Voltage Total Harmonic Distortion Research Articles

Design and analysis of soft-switching and small-signal model grid-connected micro-inverter based on staggered parallel connection

Grid-connected micro-inverters, known for their straightforward wiring and operational stability, have garnered increasing interest from both industry and academia. However, the operational inefficiency of conventional inverters, the issue of distorted output waveforms, and the safety concerns with alternating current (AC) and direct current (DC) safety isolation limit the wide availability and utilization of micro-inverters. In order to overcome this problem, this research proposes a circuit topology consisting of two flyback circuits connected in parallel on the primary side of the transformer for safe isolation. Additionally, soft switches are incorporated into the flyback circuit at the front stage, with a voltage total harmonic distortion (THD) of less than 3.0 %. This study also develops a small-signal model to help with obtaining the current loop parameters. Parametric design and simulation studies with PLECS software confirmed the circuit architecture and control technique's accuracy. A 600 W prototype's design, analysis, and experimental validation are described. The proposed inverter has an efficiency of up to 97.2 %. The design and control methods employed in this paper offer a conceptual framework and engineering reference for relevant research and practical applications.

Investigations on solar PV integration and associated power quality challenges in distribution systems through the application of MCS and GA

In the forthcoming decades, significant advancements will shape the construction and operations of distribution systems. Particularly, the increasing prominence of photovoltaic (PV) systems in the power industry will impact the security of these systems. This study employs Monte Carlo Simulation (MCS) in conjunction with genetic algorithm (GA) and differential evolution (DE) to address uncertainties. The probability density functions (pdf) for total voltage harmonic distortion (UTHD), individual voltage harmonic distortion (UIHDh), and RMS voltage (URMS) have been determined for utilization in chance constrained framework. In addition, the uncertainty effects of PV systems on grid losses for various solar radiation conditions are also investigated. Specifically, the paper aims to evaluate these impacts within the context of stochastic limits. The PV system sizing problem has been addressed inside the distribution system using a chance-constrained framework. A key contribution is the integration of GA, DE, and MCS into a cohesive approach, and the study evaluates the benefits of this approach through an analysis of outcomes derived from the stochastic method. The simulation results illustrate the advantages of the proposed stochastic GA methodology.

An improved nested 3-phase 5-level MLI design with optimized output voltage and total harmonic distortion

Multilevel Inverters (MLIs) have advanced progressively and demonstrated enormous capacity in power electronics. To provide a 5-level voltage output with a 3-phase full-bridge arrangement and an additional bi-directional switch, a dc voltage input was split by two capacitors. This setup has two issues namely the output voltage limiting the magnitude of the input supply voltage and the voltage disparity between the isolating capacitors. This study suggests an improved nested 3-phase 5-level MLI design with a voltage level and total harmonic distortion (THD) that are both optimized. The suggested arrangement has the features of a lower proportion of passive elements and separated DC sources as it is constructed with a cascade linking of nested two-level cells (NTCs). The suggested unit cell was found to produce a 9-level output voltage (line) by producing a 5-level output voltage (phase) with a peak value that is double the level of the input voltage. The output voltage increasing the capacity of the suggested circuit is its prominent advantage, and the efficacy of the suggested design is 95% and validated by the simulated resultsKeywords: Multilevel Inverters (MLIs), Total harmonic distortion (THD), Voltage level.

Multilevel inverter: harmonic analysis with and without filters for RL load using SPWM techniques

Multilevel inverter (MLI) gains more attraction compared to conventional inverter as it generates a staircase output voltage that mimics sine waves of desired output voltage. Cascaded H-bridge (CHB) topology is taken into consideration owing to several benefits over conventional inverters. Various levels of CHB (3 and 5 level) inverters are compared on diverse parameters. In this paper level shift sinusoidal pulse width modulation technique is considered resulting in reduced lower order harmonic (LOH) distortion and improve the quality of output current and voltage depending on the load. Since, the LOH are too dangerous for power electronic circuits. An attempt to shift all the LOH above 50th order depending on the modulation technique with analogy for selecting an appropriate switching frequency is highlighted. The effect of change in switching frequency and modulation index (MI) on RMS output voltage, % voltage total harmonic distortion (VTHD), output power factor with different modulation techniques such as phase disposition pulse width modulation (PsD PWM), phase opposite disposition (POD PWM), alternative phase opposition disposition (APOD PWM) is portrayed in the paper. Further, to boost the performance a unique filter circuits with optimal design values of Inductance and capacitance driven with IEEE 519-2022 standards. The effectiveness in terms of with and without filter is verified and validated using MATLAB.

