Shunt Active Power Filter System Research Articles

TLBO trained an ANN-based DG integrated Shunt Active Power Filter to Improve Power Quality

In terms of power quality, the rising number of nonlinear loads in modern use has caused warning signs for power system and power engineering professionals. Every day, utilities have to deal with harmonic distortion caused by a growing number of non-linear power electronic equipment. To keep the system's power supply in good condition, a shunt active filter is used to filter out unwanted harmonics in the signal. This study presents a practical and low-cost method for reducing harmonics and enhancing distribution network power quality by means of the use of PV-integrated Shunt Active Power Filters (SAPF). With a teaching-learning-based optimized artificial neural network controller (TLBO-ANN) and the required DC power is extracted from the PV module. SAPF's TLBO-ANN algorithms are intended to increase system performance by reducing total harmonic distortion (THD). Here, the research work was performed in three stages to mitigate grid current harmonics. The first-stage SAPF system comprises a three-prong voltage source converter and uses DC power derived from photovoltaic panels. The P&O algorithm is used to get the maximum power out of a photovoltaic array. In the second stage, the BBO algorithm is used to fine-tune a conventional PI controller, resulting in values for and that increase the controller's performance. Furthermore, it is intended to use the BBO-PI controller's input and output values as training data for the ANN controller. This ANN controller is currently being tuned with the TLBO algorithm to find optimal values for the weight and bias parameters. In the third stage, the converter in PV-SAPF will inject the active power required by the load by using active current control theory, which means the inverter of SAPF is working like DG as well as the active power filter. Employing MATLAB simulations, we concluded that the proposed method is extremely adaptable and highly efficient in lowering harmonic currents that are brought on by non-linear loads.

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.

An optimized proportional resonant current controller based genetic algorithm for enhancing shunt active power filter performance

Current harmonics produced by nonlinear loads have destructive effects that affect the power quality of the power system and cause serious problems throughout the network. Active Power Filter (APF) is one of the best and most common solutions to reduce or eliminate harmonic disturbances; But due to the complexity and sensitivity of these filters, the accurate and fast performance of the control technologies used in it is the important and basic requirement. Therefore, by performing accurate and optimal adjustments for APF control, system performance and power quality level can be improved significantly. In this article, the design principles of Shunt Active Power Filter (SAPF) are introduced and the optimal control method of this system is explained by providing appropriate modeling. Also, as a suitable structure for the current control of the SAPF system, a Proportional-Resonant (PR) controller optimized by Genetic Algorithm (GA) is proposed. The PR controller with the capability of accurate tracking of harmonic currents and fast dynamic response is highly compatible with the SAPF system. In general, the goal is to achieve better and more appropriate performance to reduce harmonic disturbances and create a robust, faster, more accurate, flexible, stable, and optimal performance of these systems in detecting and generating compensation signals. The simulations have been done in MATLAB/SIMULINK, and also the experimental tests of this device have been done and validated in a real DSP-based SAPF. Finally, according to the results obtained under steady-state conditions with a favorable dynamic response, the Total Harmonic Distortion (THD) of the grid current has been significantly reduced from 20.2 % to 4.2 % for the R-L load and from 56.1 % to 4.5 % for the R-C load with a power factor of almost unity. These results confirm the optimal and standard performance of the proposed method.

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.

Harmonic oscillation analysis and stabilization method comparison of shunt active power filter in full compensation mode

AbstractThe harmonic compensation of SAPF (shunt active power filter) may trigger harmonic oscillation due to the interaction with grid impedance and non‐linear loads, which distorts the power quality. In previous research, the relevant mechanism has been studied. However, the SAPF generally employs complex harmonic detection algorithm, which significantly increases the computational demands. The SAPF in full compensation mode can effectively solve this problem. But the modification of harmonic detection link may change the oscillation mechanism and previous stabilization methods need to be re‐evaluated. Therefore, this paper establishes the small signal model of the SAPF system in full compensation mode and investigates its oscillation mechanism. It is revealed that harmonic compensation and passive resonance collectively induce the harmonic oscillation. Based on the model, the working mechanism and application performance of the main stabilization methods proposed in the past (harmonic virtual admittance and harmonic compensation canceling) are analyzed and compared. However, neither of them can achieve effective stabilization without sacrificing the performance of compensation. Consequently, the harmonic phase compensation method is proposed to achieve the stabilization of the SAPF system in full compensation mode without affecting normal compensation. Finally, simulations and experiments are performed to verify the mechanism analysis and proposed methods.

