Switching Angles Research Articles

Eliminating Inrush Current in Three-Phase Transformer using Artificial Neural Network

Transformers are important parts of an electrical power system. When a power transformer is connected to the grid, usually inrush current increases substantially with a high value of harmonic components with a duration up to many cycles. The amount of flux in the core increases causing the magnetic circuit to saturate due to the increasing in the load. This paper describes a technique to accurately predict the inrush current and third harmonic of three phase transformer. A shallow neural network was created. The input parameters of the artificial neural network were the magnetization resistance Rm, the initial flux of phase A and the switching angle q. The number of neurons has been changed in the code to see the best performance value. The best validation performance was at epoch 71 with a value of 5.3641e-05. A good prediction results were obtained using this ANN. The simulation of the inrush current was done using the MATLAB Simulink software.

Power losses analysis for reduced switch 9-level cascaded H-bridge multilevel inverter

This study provides a thorough examination of power losses and total harmonic distortion (THD) in single-phase 9-level cascaded H-bridge multilevel inverters (CHB MLI) at low switching frequencies. The aim is to analyze the efficiency of a single-phase 9-level cascaded CHB MLI using three distinct switch configurations: 16-switch, 11-switch, and proposed 8-switch. The calculated switching angles are optimized using the feed-forward methodology. Two types of load conditions—R load and R-L load—are being examined. The results suggest that the proposed 8-switch design exhibits superior efficiency by limiting power losses compared to other topologies. Regarding THD, the conventional topology yields a somewhat lower value, however, the disparity is less than 1% when compared to both reduced switch topologies.

ANFIS-PSO-Based Optimization for THD Reduction in Cascaded Multilevel Inverter UPS Systems

Uninterruptible Power Supplies (UPSs) protect electronic equipment by delivering consistent power. Among the core components of a UPS is the inverter, which converts stored DC energy from batteries into AC power. This work focuses on a cascaded multilevel inverter topology for its ability to reduce voltage Total Harmonic Distortion (THD), which is essential for maintaining UPS efficiency and power quality. Using an ANFIS (Adaptive Neuro-Fuzzy Inference System) model, enhanced with the Particle Swarm Optimization (PSO) algorithm, the switching angles were optimized to minimize THD. This work focused on an online UPS with a seven-level inverter structure powered by three LifePo4 S17 batteries, with critical load levels (100%, 95%, 50%, 15%, and 5%) represented in 35 experimental cases. The experimental design allowed the ANFIS-PSO model to adapt to varying voltages, achieving robust THD reduction. The results demonstrated that this combination of ANFIS and PSO provided effective angle optimization, with a low standard deviation of 0.06 between the training and simulated %THD, highlighting the process’s accuracy. The analysis showed that, in most cases, the simulated THD values closely aligned with, or even improved upon, the calculated values, with discrepancies not exceeding 0.2%. These findings support the ANFIS-PSO model’s potential in enhancing power electronics applications, particularly in critical sectors like renewable energy and power transmission, where THD minimization is crucial.

An Improved Type of Synchronized Space Vector PWM Based on Switching Angles for High‐Power AC Drive Application

Synchronized space vector pulse width modulation (SSVPWM) is widely employed in high‐power AC drive systems. The existing methods are carrier‐based, in which the carrier ratio, position of samples, and switching sequences used to generate every sample for a given SSVPWM are settled, which causes two problems: (i) the control delay changes, and a voltage phase modulation error appears suddenly during transition between different SSVPWMs with different carrier ratios, which causes motor current spikes; (ii) due to the particular switching sequences, some kinds of SSVPWM cannot get into six‐step operation by overmodulation. This paper proposes an improved type of SSVPWM based on switching angles, in which the carrier ratio of a given SSVPWM can change flexibly, and the problems mentioned above can be solved. Theories including switching angle calculation, overmodulation strategy, carrier ratio setting principle, and transition rules between different SSVPWM modes are given in this paper. Meanwhile, the switching angles change linearly with modulation index which makes it easy to implement, and the modulation error in the overmodulation region is effectively limited so that the proposed scheme is suitable in the whole modulation index range. A case study of a 5.5‐kW experimental platform is presented to validate the proposed method. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Quasi-modified-Newton method-based selective harmonic elimination in cascaded H bridge inverters