Performance of Bidirectional ON-Board Charger in Electric Vehicle: A Review

As per present technological advancement increment of electric vehicles (EVs) in public and private transportation is inevitable. Also, most of the EVs carry batteries as energy transaction/storage units. Generally, it can be observed that, mostly in the case of private vehicles, EVs are in an idle state for a longer time during corresponding office hours. So, these EVs can potentially be utilized for transmitting power from the batteries to the grid during the peak load condition of the grid. During the off-peak period of the grid, the batteries of the vehicles can be charged. To achieve this to-and-fro power flow of the batteries bidirectional converters (BC) play a significant role. In this regard, a high volume of research has been carried out to improve the design and topology of the BC to obtain highly efficient EVs. Therefore, it is eminent to review topologies used in BC. This paper discusses single phase single stage isolated, single phase two stage isolated, single phase two stage non-isolated, three-phase single-stage isolated, three-phase two-stage isolated, three-phase single-stage non-isolated, DC-DC isolated, and DC-DC non-isolated converters. Moreover, analysis about the performance of the converter topology based on parameters such as a wide voltage range, power density, efficiency, power factor, and total harmonic distortion are discussed. Furthermore, this extensive review delves into comparing various configurations of BC to provide insights into selecting the most suitable converter for a specific application.

Comparative evaluation of Z source / quasi Z-source direct and indirect matrix converters for PMG based WECS

The present era sees the dominance of wind energy conversion systems as a leading technology in renewable energy. Various technologies have been devised to harness wind energy, with variable speed systems emerging as particularly advantageous. Consequently, these systems are designed to operate at specified speeds using power electronic interfaces, maximizing power extraction from the wind. The integration of Permanent Magnet Generators (PMGs), directly linked to the wind turbine lacking a gearbox, allows operation at minimum speeds. To stabilize the continuously fluctuating output voltage of the PMG, power electronic converters are extensively utilized in Wind Energy Conversion Systems (WECS), ensuring a consistent voltage and frequency output. The voltage gain of Traditional matrix converters (MCs) is limited to less than 0.866. In turn, the Z-source (ZS) and discontinuous QZSDMC, as well as ZS IMCs, topologies have achieved voltage gains exceeding 0.866. However, the former provides complicated commutation issues from DMC, while the latter incorporates a Z source network in the DC link, resulting in a non-all-silicon solution. A novel continuous QZSDMC and QZSIMC are suggested, wherein a qZS network incorporates the grid-side filtering function. This design eliminates the need for an additional input filter in the proposed system. Three newly introduced topologies of ZSDMC, QZSDMC and QZSIMC are thoroughly compared across various parameters including voltage gain, current and voltage ripples, inductor current and capacitor voltage stresses, filtering capabilities, input current, and output voltage Total Harmonic Distortion (THD), finally efficiency. The paper presents their control and modulation methods to achieve the desired performance levels. Experimental comparisons validate the theoretical analysis and demonstrate the potential of the proposed QZSDMC as a promising topology.

Power quality improvement of PWM AC Chopper fed capacitor run induction motor using BFO, PSO and CSO Algorithm

This paper exhibits performance enhancement of PWM AC chopper fed capacitor run induction motor by using optimization algorithm. The PWM AC chopper utilizes enhanced asymmetrical pulse width modulation technique by incorporating four pulses in quarter cycle. The switching instants are obtained optimally by bacteria foraging optimization, particle swarm optimization and cuckoo search optimization algorithm. The power quality parameters considered in this paper are total harmonic distortion of current, total harmonic distortion of voltage, power factor and efficiency. The simulation result shows that proposed algorithm shows better performance compared to other optimization techniques.

