Harmonic Limits Research Articles

Evaluation of Photovoltaic Inverters According to Output Current Distortion in a Steady-State and Maximum Power Point Tracking

The limits of direct current (DC) injection and output current distortion of grid-connected photovoltaic (PV) inverters are specified in the IEEE 1547-2018 standard. The standard prescribes limits of output current harmonics, but the input voltage and power at which output current distortion is measured are not specified. This manuscript presents the results of DC injection and output current distortion measurements for three commercial single-phase PV inverters, with 3 kVA, 3.3 kVA, and 6 kVA rated power. During the measurements, the inverters are powered by a programmable DC source that emulates the power voltage characteristic of a PV array, providing different input conditions. In addition to steady-state measurements at constant input voltage and power, the change in the output current spectrum over time during the maximum power point tracking (MPPT) is also measured. The results show that the output current distortion depends on the input voltage and power. Moreover, the current distortion of some of the tested inverters exceeds the limits specified by the standard in some cases. The presented results suggest that further research on the dependence of the output current distortion from PV inverters on their input power and voltage is needed.

ADALINE-based synchronous detection for enhanced shunt APF performance

Power quality issues caused by current harmonics from nonlinear and unbalanced loads are a growing concern. This paper presents a novel control strategy for four-wire shunt active power filters (SAPF) that surpasses existing conventional methods in mitigating harmonics and power factor correction. The strategy employs an improved synchronous detection method (SDM) enhanced by an adaptive linear neural network (ADALINE) trained using the least mean square (LMS) algorithm. This approach accurately estimates harmonic frequencies, enabling the SAPF to generate precise compensation currents. The effectiveness of the proposed method is validated through MATLAB-Simulink simulations under balanced supply conditions, encompassing diverse load scenarios. These simulation results are compared with those obtained using instantaneous power theory (IPT). They demonstrate the ability of the proposed method to achieve excellent harmonic identification and elimination, to comply with IEEE 519 harmonic limits, to ensure sinusoidal and balanced line currents, and to compensate for reactive power and neutral current. Furthermore, its simple architecture and noise robustness make it a promising solution for enhancing power quality.

Load Limiting Control for Component Life Extension

This paper presents the development of a novel life-extending control scheme for critical helicopter components subjected to significant fatigue loading. The primary objective is to synthesize a more efficient and less conservative life-extending control scheme than those currently available in the literature. The proposed load limiting control (LLC) scheme is a viable solution that addresses several issues that current life-extending control schemes suffer from, such as the neglect of fatigue damage induced by the harmonic component of loads and the inability to distinguish between aggressive and nonaggressive maneuvers. The proposed LLC scheme treats desired harmonic load limits as limit boundaries and recasts the problem of load limiting as a vehicle limit by computing a control margin (CM) using a limit detection and avoidance module. The computed CM is used as a cue to the pilot. The limit detection and avoidance module comprises an optimization algorithm, a model predictive controller, and a computationally simple onboard dynamical model. Simulations were conducted to demonstrate the effectiveness of the LLC scheme in limiting harmonic pitch link loads during flight. One significant outcome is that, with sufficient training, the pilot can skillfully track the cue within 0.5 s of initiating the tracking task.

A Simple Online Tuning Flux Weighting Factor in Finite Control Set – Predictive Torque Control for Induction Motor Drive

The Finite Control Set-Predictive Torque Control (FSC-PTC) is a practical and intuitive method to control an Induction Motor (IM). However, the challenge of this technique is the difficulty of tuning the weighting factor so that it performs optimally at all speeds. Hence, this paper proposes a new method for improving the optimization technique by automatically tuning the weighting factor using a flux controller. The flux controller is represented as a DC gain and designed to be proportional to the absolute value of the predicted stator flux error. This method eliminates the need for complex computation to select the suitable weighting factor while also efficiently regulating flux and torque. The proposed method is experimentally validated on a DS1104 controller board and compared to a constant flux weighting factor method that was tested under speed conditions. The results demonstrate that the new method can further decrease the torque ripple compared to the constant weighting factor while maintaining the flux ripple and harmonic distortion limits.

