Harmonic Mitigation Methods Research Articles

Analysis of the Impact of Volt/VAR Control on Harmonics Content and Alternative Harmonic Mitigation Methods

Analysis of the Impact of Volt/VAR Control on Harmonics Content and Alternative Harmonic Mitigation Methods

Harmonic Mitigation using Hybrid Power Filter to Improve Power Quality

This paper represents a power quality improvement using harmonic mitigation method in distribution and transmission system. This include the hybrid power filter for mitigating the harmonic in the power system, the hybrid power filter is the combination active power filter ,passive power filter and voltage source inverter with the passive component like a capacitor and the inductor. The drawback of the active and the passive power filter is overcome by designing the hybrid power filter, the capability of harmonic mitigation can be increased with dc link voltage of the voltage source inverter. in this two method of implementation is adopted for harmonic mitigation in power system like hybrid mode and the passive mode , in passive mode the passive component is used in series such as capacitor and inductor and in hybrid mode the voltage source inverter is used along with the LC-filter . The power quality improvement and the reactive power control is also represented in this paper The analysis and MATLAB simulation give the proper solution to mitigate the harmonic in the distribution and the transmission system to improve the power quality and system stability . Index Terms— ,FFT Analysis hybrid power filters, passive power filters, power system harmonics, reactive power control., Total Harmonic Distortion, power quality, transmission and distribution network..

A System-Level Harmonic Control Method Based on Multibus Voltage Detected APF Without Exact Phase Synchronization

The decentralized distribution of nonlinear harmonic loads drives the trend of harmonic control from local compensation to system-level mitigation. Based on the active power filter (APF) with multi-bus harmonic detections, comprehensive control of harmonic distortions in multiple buses achieves, which is so-called system-level harmonic mitigation. However, existing system-level harmonic mitigation methods require high-speed data exchange for real-time phase synchronization among multiple buses, which reduces the feasibility of the methods. To reduce the burden of communication, a system-level harmonic mitigation method without inter-bus phase synchronization is proposed in this paper. Firstly, the phase synchronization problem is analyzed, and control system of multi-bus detected APF is proposed, in which the reference phase of each detector could be set locally. Then, a new online system-level harmonic mitigation model is introduced and solved to obtain the optimal APF current reference. Subsequently, the closed-loop control strategy of multi-bus detected APF is raised and four control stages are designed to cope with different situations. Finally, an eight-bus network with dynamic harmonic loads is designed in simulation and experiment. According to the results, multi-bus harmonic voltage distortions in the network could meet the standard. The proposed method contributes to achieving good harmonic compensation performance without multi-bus phase-synchronization.

Improved Control Method for Voltage Regulation and Harmonic Mitigation Using Dynamic Voltage Restorer

The increasing concerns of sensitive industrial customers and electrical utility corporationsregarding Power Quality (PQ) issues have driven the development of innovative solutions. This paperintroduces an enhanced control method based on Smooth Approximation Super Twisting Algorithm(SASTA) for the Dynamic Voltage Restorer (DVR) to achieve effective regulation of the critical load (CL)voltage to its nominal value while compensating for harmonics induced by the grid. The findings highlightthe significance of the improved control method in enhancing the DVR's performance for voltage regulationand harmonic distortion compensation. By implementing this control system, the DVR successfullymitigates deviations in voltage amplitude and reduces harmonic distortions in the CL voltage, therebyimproving power quality. To evaluate the performance of the proposed control method, extensivesimulations are conducted using the MATLAB/Simulink SimPower System toolbox. The resultsdemonstrate that the SAST-SMC for the DVR can accurately regulate the voltage in less than 2.3milliseconds (ms) and harmonics mitigation under 5% as per IEEE standards.