Noninteger Lexicographic-Optimization-Based Sequential Model-Predictive Fault-Tolerant Control of T-Type Shunt Active Power Filter

Fault-tolerant control (FTC) strategies have been proposed to improve the reliability of power electronic systems. However, the FTC of the three-level T-type converter based shunt active power filter (SAPF) remains limited by redundant devices. To address this problem, an FTC strategy called sequential model predictive tolerant control (SMPTC) is combined with a nonintegral lexicographic optimization (LO) algorithm for solving multiobjective optimization problems. First, the power circuit, space voltage vector diagram, harmonic extraction, and prediction models of the SAPF system are introduced. Second, based on power-switch fault analysis, an adaptive dc bus voltage regulation method is proposed, which ensures that the candidate voltage vectors are fully utilized in the fault state. Third, an LO-SMPTC strategy is proposed by designing a sequential predictive controller that considers the neutral point (NP) voltage and the tracking of the SAPF output current. Compared with the traditional model predictive control, the proposed method not only achieves NP voltage balance and excellent harmonic compensation but also eliminates the selection of weighting factors, thereby improving the control flexibility and time efficiency. Finally, the effectiveness of the LO-SMPTC on the dc bus voltage, NP voltage oscillations, grid current power quality, and pole voltage under different scenarios is demonstrated through experiments.

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.

Optimal Cascade Non-Integer Controller for Shunt Active Power Filter: Real-Time Implementation

Active power filters (APFs) are used to mitigate the harmonics generated by nonlinear loads in distribution networks. Therefore, due to the increase of nonlinear loads in power systems, it is necessary to reduce current harmonics. One typical method is utilizing Shunt Active Power Filters (SAPFs). This paper proposes an outstanding controller to improve the performance of the three-phase 25-kVA SAPF. This controller can reduce the current total harmonic distortion (THD), and is called fractional order PI-fractional order PD (FOPI-FOPD) cascade controller. In this study, another qualified controller was applied, called multistage fractional order PID controller, to show the superiority of the FOPI-FOPD cascade controller to the multistage FOPID controller. Both controllers were designed based on a non-dominated sorting genetic algorithm (NSGA-II). The obtained results demonstrate that the steady-state response and transient characteristics achieved by the FO (PI + PD) cascade controller are superior to the ones obtained by the multistage FOPID controller. The proposed controller was able to significantly reduce the source current THD to less than 2%, which is about a 52% reduction compared to the previous work in the introduction. Finally, the studied SAPF system with the proposed cascade controller was developed in the hardware-In-the Loop (HiL) simulation for real-time examinations.

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.

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.

Simulation and Analysis of a Three-phase Shunt Active Power Filter

This paper presents the simulation-based study and results of a three-phase shunt active power filter (SAPF) for power quality improvement. The power quality of the power systems is degraded because of the presence of non-linear loads at the consumer end. The SAPF can reduce the impact of harmonics caused by the non-linear loads. The analyzed SAPF system is modeled and simulated using MATLAB-Simulink workspace. The ultimate goal of this study is to improve the total harmonic distortion of the system as per the standards defined by IEEE-519.

Design and implementation of ANN-based SAPF approach for current harmonics mitigation in industrial power systems

This article describes with Shunt Active Power Filter (SAPF) for compensation of reactive Power (P), current harmonics. An ADALINE based neural network current estimator can control the SAPF to maintain sinusoidal source currents and unity Power Factor (PF). The three-phase (III-Phase) load currents are sensed and measured by Least Mean Square(LMS) algorithm based on ADALINE, the weights obtained with the help of online calculation, and then these weights are multiplied with the help of unit vector, which gives the fundamental frequency of Load Currents (LC). The DC link voltage (V) of the V Source Converter, maintained at a constant value, and it can work as the SAPF, and various simulation results are presented under the steady-state conditions using the PI controller. The switching action of VSC is performed using Hysteresis Current Control based on pulse width modulation, which makes the source currents should follow the reference source currents. The MATLAB based simulation results and implementation results are obtained to determine the efficacy of the SAPF with ADALINE based neural network control for load compensation. SAPF system meets IEEE Standard 519 recommended harmonic standards for different rated nonlinear loads under balanced supply conditions.

