-time platform.

Shunt Active Power Filter: A Review on Phase Synchronization Control Techniques

Owing to the destructive impacts of harmonic currents, the topic of reducing their impacts on power system has attracted tremendous research interests. In this regard, a shunt active power filter (SAPF) is recognized to be the most reliable instrument. It performs by first detecting the harmonic currents that are present in a harmonic-contaminated power system, and subsequently generates and injects corrective mitigation current back into the power system to cancel out all the detected harmonic currents. This means that other than the ability to generate corrective mitigation current itself, it is actually more important to make sure that the SAPF is able to operate in phase with the operating power system, so that the mitigation current can correctly be injected. Hence, proper synchronization technique needs to be integrated when designing the control algorithms of SAPF. This paper critically discusses and analyzes various types of existing phase synchronization techniques which have been applied to manage operation of SAPF; in terms of features, working principle, implementation and performance. The analysis provided can potentially serve as a guideline and provision of information on selecting the most suitable technique for synchronizing SAPF with the connected power system.

Mathematical and Experimental Investigation on Advanced PLL for Cascaded H-Bridge Multilevel Inverter in Active Filtering Application

Cascaded H-bridge multilevel inverter (CHB-MLI)-based shunt active power filter (SAPF) is one of the finest solutions for power quality improvement in case of medium-voltage distribution sector. Performance of SAPF degrades due to the presence of DC offset and harmonics in the grid voltage since this will result phase angle and frequency error. Therefore, modified single-phase synchronous reference frame theory comprising of advanced PLL is presented in this article. The advanced PLL can track frequency and phase angle accurately even though source voltage is having DCor harmonic content. A detailed mathematical modeling and stability analysis of this PLL is presented using Routh-Hurwitz criteria. A novel systematic design procedure using gravitational search algorithm (GSA) and an Eigen value analysis is proposed for calculating optimal PLL parameters. Closed-loop SAPF control stability is tested using root-locus analysis. An extensive experimental analysis of the proposed control applied to CHB-MLI-based SAPF has been performed under distorted source voltage and non-linear loading conditions to show the effectiveness of the proposed control over recently published work. Source current maintains its sinusoidal shape, properly synchronized with grid voltage and having distortion limit in compliance with IEEE-519 standard irrespective of source voltage conditions during the operation of SAPF.

A Review on Shunt Active Power Filter Control Strategies

Shunt active power filter (SAPF) has now become a well-known sophisticated technology to overcome current harmonics and reactive power compensation issues. In this paper a technical review of various control strategies for operation of SAPF has been presented. Control strategies such as reference current generation by time domain, frequency domain and soft computing approaches; voltage control for dc link voltage regulation and current control for generating switching patterns for voltage source inverter has been discussed. This paper aims to provide a broad understanding on SAPFs for various research and engineering applications. Â

Operation of Three-Level Inverter-Based Shunt Active Power Filter Under Nonideal Grid Voltage Conditions With Dual Fundamental Component Extraction

In this paper, a new reference current generation method is proposed for effective harmonics mitigation and reactive power compensation of three-level neutral-point diode clamped inverter-based shunt active power filter (SAPF) under nonideal grid voltage conditions. The proposed method is named as dual fundamental component extraction algorithm. In operation, the proposed algorithm extracts at the same time, the desired fundamental current and voltage components for generating reference current and synchronization phases, respectively. As a result, the proposed algorithm is able to generate reference current that ensures in phase operation of SAPF with the operating power system, without depending on any phase-locked loop elements. Besides, the proposed algorithm employs self-tuning filter (STF) for accurate computation of the fundamental components. Design concept and effectiveness of the proposed algorithm are thoroughly studied and evaluated in MATLAB–Simulink. Additionally, a laboratory prototype utilizing TMS320F28335 digital signal processor is built to validate its feasibility. Encouraging findings obtained from both simulation and experimental works demonstrate effectiveness of the proposed algorithm under both ideal and nonideal grid voltage conditions.