Multilevel converters have gained significant popularity in medium-voltage and high-power applications due to their numerous advantages over traditional two-level converters. These advantages include reduced harmonic distortion, improved efficiency, and lower stress on power semiconductors. Selective harmonic elimination (SHE) is a modulation method that can be employed with multilevel converters to achieve high-quality output voltage waveforms. In this work, an extension of Broyden’s method, known as the Quasi-Modified Newton Method, is implemented for selective harmonic elimination and accurate calculation of switching angles for a wide range of modulation indices. The proposed method is applied to cascaded H bridge inverters operating at levels 5, 7, and 9. The method offers simplicity, reduced computational burden, and faster convergence, making it easily implementable, reducing total harmonic distortion (THD), and reducing RMSE and MAD errors. The paper includes simulation and experimental results that validate the accuracy and effectiveness of the proposed approach.

Implementation of NLC‐SHM based novel PWM scheme on packed U‐cell multilevel inverter

AbstractThis article introduces a novel integrated nearest level controller (NLC) combined with selective harmonic mitigation (SHM) control approach aimed at efficiently suppressing lower‐order harmonics has been introduced. The proposed methodology is implemented on the PUC‐7 inverter topology, leveraging the combined benefits offered by both NLC and SHM controllers through a hybrid model. The proposed method demonstrates the capability to reduce lower‐order harmonics up to the 49th harmonic from the load voltage. The particle swarm optimization algorithm is employed to determine optimal switching angles and their corresponding nearest levels, thereby reducing implementation time, computational complexity, and overall system intricacy. The performance analysis of the proposed control strategy across various scenarios, including fluctuations in modulation index and monitoring diverse parameters such as load dynamics has been performed. This approach yields a significant reduction in total harmonic distortion in both load voltage and current. A comparative analysis between NLC, selective harmonic mitigation (SHM), and the integrated NLC‐SHM approach is carried out on the PUC‐7 inverter. The integrated SHM‐NLC control is implemented and validated using the MATLAB Simulink environment, complemented by hardware‐based experimentation, to ascertain its effectiveness.

A Novel NR-DA-Based ANN for SHEPWM in Cascaded Multilevel Inverters for Renewable Energy Applications

Harmonics is the major power quality problem caused by nonlinear devices, leading to malfunction or operational halt of the system. Low-order harmonics increase vibration and heat generation in motors. Therefore, controlling harmonics in the output waveform is the prime target for industrial applications to avoid economic loss. Selective harmonic elimination pulse width modulation (SHEPWM) is one of the techniques used for eliminating or minimizing selected harmonics in the output voltage waveform. This paper utilizes the Newton-Raphson method and Dragonfly Algorithms to calculate optimum switching angles for a Cascaded H-bridge Multilevel inverter (CHBMLI). The algorithms use non-linear equations to calculate the Switching Angles of MLI. The Dragonfly algorithm requires several iterations to reach an optimum solution. For complex problems, this algorithm becomes computationally expensive and time-consuming. A lookup table addresses the limitation by offline training an Artificial Neural Network (ANN) to generate the optimum switching angle for a given modulation index. Neural Fitting Tool in MATLAB software is used to train the ANN model. The simulation is performed using MATLAB SIMULINK software for both 5-level and 7-level CHBMLI configuration. The Dragonfly algorithm-based ANN achieves THD 8.84% when the modulation index (M) equals 0.8 for a 7-level inverter and THD 14.91% for a 5-level inverter and effectively minimizes third and fifth-order harmonics.