Single-Phase Robust Charger with High Power Quality for Electric Vehicle Application

The widespread use of electric vehicles (EVs) necessitates the development of a robust charging infrastructure. The goal of this research paper is to create a high-quality, single-phase charger for electric cars. The purpose of this design is to provide a charger that is both fast and efficient but also protects against power quality problems including harmonics, power factor correction, and voltage variations. A single-phase–single-stage improved power quality EV charger for small and medium power applications has been designed and simulated. A single DC-DC converter is utilized for constant charging and improved power quality operation. The charger presented exhibits improved power quality as sinusoidal current is drawn from the utility grid supply with the total harmonic distortion (THD) in compliance with the IEEE 519 and IEC 61000-3-2 standards. In order to charge the battery of an electric vehicle, most two-stage converters first use a boost converter for power factor correction (PFC), and then they use a DC-DC converter that can accept any input voltage. These two-stage conversions are inefficient and use more parts than necessary. This work proposes a PFC converter based on a single-stage switching inductor Cuk converter, which has the advantages of high step-down gain, low current stress, high efficiency, and a small number of components. The suggested converter’s operational analysis and design equations are performed in continuous current mode. The proposed converter is the subject of extensive mathematical modelling, analysis, simulation, and experimentation presented in this study. With both constant voltage (CV) and constant current (CC) loads, the proposed converter’s performance is analysed with regard to power quality indices like voltage total harmonic distortion (THD), current THD, and total power factor. Additionally, in CV mode and CC mode, the suggested converter’s dynamic performance with battery charging is evaluated in relation to the extensive supply changes. The developed charger presents a reliable and efficient solution for EV charging, fostering the transition to a cleaner and more sustainable transportation system.

Determination of Optimal Locations and Parameters of Passive Harmonic Filters in Unbalanced Systems Using the Multiobjective Genetic Algorithm

This paper discusses the problem of optimal placement and sizing of passive harmonic filters to mitigate harmonics in unbalanced distribution systems. The problem is formulated as a nonlinear multiobjective optimisation problem and solved using the multiobjective genetic algorithm. The performance of the proposed algorithm is tested on unbalanced IEEE 13- and 37-bus three-phase systems. The optimal solutions are obtained based on the following objective functions: 1) minimisation of total harmonic distortion in voltage, 2) minimisation of costs of filters, 3) minimisation of voltage unbalances, and 4) a simultaneous minimisation of total harmonic distortion in voltage, costs of filters, and voltage unbalances. Finally, an analysis of the influence of uncertainties of load powers and changes in system frequency and filter parameters on filter efficiency was performed.

Even‐Order Harmonic Distortion Observations During Multiple Geomagnetic Disturbances: Investigation From New Zealand

AbstractLarge geomagnetic storms are a space weather hazard to power transmission networks due to the effects of Geomagnetically Induced Currents (GICs). GIC can negatively impact power transmission systems through the generation of even‐order current and voltage harmonics due to half‐cycle transformer saturation. This study investigates a decade of even‐order voltage total harmonic distortion (hereon referred to as Even‐Order Total Harmonic Distortion (ETHD)) observations provided by Transpower New Zealand Ltd., the national system operator. We make use of ETHD measurements at 139 locations throughout New Zealand, monitored at 377 separate circuit breakers, focusing on 10 large geomagnetic disturbances during the period 2013–2023. Analysis identified 5 key substations, which appeared to act as sources of ETHD. The majority of these substations include single phase transformer banks, and evidence of significant GIC magnitudes. The ETHD from the source substations was found to propagate into the surrounding network, with the percentage distortion typically decaying away over distances of 150–200 km locally, that is, at a rate of −0.0043 %km−1. During the study period some significant changes occurred in the power network, that is, removal of the Halfway Bush (HWB) single phase bank transformer T4 in November 2017, and decommissioning of the New Plymouth substation in December 2019. Decommissioning of these two assets resulted in less ETHD occurring in the surrounding regions during subsequent geomagnetic storms. However, ETHD still increased at HWB with increasing levels of GIC, indicating that three phase transformer units were still susceptible to saturation, albeit with about 1/3 of the ETHD percentage exhibited by single phase transformers.