Experimental Validation of a Modular All-Electric Power Take-Off Topology for Wave Energy Converter Enabling Marine Renewable Energy Interconnection

Power electronic converters are an enabling technology for the emerging marine energy applications, such as using ocean waves to produce electricity. This paper outlines the power take-off system and its key components used in a wave energy converter offering modularity and scalability to generate power efficiently. The proposed power take-off system was implemented based on a modular multilevel converter and could be deployed to convert any alternating current electrical energy to a different alternating current for interconnection to grid or non-grid applications. Examples of widespread deployment are supplying electricity to coastal communities or producing clean drinking water. The analysis using both the simulation tests and laboratory experiments verified the design objectives and basic functionality of the developed power take-off system. An acceptable response using a field programmable gate array-based controlled laboratory testbench was achieved, complying with guidelines specified in the prevalent industry standards. Seamless operation during steady-state and transients for the studied wave energy converter was achieved as supported by the obtained results. The key findings of this work were experimentally examined under different load conditions, direct current bus voltage fluctuations, and generator speed–torque regulation. The ability of the power take-off system to generate high-power quality of the waveforms, e.g., against adhering to the IEEE 519-2022 standard for total harmonic distortion limits, is also confirmed.

Implementation of Shunt Active Power Filter Using DSP Controller Based on Synchronous Reference Frame for Harmonic Mitigation

This research paper introduces the concept of a shunt active power filter (SAPF) that leverages synchronous-reference-frame (SRF) theory to mitigate harmonics in the power system. The SAPF works by injecting a compensating current at the point of common coupling (PCC) to counteract the harmonics in the line and restore sinusoidal current waveforms. It employs a three-phase current-controlled voltage source inverter (VSI) with a DC link capacitor for active filtering. An SRF algorithm is designed for a low-voltage laboratory prototype utilizing the TMS320F28335 Digital Signal Processor (DSP). The experimental findings affirm that the control strategy effectively aligns with the recommended harmonic standard limits of IEEE 519-1992.

Design Enhancement of Grid-Connected Residential PV Systems to Meet the Saudi Electricity Regulations

Distributed grid-connected photovoltaic (PV) generation explores several methods that produce energy at or near the point of consumption, with the aim of reducing electricity losses among transmission networks. Consequently, home on-grid PV applications have garnered increased interest from both scientific researchers and industry professionals over the last decade. Nevertheless, the growing installation of intermittent nature residential PV systems (R-PV) in low-voltage distribution networks is leading to more cautious considerations of technology limitations and PV design challenges. This conservative perspective arises from the standpoint of grid quality and security, ultimately resulting in the revocation of PV connection authorization. Hence, the design of R-PV systems should consider not only the specifications of the PV panels and load profiles but also the characteristics and requirements of the connected power grid. This project therefore seeks to enhance the design considerations of grid-connected PV systems, in order to help the end-users meet the grid codes set out by the Saudi Electricity Regulatory Authority (SERA). Since the maximum amount of generated power is essential for PV system optimization, the ratio of grid strength to maximum transmitted power was employed to ascertain the suitable capacity of the PV system, while the assessment of PV power output was utilized to specify the system size. Furthermore, a battery energy storage system (BESS) with a small size (~10% of the PV capacity) is employed to enhance the PV power quality for a dependable grid interconnection. The BESS is equipped with a versatile power controller in order to achieve the designed objectives. The obtained results show an essential advancement in terms of power quality and reliability at the customer’s connection point. Moreover, with the design assessment process, the low-voltage ride-through (LVRT) and power factor requirements can be met, in addition to the total harmonic distortion (THD) and frequency transient limitations. The proposed solution assists end-users in efficiently designing their own R-PV systems while ensuring quality and sustainability for authorized grid interconnection.

Optimal sizing and siting of single tunned passive filter based on jellyfish algorithm

<p class="MsoNormal" style="margin-top: 10pt; text-align: justify;"><span lang="EN-US" style="font-family: 'times new roman', times, serif; font-size: 14pt;">The presence of electrical harmonics in low voltage networks causes many problems for customers, the most important of which is the decrease in the power quality beyond the permissible limits, which leads to a decrease in voltage for long periods, a decrease in power factor and a large losses in the electrical network due to the deformation of the electric waveform of voltage and current. The aim of this paper is to design an optimal passive filter and its optimal location to suppress the harmonic distortion in the distribution system that results from nonlinear loads. This filter will use single objective functions and multi objective functions that will minimize the proposed filter cost, the real power losses, total harmonic distortion "THD" and individual harmonic distortion "IHD". This will be done under the equality constraint of power balance and some inequality constraints such as filter parameters limits, quality factor limits, voltage limits, harmonic distortion limits. The optimal passive filter parameters and location will be calculated using the modern optimization techniques such jellyfish optimization technique. IEEE 33 bus radial system will be used for demonstrating results obtained by the proposed method.</span></p>