Robust control method for LCL‐type shunt active power filter under weak grid condition

This study presents an improved double closed-loop current (fundamental and harmonics current) control method for inductive-capacitive-inductive (LCL) type shunt active power filter (SAPF), which is designed to enhance the robustness of the SAPF system to adapt weak grid application condition. Due to the variation of weak grid impedance, fundamental current control loop based on grid current feedback control method may become unstable, a robust parameters design method in discrete z-domain according to amplitude-frequency and phase-frequency characteristics is proposed to fit the grid impedance variation. The harmonics current of non-linear load exists in a wide frequency range, normal resonant controller will cause the system unstable due to the negative −180° cross of phase at high-frequency range, a digital phase-lead resonant controller (PL-RC) is proposed to extend the bandwidth of the harmonics current control, then the quantities of the PL-RCs used to suppress harmonics can be increased considerably compared with normal resonant controller. Experimental results are presented to verify the effectiveness of the robust parameters design method and the proposed PL-RC.

Admittance Modeling, Analysis, and Reshaping of Harmonic Control Loop for Multiparalleled SAPFs System

Large-scale harmonic current pollution exists widely in power grid due to the massive applications of power electronic equipment, which affects the efficiency and reliable operation of the whole system. Owing to its excellent controllability, dynamic response performance, and compensation precision, the multiparalleled shunt active power filters (SAPFs) is widely used in the past few decades. However, under the weak grid condition, a coupling relationship between multiple grid-connected inverters is formed through PCC because of the non-negligible grid impedance, which will cause the harmonic instability problem. Compared with the application fields of renewable energy generation and energy storage, the stability analysis for multiparalleled SAPFs system not only needs to consider the current loop, but also the harmonic control loop and harmonic load comprehensively, which increases the complexity of stability analysis and control. In this article, taking harmonic suppression as the application background, the global-admittance-based stability analysis method for multiparalleled grid-connected inverters system under the non-negligible grid impedance condition is proposed. Through admittance reshaping, the active damping method for suppressing system instability is given. Besides, the description and cause analysis for common instability cases are also presented. The simulation and experimental results verify the effectiveness of the proposed method.

Improved instantaneous power theory based current harmonic extraction for unbalanced electrical grid conditions

This paper presents a novel harmonic extraction method named as “virtual input signal based instantaneous power theory (VIS-IPT)”. In this study, VIS-IPT is tested in a shunt active power filter (SAPF) for improving the performance under unbalanced electrical energy quality issues. In the operational process, VIS-IPT is used to generate the compensation signals consisting of harmonic/reactive currents. In the proposed method, reference signal generation is extracted for each phase, separately. In VIS-IPT, the compensation signals are obtained from the calculated powers through multiple-phase inverse Clark transformation. In this way, it eliminates the drawback of conventional IPT which calculates the undesired average reference under unbalanced situations. Moreover, the additional use of PLL for synchronization is eliminated in the proposed method. In this context, a three-phase SAPF system with nonlinear load groups is constructed and analysed in Matlab/Simulink environment in order to prove the efficacy of the proposed method. In addition, the proposed VIS-IPT method is compared with the conventional IPT method through a variety of case studies. The proposed method is examined under different case studies including balanced/unbalanced/distorted voltage and balanced/unbalanced load conditions. The case studies show that the proposed method has excellent compensation capability performance in comparison with the conventional method.

Modified Modeling and System Stabilization of Shunt Active Power Filter Compensating Loads with μF Capacitance

The interactions between shunt active power filter (APF) and capacitance load tend to result in stability problems and resonance. The conventional model of a shunt APF is not precise enough to reflect this phenomenon. To address it, this paper proposes a modified shunt APF system model to accurately reflect various stability problems. This paper also studies the mechanism of positive feedback resonance brought by capacitance load and proposes a modified hybrid controller to improve the stable margin of the system, making the shunt APF work stably under different working conditions where there are μF capacitors on the demand side. The correctness and validity of the proposed strategy are verified by simulation analysis and prototype experiments.