A Dual-Function Instantaneous Power Theory for Operation of Three-Level Neutral-Point-Clamped Inverter-Based Shunt Active Power Filter

This paper proposes a simple yet effective reference current generation algorithm based on instantaneous power pq theory to enhance mitigation performance of a three-phase three-level neutral-point-clamped (NPC) inverter-based shunt active power filter (SAPF). The proposed algorithm is developed for dual functionality: generate reference current and synchronization phase to effectively govern operation of SAPF in mitigating harmonic current and compensating reactive power. Three key modifications are implemented: (1) replacement of numerical low-pass filter (LPF) with an average power detector to improve mitigation performance; (2) removal of needless reactive element to reduce algorithm complexity; and (3) integration of phase tracking feature to eliminate the needs of phase-locked loop (PLL). Simulation work of SAPF with the proposed algorithm was conducted and assessed in MATLAB–Simulink. In addition, to verify feasibility of the proposed algorithm, a laboratory prototype as constructed with TMS320F28335 digital signal processor (DSP) programmed as the controller. Performance of SAPF achieved by utilizing the proposed algorithm was thoroughly investigated and benchmarked with that demonstrated using the existing pq theory algorithm to evaluate the inherent advantages. Simulation and experimental results are obtained for different nonlinear loads and test conditions. Responses demonstrated by SAPF in both simulation and experimental works reveal superiority of the proposed algorithm over the existing algorithm.

Control Algorithms of Shunt Active Power Filter for Harmonics Mitigation: A Review

Current harmonics is one of the most significant power quality issues which has attracted tremendous research interest. Shunt active power filter (SAPF) is the best solution to minimize harmonic contamination, but its effectiveness is strictly dependent on how quickly and accurately its control algorithms can perform. This manuscript reviews various types of existing control algorithms which have been employed for controlling operation of SAPF. Harmonic extraction, DC-link capacitor voltage regulation, current control and synchronizer algorithms are examined and discussed. The most relevant techniques which have been applied for each control algorithm are described and contrasted in an organized manner to identify their respective strengths and weaknesses. It is found that the applied control algorithms differ in two conditions: (1) the condition where harmonic current distortion is treated by the SAPF in the presence of non-ideal source voltage; and (2) the condition where multilevel inverter is employed as the circuit topology of SAPF.

Adaptive Hybrid Fuzzy-Proportional Plus Crisp-Integral Current Control Algorithm for Shunt Active Power Filter Operation

An adaptive hybrid fuzzy-proportional plus crisp-integral current control algorithm (CCA) for regulating supply current and enhancing the operation of a shunt active power filter (SAPF) is presented. It introduces a unique integration of fuzzy-proportional (Fuzzy-P) and crisp-integral (Crisp-I) current controllers. The Fuzzy-P current controller is developed to perform gain tuning procedure and proportional control action. This controller inherits the simplest configuration; it is constructed using a single-input single-output fuzzy rule configuration. Thus, an execution of few fuzzy rules is sufficient for the controller’s operation. Furthermore, the fuzzy rule is developed using the relationship of currents only. Hence, it simplifies the controller development. Meanwhile, the Crisp-I current controller is developed to perform integral control action using a controllable gain value; to improve the steady-state control mechanism. The gain value is modified and controlled using the Fuzzy-P current controller’s output variable. Therefore, the gain value will continuously be adjusted at every sample period (or throughout the SAPF operation). The effectiveness of the proposed CCA in regulating supply current is validated in both simulation and experimental work. All results have proven that the SAPF using the proposed CCA is capable to regulate supply current during steady-state and dynamic-state operations. At the same time, the SAPF is able to enhance its operation in compensating harmonic currents and reactive power. Furthermore, the implementation of the proposed CCA has resulted more stable dc-link voltage waveform.