Optimal design of single-tuned filters for industrial power systems to reduce harmonic distortion using forest algorithm

ABSTRACT This paper presents a novel optimization algorithm for designing single-tuned filters in industrial power systems to reduce harmonic distortion. Single-tuned filters are cost-efficient, simple, and easy to maintain. We formulate the filter design as an optimization problem, minimizing costs while incorporating harmonic limits and system constraints. Our solution algorithm simulates tree growth, proliferation, and death based on the forest algorithm to generate optimal solutions. This enables both local and global searches for fast convergence and feasible designs. Unlike traditional approaches, we account for variations in filter components and system parameters caused by factors like manufacturing tolerances, operating temperature, and frequency variations. Our study contributes by designing adaptive filters that match practical systems. We validate our method against previous publications and other techniques like simulated annealing and teaching-learning-based optimization. Simulation results demonstrate the effectiveness of our approach in minimizing costs, satisfying operation constraints, and accounting for component variations in this complex problem.

Oppositional based artificial rabbits optimization applied for optimal allocation of nonlinear DG in distribution networks considering total harmonic distortion limit

This paper proposes a new optimization approach to identify the optimal placement and sizes of distributed generation (DG) units in a radial distribution network (RDN). Inverter-based DG also known as nonlinear DG (NLDG) units inject nonlinear current into the system, which can cause harmonic distortion. This harmonic distortion can limit the penetration of DG in the system by affecting the stability and reliability of the power system. Therefore, it is essential to consider harmonic distortion when identifying the optimal placement and sizes of DG units in RDNs to ensure DG’s safe and effective integration into the power system. The aim of the proposed work is to minimize real power loss, voltage deviation (VD), and total harmonic distortion limit (THD), and improve the voltage stability index (VSI) by integrating the search strategies of opposition-based learning and artificial rabbits optimization (ARO) to achieve better performance. The proposed algorithm, called opposition-based artificial rabbits optimization (OARO), considers different types of DG units like DG TYPE I and DG TYPE III and is suggested for two familiar RDNs: IEEE 33-bus, and 118-bus systems. The Pareto optimality concept has been introduced to solve the multi-objective problems of the systems. The simulation outcomes have been analyzed by comparing several optimization techniques in various cases. OARO has been shown to produce high-quality results with minimal iterations, reducing the time needed to solve the issue and conserving energy. Overall, the proposed approach offers a promising solution for identifying DG units’ optimal placement and sizes in RDNs while considering various operating scenarios.

A 2.4 GHz Wide-Range CMOS Current-Mode Class-D PA with HD2 Suppression for Internet of Things Applications.

Short-range Internet of Things (IoT) sensor nodes operating at 2.4 GHz must provide ubiquitous wireless sensor networks (WSNs) with energy-efficient, wide-range output power (POUT). They must also be fully integrated on a single chip for wireless body area networks (WBANs) and wireless personal area networks (WPANs) using low-power Bluetooth (BLE) and Zigbee standards. The proposed fully integrated transmitter (TX) utilizes a digitally controllable current-mode class-D (CMCD) power amplifier (PA) with a second harmonic distortion (HD2) suppression to reduce VCO pulling in an integrated system while meeting harmonic limit regulations. The CMCD PA is divided into 7-bit slices that can be reconfigured between differential and single-ended topologies. Duty cycle distortion compensation is performed for HD2 suppression, and an HD2 rejection filter and a modified C-L-C low-pass filter (LPF) reduce HD2 further. Implemented in a 28 nm CMOS process, the TX achieves a wide POUT range of from 12.1 to -31 dBm and provides a maximum efficiency of 39.8% while consuming 41.1 mW at 12.1 dBm POUT. The calibrated HD2 level is -82.2 dBc at 9.93 dBm POUT, resulting in a transmitter figure of merit (TX_FoM) of -97.52 dB. Higher-order harmonic levels remain below -41.2 dBm even at 12.1 dBm POUT, meeting regulatory requirements.