Real-time harmonics optimization of seven level converter for megawatt scale solar PV-utility integration

This paper presents a new single photovoltaic (PV) array fed cascaded H bridge (CHB) submodule based three-phase 10 MW solar photovoltaic (SPV) plant for medium voltage utility applications. Each submodule comprises of a single PV array, cascaded H bridge cells and line frequency transformers. A 10 MW seven level converter based solar PV plant is realised with four submodules feeding solar PV array power to 33 kV grid. In megawatt scale multilevel converters based configuration, semiconductor switches experience reduction in voltage stress and requirement of high switching frequency for gating for switches is eliminated. Moreover, an efficient single stage MPPT based decoupled controller is implemented with genetic algorithm inspired fundamental frequency switching. GA based optimization technique is used to calculate optimal switching angles in offline mode. Obtained switching angles are incorporated to achieve closed loop optimized decoupled control of SPV system. Lower order harmonics are eliminated and power is fed to grid at enhanced power quality. This large scale PV system is modelled in MATLAB-Simulink and simulated results are validated in real time.

Performance Enhancement in LC Series Resonant Inverters with Current-Controlled Variable-Transformer and Phase Shift for Induction Heating

This article presents an analysis of a converter based on an LC resonant inverter for induction heating applications. It employs a current-controlled variable transformer (VT) in conjunction with phase shift regulation (PS) to operate at a fixed frequency close to the resonance frequency. The converter maintains a small switching angle, enabling substantial load variations without sacrificing zero voltage switching (ZVS) for the transistors. This innovative method enhances the inverter’s performance across the entire operating range. Additionally, a new design of the transformer structure with a variable ratio will be analyzed, enabling mathematical modeling. The obtained results demonstrate a performance exceeding 99%. Both the inverter and variable transformer designs were experimentally validated using a 15 kW, 200 kHz converter for induction heating applications with silicon carbide (SiC) MOSFETs.

Algorithm for Assessment of the Switching Angles in the Unipolar SPWM Technique for Single-Phase Inverters

Algorithm for Assessment of the Switching Angles in the Unipolar SPWM Technique for Single-Phase Inverters

Wavelet scattering and multiclass support vector machine (WS_MSVM) for effective fault classification in transformers: a real-time experimental approach

The dependable operation of the protective system is affected by residual magnetism and magnetic bias during the activation of the transformer. Challenges arise in distinguishing between inrush current and fault current when the transformer circuit breaker switching angle and remnant flux attain specific values. This situation can lead to a lack of sensitivity or failure in the operation of the transformer protection system. Thus, this paper proposes an effective approach for classifying different faults in transformers (internal and non-internal faults) using wavelet scattering and multiclass support vector machine (MSVM) technique (WS_MSVM). The wavelet scattering method begins by transmitting the data through a sequence of wavelet transforms, nonlinear operations, and averaging processes. This series of operations aims to generate low-variance representations of time series data. Wavelet time scattering produces signal representations that remain unaffected by shifts in the input signal, while still preserving the ability to distinguish between internal and non-internal faults. Internal faults are those occurring within the zones of the current transformer (CT) connected on both sides of the transformer. On the other hand, non-internal faults consist of magnetizing inrush current, sympathetic inrush current, and external faults (faults occurring outside the CT zones). The efficacy of the proposed WS_SVM is evaluated on the real-time experimental results obtained from the differential path of a laboratory transformer. The experimental data generated over one power frequency cycle under diverse operating conditions is employed in MATLAB to assess the effectiveness of the proposed WS_SVM algorithm.

An enhanced current chopping control strategy for SRM drives using Harris Hawks optimization algorithm

This research proposes an Optimized Current chopping Control (CCC) approach for SRM drives. The goal is to implement a simple SRM drive that can effectively meet electric vehicle requirements, comprising minimized torque ripple to reduce vibrations and acoustic noises, maximized output torque to enhance vehicle acceleration, and improved efficiency, which contributes to extending the EV's battery life. Therefore, an optimization problem is formulated and solved offline, incorporating a CCC-based SRM drive model. The control variables for this optimization problem are the switching angles of the SRM. A multi-objective function is chosen to combine three performance indices: torque ripple, average torque, and efficiency. The Harris Hawks Optimization (HHO) method is utilized in this paper to solve the optimization problem and find the optimal switching angles based on the selected objective function. HHO demonstrates a strong search capability that can effectively handle the nonlinear magnetization characteristics of SRMs. Constraints on the switching angles are also included in the optimization problem to control the phase current's RMS value and power consumption. The optimized switching angles are applied to a current chopping control (CCC) strategy and an asymmetric half-bridge converter to implement the proposed HHO-based CCC drive. Moreover, to demonstrate the effectiveness of the proposed HHO-based CCC drive, a comparative analysis based on simulations and experimental measurements is presented against other CCC approaches for SRM drives, including modified particle swarm algorithm (MPSO)-based CCC drives and analytical-based CCC drives.