A Wavelet-Based Unified Power Quality Conditioner to Eliminate Wind Turbine Non-Ideality Consequences on Grid-Connected Photovoltaic Systems

The integration of renewable power sources with power grids presents many challenges, such as synchronization with the grid, power quality problems and so on. The shunt active power filter (SAPF) can be a solution to address the issue while suppressing the grid-end current harmonics and distortions. Nonetheless, available SAPFs work somewhat unpredictably in practice. This is attributed to the dependency of the SAPF controller on nonlinear complicated equations and two distorted variables, such as load current and voltage, to produce the current reference. This condition will worsen when the plant includes wind turbines which inherently produce 3rd, 5th, 7th and 11th voltage harmonics. Moreover, the inability of the typical phase locked loop (PLL) used to synchronize the SAPF reference with the power grid also disrupts SAPF operation. This paper proposes an improved synchronous reference frame (SRF) which is equipped with a wavelet-based PLL to control the SAPF, using one variable such as load current. Firstly the fundamental positive sequence of the source voltage, obtained using a wavelet, is used as the input signal of the PLL through an orthogonal signal generator process. Then, the generated orthogonal signals are applied through the SRF-based compensation algorithm to synchronize the SAPF’s reference with power grid. To further force the remained uncompensated grid current harmonics to pass through the SAPF, an improved series filter (SF) equipped with a current harmonic suppression loop is proposed. Concurrent operation of the improved SAPF and SF is coordinated through a unified power quality conditioner (UPQC). The DC-link capacitor of the proposed UPQC, used to interconnect a photovoltaic (PV) system to the power grid, is regulated by an adaptive controller. Matlab/Simulink results confirm that the proposed wavelet-based UPQC results in purely sinusoidal grid-end currents with total harmonic distortion (THD) = 1.29%, which leads to high electrical efficiency of a grid-connected PV system.

Dual Function of Unified Adaptive Linear Neurons Based Fundamental Component Extraction Algorithm for Shunt Active Power Filter Operation

Unified Adaptive Linear Neurons (ADALINEs) based fundamental component extraction algorithm is presented for better operation of a Shunt Active Power Filter (SAPF). The proposed algorithm is developed for dual functionality. The first role is to generate a reference current for the SAPF. Whilst, the second function is to coordinate the phase of the generated reference current with the phase of any operating power system. Consequently, the operation of the SAPF will be synchronized with the operating power system. Hence, it replaces the necessity of using conventional synchronization algorithms such as Phase-Locked Loops (PLLs) and Zero-Crossing Detectors (ZCDs). In this work, the proposed algorithm is executed using an integration of two ADALINEs based fundamental current and voltage extraction algorithms. Also, it implements the modified on-line Widrow-Hoff (W-H) weight updating algorithm for high speed extraction process. The effectiveness of the proposed algorithm has been verified in both simulation and experimental works.

A Simple Algorithm for SRF Theory with Three Phase Shunt Active Power Filter

Shunt Active Power Filters (APFs) are the up-to-date solution to power quality problems. Harmonic reference detection is the key word for the proper operation of shunt APF. One of the most famous detection control schemes for shunt APFs is the Synchronous Reference Frame (SRF). In this paper, two new modifications of (SRF) detection control scheme are presented. The first modification is done by introducing a new scheme for the dc bus control loop. The second modification is accomplished by implementing the SRF without load current sensors and using only the supply current sensors. These improvements, compared to the conventional (SRF), simplify the control system, minimize the system delay time, improve the APF performance, and reduce the cost of the system. The simulation results, using MATLAB/SIMULINK, demonstrate the viability and simplicity of the modified control scheme, its success in meeting power quality standards limits, and increasing the accuracy of generated reference signal.

Bi-directional single-phase half-bridge rectifier for power quality compensation

A single-phase half-bridge rectifier with a capacitor clamped scheme is proposed. Four power switches and one flying capacitor are employed in the proposed rectifier. Bipolar and unipolar PWM control schemes are used to perform power factor correction and achieve low total harmonic distortion of line current. A neutral point voltage balance compensator, hysteresis current controller and DC link voltage regulator are used to balance neutral point voltage, to track line current command, and to maintain the constant DC bus voltage. The proposed control scheme and the circuit configuration can also perform a shunt active power filter operation to eliminate the harmonic currents and compensate the reactive power generated from the nonlinear load. Analytical and experimental results are presented to illustrate the validity and effectiveness of the proposed control scheme.