Harmonics Signal Feature Extraction Techniques: A Review

Harmonic estimation is essential for mitigating or suppressing harmonic distortions in power systems. The most important idea is that spectrum analysis, waveform estimation, harmonic source classification, source location, the determination of harmonic source contributions, data clustering, and filter-based harmonic elimination capacity are also considered. The feature extraction method is a fundamental component of the optimization that improves the effectiveness of the Harmonic Mitigation method. In this study, techniques to extract fundamental frequencies and harmonics in the frequency domain, the time domain, and the spatial domain include 67 literature reviews and an overall assessment. The combinations of signal processing with artificial intelligence (AI) techniques are also reviewed and evaluated in this study. The benefit of the feature extraction methods is that the analysis extracts the powerful basic information of the feedback signals from the sensors with the most redundancy, ensuring the highest efficiency for the next sampling process of algorithms. This study provides an overview of the fundamental frequency and harmonic extraction methods of recent years, an analysis, and a presentation of their advantages and limitations.

DE SHM Based Harmonic Minimization for Modified PUC 15 Level Inverter

A 15-level Modified Packed U-cell (MPUC) Inverter is investigated in this study, and a Selective Harmonic Mitigation (SHM) method is used to reduce and eliminate several harmonic components on the output voltage, resulting in a lower Total Harmonic Distortion (THD) factor. The proposed MPUC-15 inverter can provide a 15-level output with only eight switches, making it the most compact inverter to date. In order to achieve the 15-level output, the inverter's dc link voltage is kept in the ratio of 1/4:3/4:1. A detailed explanation of the PMUC15 inverter's operation with various switching states is provided. The MPUC15 inverter allows for the elimination of more harmonics. However, the equation of the harmonic becomes more complex as additional switching angles emerge in the harmonic equations, which are difficult to solve using typical linear optimization methods. The SHE-PWM equations for a 15-level inverter are created and solved using Deferential Evaluation (DE) with a variable modulation index, a current optimization method. The reported output THD has been less than 5%, and angles for various modulation indexes have been compiled and provided in tabular format. The inverter prototype is built in MATLAB®/Simulink, with a Typhoon HIL SCADA setup for testing the results of the DE algorithm.

Microgrid Harmonic Mitigation Strategy Based on the Optimal Allocation of Active Power and Harmonic Mitigation Capacities of Multi-Functional Grid-Connected Inverters

Harmonic pollution sources in microgrids have the characteristics of high penetration and decentralization, as well as forming a full network. Local harmonic mitigation is a traditional harmonic mitigation method, which has the disadvantages of complexity and costly operation. Based on the idea of the decentralized autonomy of power quality, this paper establishes a comprehensive optimization model of the active power and harmonic mitigation capacities of grid-connected inverters based on two-layer optimization and realizes harmonic mitigation. Firstly, based on the harmonic sensitivity analysis, the calculation method of harmonic mitigation capacity is given. Secondly, a two-layer model of harmonic mitigation optimization is established. The upper-layer optimization model takes the minimum operation cost of the microgrid as the objective and the active power reduction in the multi-functional grid-connected inverter (MFGCI) as the optimization variable. The lower-layer optimization model offers the best harmonic mitigation effect as the objective and the harmonic current compensation as the optimization variable. According to the relationship between the total remaining capacity of MFGCI and the capacity required for harmonic mitigation, there are three different objective functions in the lower-layer optimization model. Then, the model solving steps are provided. Finally, an example shows that the proposed optimization model can achieve harmonic mitigation at different times. Compared with the case without active power optimization, the operation cost of the whole system can be reduced by up to 14.6%, while ensuring the harmonic mitigation effect. The proposed method has the advantages of a harmonic mitigation effect and economical system operation.