Power quality assessment and compliance of grid-connected PV systems in low voltage networks using microinverters

AbstractSolar PV has experienced unprecedented growth in the last decade, with the most significant additions being utility-scale solar PV. The role of grid inverters is very critical in feeding power from distributed sources into the grid. With the increasing growth of grid-tied solar PV systems (both rooftop and large-scale), the awareness of power quality issues has risen with new regulations and standards to ensure the stability of the power grid. The power quality of microinverters has been investigated under steady solar irradiation and PV power source and also under real outdoor conditions in compliance with the accepted solar PV integration requirements. The current total harmonic distortion (THD) measured for the studied microinverter under outdoor conditions far exceeded the current THD for the study under steady indoor conditions and was beyond the accepted standard. However, the voltage THD outputs for the two studied cases were in good agreement with the grid codes. The voltage and current THD for the 400 Wm−2 (60 Wp) and the 1000 Wm−2 (146 Wp) scenarios under the steady solar irradiation (solar PV power) were 2.24%, 13%, and 2.27, 6.93%, respectively. The voltage and current THDs for the outdoor study were 2.03% and 14.28% for Solarex (pc-Si module), 1.94%, and 27.43% for Juta (mc-Si modules), and 1.97% and 33.6% for Dunasolar (a-Si glass module). Results showed a strong correlation between the intermittence of solar radiation and the current THD. 67%, 54%, and 37% of the recorded power factor for Dunasolar, Juta, and Solarex modules, respectively, exceeded the limits prescribed by the standards.

Integration of electric vehicle into smart grid: a meta heuristic algorithm for energy management between V2G and G2V

Recently, Electric Vehicles (EV) have been providing fast response and substantial progress in the power generation model. Further, EVs are exploited as adaptable Energy Storage Systems (ESSs) and show a promising performance in ancillary service markets to increase the demand of Smart Grid (SG) integration. The expansion of Vehicle-to-Grid concept has created an extra power source when renewable energy sources are not available. Yet, numerous operational problems still are required to be considered for EV implementation to turn out to be extensive. Even the development of Photo-Voltaic (PV) technology creates a problem in SGs when used for EV charging. Because of this, the Energy Management System (EMS) is required to handle charging requirements and deal with the intermittent generation. Here, in this research, an Improved Honey Badger algorithm (IHBA) is proposed for integrating SGs with EV parking lot, solar panels, and dynamic loads at the Point of Common Coupling (PCC). The proposed IHBA uses a dynamic programming method to optimize the charging Grid-to-Vehicle (G2V) or discharging Vehicle-to-Grid (V2G) profiles of the EVs using the forecasts of PV generation. This algorithm considers user preferences while also lowering reliance on the grid and maximizing SG effectiveness. The study’s findings show that the Honey Badger method is efficient in resolving issues involving large search spaces. The developed method is used to optimize charging and discharging of EV which is tested in MATLAB to obtain a stable load profile. From the evaluation of obtained results, it is evident that the IHBA controller outperforms the WOA and EHO controllers in terms of total harmonic distortion voltage (3.12%), power loss (0.197 kW) and efficiency (98.47%).

Intelligent Solar PV Grid Connected and Standalone UPQC for EV Charging Station Load

The insertion of renewable energy sources into the grid, as well as the development of power electronics technology to regulate loads that are not linear, had an impact on power quality (PQ). This study focuses on the PQ enhancement of grid-connected and standalone solar PV systems (SPVS) with battery energy storage device (BESD) for the Electric vehicle (EV) charging station (EVCS) load in addition to the local load. Here, a hybrid control strategy that uses both the superior qualities of the sliding mode controller (SMC) and the fuzzy logic controller (FLC) is suggested for the unified power quality conditioner (UPQC's) shunt filter. It's major goal is to achieve steady DC capacitance voltage (SVDC) during load (like EVCS, non linear balanced/unbalanced etc.) and irradiation variations, diminish of total harmonic distortion (THD) in source current and load voltage, and mitigate sag, swell disturbances, and source voltage unbalances. The created model's performance is assessed using two scenarios (grid and island) under four case studies with varying combinations of loads and grid voltage circumstances. However, to establish the superiority of the proposed technology, comparative research with standard technologies such as proportional integral controller (PIC) and SMC controllers is required. THD is reduced by the proposed method to 2.25 %, 2.36 %, and 1.71 %, It is inferior to the current approaches found in the survey.