Analysis of Cascaded Asymmetric Inverters using Low Frequency Technique

Multilevel inverters include a wide range of configurations and numerous benefits. Since each level switching angle is not neatly prepared, most conventional inverters cannot produce optimized waveforms. To attain an adequate voltage profile, we should indeed closely review the switching angle arrangement to attain a minimal Total Harmonic Distortion (THD). This work focuses on Cascaded H Bridge (CHB) multilevel inverters with asymmetrical configuration operating under a low frequency (LF) scheme. This work discusses various methods of harmonic mitigation techniques that comes under the LF scheme which includes the finest switching angle optimizations for generating various levels. Furthermore, the effectiveness of the topologies is investigated by minimizing lower-order harmonics and THD. THD is compared for various mitigation techniques for seven and nine-level configurations. The proposed configurations are simulated by employing MATLAB/Simulink. THD is calculated theoretically and evaluated by comparing it to simulated results for the suggested inverters. Additionally, thermal simulations of the configuration are carried out in PLECS to estimate power losses and efficiency. The suggested configurations are examined utilizing OPAL-RT (4510) test bed and the outcomes are included.

Switching‐angle‐based hybrid modulation method of full wind speed and low carrier wave ratio for direct‐drive permanent‐magnet wind power generation system

AbstractA switching‐angle‐based hybrid modulation method of full wind speed and low carrier wave ratio for direct‐drive permanent‐magnet wind power generation system is proposed here, which order to improve the control performance of wind turbines in the full wind speed range. The combination manner of the proposed method is based on the harmonic distortion rate of the stator current, a modulation mode with a higher carrier wave ratio is adopted within the maximum switching frequency allowed by the system, the switching angle from optimized synchronous modulation also is introduced. In order to solve the problem of current impact caused by switching different modulation modes, the switching strategy between different modulation modes is developed from the perspective of harmonic current. And the sectors are redivided for the problem of sudden change in carrier wave ratio during switching, which improve the control effect of permanent‐magnet synchronous wind generator when changing the modulations modes. Finally, the feasibility and correctness of the proposed method are verified by theoretical analysis and simulation.

Domain reorientation due to smectic layer instability in high tilt angle-based surface stabilized ferroelectric liquid crystal cell

High tilt angle (45°) ferroelectric liquid crystal (FLC) in surface stabilized geometry, having no chiral smectic A (SmA∗) phase, has been studied for the reorientation of the smectic layers near the transition temperature (Tc). The electro-optical studies have shown the stripe domain formation in which the liquid crystal molecules are aligned along the rubbing direction, but the smectic layers are tilted away from the rubbing direction at room temperature. In such high tilt angle FLCs, the molecular alignment and smectic layer formation start from bottom and top rubbed grooves at Tc. The domain formation of the FLC takes place in the middle of the top and bottom surfaces due to the frustration of the dipolar interaction. The smectic layer switching is observed by optical microscopy and confirmed by the dielectric spectroscopy method near Tc of SmC∗ and chiral nematic phases. Domain switching has shown a larger switching angle than the molecular tilt angle within the smectic layer. These studies are expected to be significant for understanding the smectic layer structure and the domain switching process, which may pave the way for large optical switching devices.