Multi-Time Scale Harmonic Mitigation for High Proportion Electronic Grid

As new energies integrated into grid, the harmonics in the grid are more serious, and the Voltage Detection Active Power Filter (VDAPF) has been used as the mitigation equipment to solve the harmonic problems in power electronic distribution network. The global optimization method generally utilizes 15 min to mitigate harmonic which is named long-time-scale, and it is impossible to mitigate harmonic timely. This paper studies a multi-time-scale harmonic mitigation method which adds 5 min prediction to the global optimization method which is named multi-time-scale. The objective is to correct the deviation of harmonic caused by the long-time-scale harmonic prediction error. This paper utilizes MPC to predict the amplitude and phase variation of the harmonics in short time scale, and utilizes distributed VDAPF to optimize harmonic in long time scale. The IEEE 33 nodes system was used as an example to conduct a comparative analysis of mitigation effects in two different harmonic injection scenarios which injected separately 10 and 20%. The results shows that the mitigating effect of the global optimization method is limited under two different harmonic injection scenarios, and it needs to combine with short time scale harmonic prediction information to ensure the effectiveness and rationality of the mitigation results. When the harmonic current fluctuates, there are unqualified voltage distortion nodes in each region, and the voltage distortion rate is larger. But the MPC can change harmonic prediction in a short time, so every harmonic of each VDAPF conductance values is set bigger, and harmonic conductance of the higher harmonics is relatively lower.

Robust optimization based harmonic mitigation method in islanded microgrids

Power quality issues in islanded microgrids comprising of various renewable energy sources have recently gained more attention. As the harmonic mitigation capability from distributed energy resources will vary for different network topologies, this paper introduces a unified single-end harmonic mitigation approach using a robust optimization model. In the proposed method, a central controller receives voltage harmonic distortion measurements of all buses in the microgrid, optimizes the global information, and then sends back the optimal voltage harmonic components to the local controller of each distributed generation units, which is added to the voltage reference generated by the respective droop controllers locally. The robustness lies in the design of the objective function in the central controller to solve a multi-attribute optimization problem in minimizing both the average total harmonic distortion (THD) and THD of the critical bus in the microgrid considering different coefficients for each term. It has been proved with a set of numerical simulations with different parameters that the search space is reduced around the global minima, which considerably reduces the search time and the number of iterations. The results show that the suggested controller is robust and effective with respect to the different coefficients of the modified objective function to mitigate voltage harmonic distortion in islanded microgrids.

Improved Control Method for Voltage Regulation and Harmonic Mitigation Using Electric Spring

An electric spring (ES) with series connection to non-critical loads (NCLs) is mainly known as a smart load (SL) technology that can compensate undervoltages and overvoltages. In this paper, an improved control method is presented for the electric spring to regulate the effective value of the critical load (CL) voltage to the nominal value and to compensate the harmonics of the critical load voltage caused by the grid side. The electric spring’s performance for simultaneous voltage magnitude regulation and harmonic distortion compensation is investigated through simulation studies. The results are compared with those of a conventional control scheme. It has been demonstrated that the electric spring, using the improved control system, reduces the amplitude deviation and distortion of critical load voltage.

A Newly-Developed Control Method for Harmonic Mitigation in PV Grid-Connected Inverters Under Electric Arc Furnaces in Industrial Microgrids

A microgrid (MG) is a discrete energy system consisting of distributed generation (DG) and loads or nonlinear loads that is able to operate at the same time the main grid is operating. The DG units can operate in parallel with the main grid or in an MG mode. The unbalanced and nonlinear characteristics of numerous loads that are in connection with the power system have the potential to bring about some problems, in terms of power quality, which can affect other consumers. For instance, the electric arc furnaces (EAFs) cause considerable problems for power quality. The instantaneous power theory (pq) and the coordinate formulation (dq) are proposed in this paper for harmonic current compensation for PV grid-connected inverters and EAF in MGs. With the proposed control strategy under EAF conditions, the total harmonic distortions of the system current were decreased from 38.24% to 3.25%, which duly satisfies the IEEE 519-1992 standard.