Alternative Performance Indices-Based Control Technique for a Unity Power Factor Three-Phase Rectifier

The implementation of a unity power factor (UPF) three-phase rectifier has the potential to enhance the power factor (PF). However, the PF and total harmonic distortion (THD) experience degradation in low-output regions due to the utilization of a “critical input inductor” under rated load conditions. In this study, an analysis of the operation principle of a UPF three-phase rectifier is conducted and a reference compensation current technique based on alternative performance indices is proposed. The optimal control algorithm is utilized to calculate the single harmonic phase delay of each phase and determine the compensator gain, taking into account factors such as the single harmonic distortion limit, THD limit, PF, and active power consumption. The output of the current compensator serves as the desired current source, which in turn drives the bidirectional switches. The simulation and experimental results demonstrate that the proposed control technique can significantly mitigate power supply current distortion, and the input power factor has been effectively improved within a wider load range.

Fuzzy Logic Application of Steady-state Harmonic Distortion Limits for the Time-varying Harmonics

Harmonic distortion limits recommended by most international standards are designed for the steady-state harmonics, which are typically calculated for planning purpose. A problem can occur, however, when the limits are applied to actual time-varying harmonics. This paper proposes a new fuzzy logic application to apply modified steady-state harmonic limits using total demand distortion, which is recommended in the IEEE standard 519-1992, to the actual measured harmonic distortions which varies with time. Fuzzy logic application can provide simple and easy implementation and reflect experts’ knowledge. The result of fuzzy logic application indicates how close the current waveform is to a pure sinusoidal wave shape and also reveals whether this current harmonic distortion is within or outside the allowable limits. It is expected that this application can contribute for future developments of harmonics monitoring, evaluation, and mitigation strategies in the actual operating status of power system.

A New Approach in Defining Harmonic Indices in Power Utility Application

This paper proposes a new method for current harmonic evaluation. Several harmonic indices have been defined for this purpose among which the Total Harmonic Distortion (THD) is the most widely used one. However, all these indices suffer from some deficiencies such as giving the same weight to all harmonic orders, and not giving a clear relation between the harmonics and their effects on system equipment. In this paper, for the first time, an index is defined based on current harmonic effects on transformers and power lines. A new formula is defined in order to determine the share of each harmonic order. The paper also proposes a new harmonic limit for the derived index. The limit is based on the de-rating of a transformer subjected to harmonic environments in order to keep its life equal to that of the same transformer when handles only fundamental current. In order to compare the effectiveness of the new index, several real cases with the same THD level are evaluated using the proposed index.

Multi-objective optimization of planning single-tuned harmonic filter utilizing interactive forest algorithm

This paper proposes an interactive forest algorithm for planning single-tuned harmonic filters for electric power distribution systems. The planning of harmonic filters is a complex problem that must consider multiple objectives, including minimizing the total cost of installed filters and the individual and total harmonic distortion while adhering to operational constraints, such as the voltage drop, the current loading and the harmonic limits. Moreover, system perturbations must be considered, such as frequency variations. This paper proposes a new method for multi-objective optimization of planning single-tuned harmonic filters utilizing the proposed interactive forest algorithm with a non-differentiable multi-objective function involving continuous and discrete variables. A multi-objective optimization technique based on the proposed interactive forest algorithm is proposed. In the interactive approach, planners set expectations for each objective and use the forest algorithm to figure out the optimization problems. The results of the Pareto Front are analyzed and the answers are searched through the interactive process to identify a solution that meets the planner’s expectations, allowing for practical compromise or satisfactory solutions. A case study is reported to show the superiority of the proposed method.

Power Quality of PV Multilevel Inverters in Residential Environment

The aim of the paper is to perform a comparative analysis of power quality for several PV multilevel inverters operating in residential environments. Two cases are presented, namely a diode-clamped multilevel inverter and a cascaded H bridge multilevel inverter which are compared with the situation of a pure sinusoidal supply regarding the voltage, the current and the instantaneous power waveform shapes. The waveforms are synthesized and uploaded in a programmable power source and are applied to a 40 W / 459 lx LED luminaire load. The harmonic limits check according to the standard IEC 61000-3- 2:2018, Class C, regarding lighting equipment are also presented. The measurements revealed that a filter retrofitting method was needed in order to obtain compliance with the power quality standard requirements

Structural fluctuations in active glasses.

The glassy dynamics of dense active matter have recently become a topic of interest due to their importance in biological processes such as wound healing and tissue development. However, while the liquid-state properties of dense active matter have been studied in relation to the glass transition of active matter, the solid-state properties of active glasses have yet to be understood. In this work, we study the structural fluctuations in the active glasses composed of self-propelled particles. We develop a formalism to describe the solid-state properties of active glasses in the harmonic approximation limit and use it to analyze the displacement fields in the active glasses. Our findings reveal that the dynamics of high-frequency normal modes become quasi-static with respect to the active forces, and consequently, excitations of these modes are significantly suppressed. This leads to a violation of the equipartition law, suppression of particle displacements, and the apparent collective motion of active glasses. Overall, our results provide a fundamental understanding of the solid-state properties of active glasses.