The Implementation of Space Vector PWM in 36-Pulse D-STATCOM for Power Quality Improvement

Introduction: This paper addresses the ongoing challenge of harmonics reduction in power systems, particularly focusing on Flexible AC Transmission Systems (FACTS) devices. Instead of employing a conventional multilevel converter, an alternative configuration is proposed: a 36-pulse gate turn-off thyristor-based converter (GTO-VSC). This converter comprises three 12-pulse Voltage Source Converters (VSCs) as fundamental units, operating collectively on the frequency mode of GTO switching control within a Distribution Static Synchronous Compensator (D-STATCOM). The D-STATCOM dynamically compensates reactive power in the system. The 36-pulse configuration results in AC output voltage waveforms containing harmonics such as the 35th, 37th, 71st, 73rd, etc., leading to higher total harmonic distortion (THD) levels. background: Reduced number of switches in flexible AC transmission. Method: In response, the paper presents a new model featuring a 3-level, 36-pulse, 25kV, ±3MVAr STATCOM configured with 12-pulse GTO-VSCs. This model incorporates PWM gate switching and employs a PI-control methodology to optimize harmonics in simulation, specifically targeting harmonics at the 35th, 37th, 71st, 73rd, etc., orders using Sim Power Systems toolbox in Math Works software. Result: The compensator's operational performance is controlled through switching angle optimization, which minimizes harmonics, regulates voltage, and manages reactive power in the electrical transmission system. Conclusion: The simulation results demonstrate that the proposed model is acceptable for enhancing the flexibility and performance of the FACTS device in mitigating harmonics in power systems.

Interior-point-method-based switching angle computation for selective harmonic elimination in high-frequency cascaded H-bridge multilevel inverters

Interior-point-method-based switching angle computation for selective harmonic elimination in high-frequency cascaded H-bridge multilevel inverters

A grey wolf optimization-based modified SPWM control scheme for a three-phase half bridge cascaded multilevel inverter

The Multilevel inverter (MLI) plays a pivotal role in Renewable Energy (RE) systems by offering a cost-effective and highly efficient solution for converting DC from Photovoltaic (PV) sources into AC at high voltages. In addition, an innovative technology holds immense significance as it not only enables the seamless integration of PV systems into the grid but also ensures optimal power generation, thereby contributing to the widespread adoption of RE and fostering a sustainable future. This paper presents a modified sinusoidal pulse width modulation (SPWM) control scheme for a three-phase half-bridge cascaded MLI-powered PV sources. The selection of the MLI configuration is motivated by its reduced number of switching components, which enhances system reliability and simplifies experimental implementation. Compared to the SPWM schemes which require (m−1) carriers that make the generation of the pulse circuit very complex, the proposed control scheme requires only three signals: a carrier signal, a triangular waveform, and a modulating signal. This approach significantly reduces the complexity of control and facilitates practical implementation. The proposed control scheme simulation is verified using MATLAB/SIMULINK Software. The grey wolf optimization (GWO) algorithm is implemented to determine the optimal switching angles of the proposed control scheme. The Total Harmonic Distortion (THD) objective is selected to be the fitness function to be minimized for improving the quality of the output waveforms. For verification, the results of the proposed GWO-based modified SPWM control scheme are compared with those obtained using both the Particle swarm Optimization (PSO) and Genetic algorithm (GA) used in the literature. Simulation results declared that the proposed control scheme improves performance, especially THD which is minimized to 6.8%. Experimental validation has been conducted by building a laboratory prototype of the proposed system. The experimental and simulation results gave acceptable and limited convergent results considering the experimental difficulties.

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.

Selective harmonic elimination in PUC‐5 multilevel inverter using hybrid IGWO‐DE algorithm

AbstractThe use of a multilevel inverter has received significant attention in recent years due to its numerous advantages. Because of the widespread use of multilevel inverters in industries and applications that require a wide range of voltages, achieving high‐quality voltage has presented a number of challenges. Many studies have been carried out to address the problem of unwanted harmonics in multilevel inverters. The inverter switching can be done at a low frequency using the Selective Harmonic Elimination (SHE) technique, and the unwanted harmonics can be significantly reduced; however, the issue with SHE is solving the transcendental equations and determining the optimum switching angle. To address this problem, a new and improved hybrid algorithm is proposed that combines two evolutionary algorithms, gray wolf optimization (GWO) with an improved and new convergence factor and Differential evolution (DE) with a dynamic scaling factor using a crossover operator. In this paper, the optimum switching angles for a packed U cell 5‐level inverter are estimated using the proposed algorithm for distinct modulation index values, and simulation results are compared with different algorithms. The simulation result of the proposed algorithm, IGWO‐DE is confirmed through experiment.