Optimal Harmonic Mitigation in Distribution Systems with Inverter Based Distributed Generation

In recent years, with the widespread use of non-linear loads power electronic devices associated with the penetration of various renewable energy sources, the distribution system is highly affected by harmonic distortion caused by these sources. Moreover, the inverter-based distributed generation units (DGs) (e.g., photovoltaic (PV) and wind turbine) that are integrated into the distribution systems, are considered as significant harmonic sources of severe harmful effects on the system power quality. To solve these issues, this paper proposes a harmonic mitigation method for improving the power quality problems in distribution systems. Specifically, the proposed optimal planning of the single tuned harmonic filters (STFs) in the presence of inverter-based DGs is developed by the recent Water Cycle Algorithm (WCA). The objectives of this planning problem aim to minimize the total harmonic distortion (THD), power loss, filter investment cost, and improvement of voltage profile considering different constraints to meet the IEEE 519 standard. Further, the impact of the inverter-based DGs on the system harmonics is studied. Two cases are considered to find the effect of the DGs harmonic spectrum on the system distortion and filter planning. The proposed method is tested on the IEEE 69-bus distribution system. The effectiveness of the proposed planning model is demonstrated where significant reductions in the harmonic distortion are accomplished.

Review of Harmonic Mitigation Methods in Microgrid: From a Hierarchical Control Perspective

The microgrid concept has been emerged into the power system to provide reliable, renewable, and cheaper electricity for the rising global demand. When the microgrids are introduced, there will be several concerns, such as active and reactive powers' sharing, load management, connecting to the main grid, and voltage and current deviations. Recently, with the fast deployment of distributed generation, methods to mitigate microgrid harmonics caused by nonlinear loads and power electronic devices have become one of the main focus areas. Consequently, many research works are devoted to this area, introducing different harmonic mitigation methods suitable for the microgrids. Hence, the main goal of this article is to clearly present a comprehensive review of harmonic mitigation methods from a hierarchical control viewpoint. The control strategies proposed to mitigate harmonics are classified into three groups: primary, secondary, and tertiary. Furthermore, this overview draws a sketch on the global trends in harmonic mitigation methods of an ac microgrid directly applicable to today's smart grid applications.

An improved method for harmonic mitigation and stability improvement of the grid-connected inverters under local load variation and weak grid condition

Variable voltage and current harmonics appear to be critical challenges for grid-connected inverters at the point of common coupling (PCC). The nonlinear local load and grid impedance variations contribute a lot to the problem. In this paper, a novel control strategy is proposed using the variable virtual admittance (VVA) and series active filter concepts capable of improving harmonic mitigation and stability in grid-connected inverters. The magnitude and phase angle of the VVA are adaptively determined according to the local load variation. Moreover, the series active filter injects a series voltage to reduce the grid impedance effect. The proposed control method can be simply implemented, where sinusoidal grid-injected current and sinusoidal local load voltage can also be achieved under local load variation and weak grid condition. The theoretical approach is verified using several simulation case studies in Matlab/Simulink software.

Experimental Validation of a Novel Method for Harmonic Mitigation for a Three-Phase Five-Level Cascaded H-Bridges Inverter

In modern high-power electrical drives, the efficiency of the system is a crucial constraint. Moreover, the efficiency of power converters plays a fundamental role in modern applications requiring also a limited weight, such as the electric vehicles and novel more electric aircraft. The reduction of losses pushes for systems with a dc bus and a high number of dc/ac converters, widespread in the vehicle, not burdened by a too expensive data processing system. The purpose of this article is to concur to reduce losses by proposing an innovative selective harmonic mitigation method based on the identification of the working areas where the reference harmonics present lower amplitudes. In particular, the main objective is to find a new way to calculate the control angles in real-time operation without solving nonlinear equations, whose resolution would require expensive controllers. Through a very simple approach, the polynomial equations, which drive the control angles, were detected for a three-phase five-level cascaded H-bridge inverter and implemented in a digital system to real-time operation with a low computational cost. As a result, a comparison between the simulation and experimental behavior is presented. In the last part of this article, a real electric machine is driven by considering the appropriate working areas and current harmonics are also evaluated.