A multi-modular shunt active power filter system and its novel fault-tolerant strategy based on split-phase control and real-time bus communication

We first present a new multi-modular shunt active power filter system suitable for large-capacity compensation. Each module in the system has the same circuit topology, system functionality, and controller design, to achieve coordination control among the modules. The module’s reference signals are obtained by multiplying the total reference signal by the respective distribution coefficient. Next, a novel fault-tolerant approach is proposed based on split-phase control in the a-b-c frame and real-time bus communication. When a phase fault occurs, instead of halting the whole module, the proposed strategy isolates only the faulted bridge arm, and then recalculates the distribution coefficients and transfers the compensation capacity to the same phases of the other normal modules, resulting in a continuous operation of the faulted module and optimization of the remaining usable power devices. Through steady-state analysis of the post-fault circuit, the system stability and control reliability are proven to be high enough to guarantee its engineering application value. Finally, a prototype is established and experimental results show the validity and feasibility of the proposed multi-modular system and its fault-tolerant control strategy.

A Novel Hybrid Modular Three-Level Shunt Active Power Filter

Shunt active power filters (SAPF) are employed to improve power quality by injecting compensating harmonic current. The modular SAPF offers many new capabilities that are otherwise unavailable by the conventional SAPF, such as high crest factor compensating current and fast dynamic response. However, there are still challenges that are needed to be addressed, such as resonance and stability issues associated with the modular SAPF. To investigate these issues, this paper first presents a mathematical model for conventional modular SAPF system. Based on the mathematical analysis, a new hybrid three-level modular SAPF is presented that is composed of two types of modules, each with different current carrying capacities, LCL filter parameters, and switching frequencies. The proposed hybrid system provides a wider current tracking bandwidth and fast dynamic response as compared to the present modular SAPF. A novel self-adaptive active damping strategy is proposed that effectively suppresses resonance and coupling between modules. Mathematical analysis and experimental results have been used to verify the proposed system.

Study on the design and switching dynamics of hysteresis current controlled four‐leg voltage source inverter for load compensation

In a variable switching frequency control scheme, it is challenging to design the voltage source inverter (VSI) parameters without knowing the maximum and minimum switching frequencies. The switching frequency variation depends on the system parameters. Therefore, the expression for frequency variation in one inverter topology does not hold in other topologies. The design of hysteresis current controlled four-leg shunt active power filter (APF) requires the switching dynamics analysis to ensure satisfactory performance of the inverter. In this study, a detailed analysis on the switching dynamics of hysteresis current controlled four-leg VSI and design of various inverter components for compensating unbalanced and non-linear loads are presented. The results obtained from these analyses can be used in any applications involving hysteresis current controlled four-leg VSI. These results are supported by detailed simulation studies conducted on a three-phase four-leg shunt APF system using Matlab/Simulink. The theoretical studies and design of passive components are also verified by conducting experiments on a prototype of four-leg shunt APF developed in the laboratory.

A comparative analysis of DFPI correctors and different techniques to regulate a shunt active power filter

Power quality is a subject of intense study over recent years, given that it affects the economic impact and costs of utilities, supply and manufacturing. Modern powered electronic equipment is usually nonlinear in nature and causes propagation of harmonic current. This disruptive current can be countered by various solutions, but active power filtering is the most captivating solution. In this paper, a Shunt Active Power Filter (SAPF) system is considered with a new corrector design for both the DC and AC sides. The new design is based on an association between double fuzzy logic and single PI correctors resulting in two 'DFPI' correctors devoted to regulating the DC voltage and the AC current of the SAPF. The DFPI corrector is more advantageous than the classic PI or fuzzy controllers implemented alone for regulation purposes of the SAPF control variables (DC voltage and the AC current). This is demonstrated, in this paper, through the addressed theoretical analysis of the proposed DFPI corrector and the studies shown in the simulation section comparing the proposed DFPI, single fuzzy, double fuzzy and PI controllers. Performances in terms of the filtering quality of the AC feeder side and the SAPF DC-bus voltage regulation quality (THDis%/THDVs%) are noted. The obtained numerical results prove the effectiveness of the DFPI corrector which also described a faster response time, a reduced overshoot and a lessened static error.