Control strategy for power factor correction circuits based on model predictive control

Power factor correction circuits are being used more extensively, and with that, the requirements and standards have become increasingly stringent. To improve the power factor of the circuit, thereby improving its operational efficiency and mitigating the load effects in boost power factor correction circuits, reducing Total Harmonics Distortion is crucial for improving the quality of the current. An improvement upon the conventional dual-loop PID control algorithm has been proposed. It involves integrating Model Predictive Control into the current loop design and incorporates a Luenberger observer. Model Predictive Control methods can be applied for the control of multivariable systems, especially in complex multivariable systems, as they exhibit strong robustness. Finally, by performing both simulation and experimental validations and analyzing the data results, it is shown that under full load conditions, the power factor λ is 0.968, the efficiency η is 91.11%, the voltage total harmonic distortion Uthd is 1.88%, and the current total harmonic distortion Ithd is 7.04%. These data results strongly confirm the performance of the control mechanism proposed in this paper.

Assessment of voltage harmonics' impact on the maximum load capacity of the power supply transformer for the LHCD system.

To study the influence of the voltage total harmonic distortion (THDV) and its spectrum on the harmonic loss factor (FHL) and the maximum allowable load capacity ratio (Imax (pu)) for the transformer of the LHCD system, we use MATLAB software to model the LHCD system and study the winding loss and maximum allowed load capacity of the LHCD system transformer when the supply voltage source is sinusoidal and non-sinusoidal, respectively. The calculation is carried out by the method of IEEE standard C57.110 and the method of considering the skin effect. The calculation results of both methods clearly show that the THDV value of the supply voltage has a significant effect on the harmonic dissipation factor (FHL) and the maximum allowable load capacity ratio (Imax (pu)) of the transformer. And the calculation method considering the skin effect increases the maximum allowable load capacity ratio of the LHCD system transformer by about 2%. The research results have important reference value for the future retrofit design of LHCD system transformers.

Power quality investigation with multilevel inverter by photovoltaic-fed dynamic voltage restorer

ABSTRACT In this research endeavor, a novel approach has been presented to enhance the power quality through a Photovoltaic (PV)-based Dynamic Voltage Restorer (PV-DVR). The proposed work is designed to address voltage fluctuations, flicker, and harmonics within medium or low voltage micro-grid systems. Unlike existing DVR systems that often neglect injected harmonics and converter losses, in the proposed work there is an integration of a PV-fed multilevel inverter system employing Selected Harmonic Elimination and Moderation-based Pulse Width Modulation (SHEAM-PWM). This innovative configuration, coupled with a DC – DC boost converter and a series injection transformer, not only aims to alleviate voltage stress on devices but also optimizes the number of switches to minimize switching losses. The proposed setup successfully reduces the overall voltage Total Harmonic Distortion (THD) to a significant extent, delivering superior dynamic performance. To determine optimal switching angles for the SHEAM-PWM technique, ensuring the elimination or mitigation of the maximum number of harmonics from the output voltage waveform, we employ the Biogeography-Based Optimization (BBO) approach. The computation of these angles is performed offline to eliminate lower-order harmonics, and the results are stored in the microcontroller’s memory using mixed model equations for online applications. The efficacy of our proposed method is demonstrated through both simulation and experimental validation in a real-time laboratory system. The simulation and experimental results obtained underscore the potential utility of our technique for Dynamic Voltage Restorer (DVR) applications, particularly those requiring low harmonic injection. The proposed method introduces a comprehensive and innovative solution for power quality enhancement, combining PV technology, multilevel inverter systems, and advanced optimization techniques. The proposed PV-DVR system exhibits promising results, showcasing its potential for practical implementation in residential micro-grid systems with a focus on minimizing harmonics and ensuring efficient grid compensation.

Compensating voltage waveform distortions using a practical topology of series active power filters