Performance Evaluation of 3-Phase Series Active Filter in a Grid Tied PV-System employing Sinusoidal Current Control Strategy

The basic aim of the electric power sector is to produce power as when required at the suitable sites, then transmitting and distributing to various load centres or consumers, retaining the quality (sustaining frequency and voltage at stated value) and fidelity of supply at an economical tariff. The primary purpose is to have a brief idea about various power quality advancement techniques and to learn the prospects of various harmonic mitigation methods with a focus on Sinusoidal current control strategy (SCCS). The SCCS is a time domain control strategy established on instantaneous p-q theory. The control strategy has been elaborated here in details and has been implemented using MATLAB 2016A. The results have been given and described in details explaining efficacy of the above control strategy. Since sinusoidal current control strategy is a simple and effective control strategy it has tremendous potential for application in the Distributed Generation oriented system. Further researches can be extended toward application machine learning techniques for the improvisation of control performance of the active power filters.

Passive filters' placement considering parameters' variations

The presence of power system harmonics due to the increasing number of nonlinear loads in modern industry has become a growing concern for the engineers. Among the harmonic mitigation methods available, the use of single tuned passive filters is 1 of the techniques most widely employed due to their simplicity and low cost. The formulation here presented considers the probabilistic nature of parameters' deviations of the filters and of the system by using the Monte Carlo statistical simulation method. The optimization determines a set of single tuned harmonic filters to obtain the maximum saving of annual cost as well as the best power quality indices of the circuit. The obtained solutions comply with the constraints of power quality and of stress of capacitors. The multiobjective optimization problem is solved by the nondominated sorting genetic algorithm. The presented methodology is tested with an example circuit of literature.

Resonance damping in array cable systems by wind turbine active filtering in large offshore wind power plants

The application of active filtering in large offshore wind power plants (WPPs) is presented in this study. The harmonic challenges such as sources of harmonic emission and resonances are identified and briefly explained. Also modern remedial harmonic mitigation methods as of active filtering are described and their application in real-life WPP systems demonstrated. It is underlined that WPP components such as widespread medium-voltage cable system and offshore grid transformers can introduce significant low-frequency parallel resonances which can cause a significant harmonic voltage distortion at the point of common coupling. Active filtering in modern grid-side converters used in wind turbines is applied simultaneously keeping sufficient harmonic/noise rejection. Extensive harmonic stability studies are also shown to prove the overall system robustness.

Inter-harmonics in multi-terminal VSC-based HVDC systems

Multi-terminal voltage sourced converter (VSC)-based high voltage direct current (HVDC) system composes of a number of VSCs connected to an HVDC grid (or dc grid). The dc grid is often configured by cable interconnections between converter stations, thus imposing resonance issues affecting harmonic interaction in the system. Based on the harmonic transfer characteristics of VSC and HVDC systems, the appearance and the interaction of inter-harmonics in the multi-terminal VSC-based HVDC system are analyzed. Simulation models are built and implemented using SimPowerSystems in MATLAB. The simulation results show that, a series of inter-harmonics are produced and tend to be dominant in low-frequency range. Especially in the dc grid, the inter-harmonic transfer can be magnified due to inter-harmonic resonances. The complex resonance issues in the dc grid are investigated in combination with interaction through the VSC, it is beneficial to harmonic filter designs as well as other harmonic mitigation methods.

Analysis and Mitigation of Resonance Propagation in Grid-Connected and Islanding Microgrids

The application of underground cables and shunt capacitor banks may introduce power distribution system resonances. In this paper, the impacts of voltage-controlled and current-controlled distributed generation (DG) units to microgrid resonance propagation are compared. It can be seen that a conventional voltage-controlled DG unit with an LC filter has a short-circuit feature at the selected harmonic frequencies, while a current-controlled DG unit presents an open-circuit characteristic. Due to different behaviors at harmonic frequencies, specific harmonic mitigation methods shall be developed for current-controlled and voltage-controlled DG units, respectively. This paper also focuses on developing a voltage-controlled DG unit-based active harmonic damping method for grid-connected and islanding microgrid systems. An improved virtual impedance control method with a virtual damping resistor and a nonlinear virtual capacitor is proposed. The nonlinear virtual capacitor is used to compensate the harmonic voltage drop on the grid-side inductor of a DG unit LCL filter. The virtual resistor is mainly responsible for microgrid resonance damping. The effectiveness of the proposed damping method is examined using both a single DG unit and multiple parallel DG units.