The transatlantic divide: intermediary liability, free expression, and the limits of trade harmonization

Abstract Amid escalating apprehensions surrounding content regulation, the USA has discreetly integrated provisions reminiscent of its Communications Decency Act Section 230 (CDA 230) into trade agreements, offering broad immunity. This scholarly analysis critically assesses this manoeuvre by juxtaposing such CDA 230-like provisions against the UK’s established legal framework governing online content and freedom of expression. Utilizing a comparative legal methodology, the paper underscores the pronounced differences between the USA and UK stances on intermediary liability for third-party content, moulded by their unique constitutional foundations and jurisprudential interpretations of free speech rights. The insertion of CDA 230-aligned clauses into trade agreements poses a potential threat to the UK’s nuanced equilibrium between safeguarding free speech and upholding other paramount interests, such as privacy and reputation. An scrutiny of UK defamation statutes and content regulation protocols reveals inherent challenges in transplanting CDA 230 provisions into trade contexts. In summation, the paper ardently supports a diversified approach to online content governance and cautions against standardizing intermediary liability laws via trade agreements, especially between nations with divergent foundational beliefs. It fervently endorses a cross-disciplinary discourse involving both trade and legal specialists to ensure the preservation of free expression while concurrently recognizing the intricacies of crafting universally applicable standards for online platforms and content regulation.

Comparison of APF and STATCOM for Current Harmonic Mitigation

The application of solid-state electronic devices has recorded a geometric increase in the last decade. Devices such as battery charging systems, inverters, switch mode power supplies and a host of electronic-based devices referred to as non-linear loads distort the source signal (particularly the current). Harmonics distortion imposes a severe impact on the well-being of the power system. They cause excessive device heating, reduced performance efficiency, early insulation failure, decreased dynamic torque in rotating systems, etc. This paper bases a study on Active Power Filter (APF) and Static Synchronous Compensator (STATCOM) for mitigation of these distortive harmonics in a system of 3-phase 11kV/400V, 400kVA feeding a system of non-linear loads. The study is based on the IEEE519 standard limits for current harmonics measured at the PCC. Therefore, the system short circuit ratio (SCR) is first determined. Using synchronous reference frame and instantaneous reactive power theories, the APF and STATCOM are respectively designed and run using MATLAB/Simulink software. The result analysis is obtained from the FFT signal processing toolbox of the software, and the device’s performances are evaluated based on the set standard. Results from the FFT spectra showed that the model system contains a considerable number of harmonics before filtering. However, when these devices are connected to the system, all higher-order harmonics have been minimized to the least fractions with respect to the standard, with STATCOM giving a comparatively better performance.

Enhancing power quality and loss optimization in distorted distribution networks utilizing capacitors and active power filters: A simultaneous approach

The importance of Power Quality (PQ) issues in modern power systems has been growing in the last years. Capacitors are employed for optimizing network losses and increasing the voltage profile. However, in harmonic polluted networks, the placement of capacitors at their economic optimal locations may not be feasible due to harmonic constraints. Under such conditions, harmonic filters can mitigate harmonic pollution and enable capacitors to be optimally placed. This paper presents a novel approach for simultaneously optimizing the allocation of Active Power Filters (APFs) and capacitors, to improve the harmonic condition, network losses, and voltage profile of distribution networks. The method models APFs as harmonic sources in the Harmonic Power Flow (HPF) procedure, while capacitors are modelled as their corresponding harmonic admittance. Furthermore, a modified Particle Swarm Optimization (PSO) algorithm is presented as the optimization tool. Three case studies were conducted on the IEEE 18-bus test system. In the first study, optimal capacitor placement was performed with no regard to harmonic constraints, reducing network losses by 326 kW. The harmonic limits were then considered and satisfied by optimal APF placement. The total cost resulted in $241,983. The second study considered harmonic limits in the procedure of optimal capacitor placement, improving voltage profiles and network losses, but exceeding some harmonic constraints, which were subsequently satisfied by APF placement. The solution yielded the total cost of $264,942. The third study introduced simultaneous allocation of capacitors and APFs, proving to be the most cost-effective strategy ($225,417 total cost), promising enhanced network performance and efficiency, and adding valuable insights for future power system optimization.