Addressing harmonics, voltage sags, voltage swells, and asymmetrical variations is essential to seamlessly integrate renewable energy sources, electric vehicle charging stations, and power electronics devices into electric power grids. These issues can significantly impact the sinusoidal symmetry of voltage waveforms. Series Active Power Filters (APFs) present a promising solution that can dramatically improve power quality (PQ) by effectively addressing voltage distortions. This paper first identifies several topology-related impracticalities in the existing literature on series APFs, such as using nonlinear loads or linear loads with a current source. Secondly, to understand the motivations behind these impracticalities, commonly used reference extraction methods, namely, Instantaneous Reactive Power Theory (IRPT) and Synchronous Reference Frame (SRF), are tested on a practical topology consisting of a distorted voltage source and a linear RL load. Results conducted in the MATLAB/Simulink environment show that IRPT fails to extract the reference signal under the practical topology, and SRF leads to unacceptable THDs surpassing the 5% threshold mandated by relevant standards set forth for such applications. Thirdly, the matrix pencil method (MPM), a model-based parameter estimation technique that exploits a voltage waveform's underlying exponential signal model to extract the series APF's reference voltage, is proposed. Extensive simulations showcase the superior performance of the MPM-based series APF. It successfully reduces voltage total harmonic distortion (THD) to below 1.13% across various scenarios, including situations involving harmonic-polluted voltage sources, incorporating nonlinear loads, sag and swell phenomenon, and capacitor utilization in DC link implementation.

Real-Time Detection of Power Quality Disturbance Using Fast Fourier Transform and Adaptive Neuro-Fuzzy Inference System

Power quality disturbances cause equipment damage or financial losses. Therefore, the electric power system needs to identify and distinguish any power quality disturbances to reduce problems. This paper proposes hybrid methods combining FFT and ANFIS algorithm for detection of power quality disturbances. There are 11 types of power quality disturbances that can be detected, such as sag, swell, undervoltage, overvoltage, voltage flicker, voltage harmonic, sag + harmonic, swell + harmonic, undervoltage + harmonic, overvoltage + harmonic, and flicker + harmonic. The parameters used to detect disturbances are Vrms, Duration, THDv (Total Harmonic Distortion voltage), and Fluctuation-Count. The detection process starts by sensing voltage and calculating all the parameters, where THDv was obtained by Fast Fourier Transform. All the parameters such as Vrms, Duration, THDv, and Fluctuation-Count are processed by Adaptive Neuro-Fuzzy Inference System, and the result is the type of disturbance. Matlab simulations show that the suggested method performs outstandingly to identify 11 type of Power Quality Disturbances with 99.3% accuracy.

Comparing performance and complexity of TCHB and CHB multilevel inverters using NLC technique

This paper presents a modulation strategy applied to a 13-level three-phase transistor clamped H-bridge (TCHB) inverter, aimed at a renewable and electric vehicle drives application. A comparison is performed between the TCHB inverter and a traditional cascaded H-bridge (CHB) inverter, considering circuit complexity, switching losses, and total harmonic distortion (THD) attained from each multilevel inverter topologies. The TCHB inverter achieves a 13-level output with only 15 switches, whereas the conventional CHB inverter requires 24 switches. The modulation technique, employing a nearest level control, yields improved output quality for both the TCHB and CHB multilevel inverters. The results demonstrate that this strategy effectively minimizes the overall THD. Notably, previous modulation techniques mainly focused on carrier-based PWM or SVPWM, making this approach distinctive. The FFT analysis reveals a voltage THD of 5.49% for TCHB and 5.15% for CHB, indicating a marginal difference in THD content for each multilevel inverter. Despite the CHB inverter experiencing double the switching stress compared to TCHB, since less switches are required in the TCHB inverter, consequently, the system's total cost and complexity are reduced. The achieved results are verified through the use of simulations carried out in the MATLAB Simulink.

Harris Hawks Optimization Algorithm for reducing THD using ZVT-ZCT-based QRCC: A comparative approach

This study proposes a novel solution to address harmonic issues in a Renewable Energy Resource System (RES) connected to the grid, using a Voltage Source Inverter (VSI) controlled by a QRCC based on Zero Voltage Transition and Zero Current Transition (ZVT-ZCT). We enhance system performance by integrating Harris Hawks Optimization (HHO) with the VSI. Key outcomes include evaluating the system's effectiveness in terms of voltage drop, current drop, real power, active power, and total harmonic distortion (THD). Notably, settling times for various converters are highlighted: 0.01 s for SEPIC, 0.008 s for CUK, 0.005 s for ZETA, and an impressive 0.0001 s for the Cascade converter. Under different operational conditions, open-loop operation yields a THD of 18.45%, reduced to 7.843% in closed-loop with PI controller. Optimization techniques further improve the system, achieving a low THD of 0.0549%. We emphasize the significance of MPPT-based INC-IR for cascade converters, resulting in a minimal switching loss of 0.38W, showcasing the system's efficiency in energy conversion.