Selective Harmonic Elimination Pulse Width Modulation Research Articles

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.

SHE PWM based 21 level inverters with hardware analysis

Recently, the advancement of multilevel inverters (MLI) has been a crucial factor in high power and medium voltage applications. This MLI has multiple topologies and has been used in a variety of applications. Cascaded MLI is preferred over other forms of multilevel inverter topologies. Nonetheless, significant obstacles are encountered when implementing these topologies. They necessitate an increased number of switches, DC sources, capacitors, and diodes. Increased losses and total harmonic distortion (THD) will be present in the system. In addition, the MLI is more expensive. The better construction of a multilevel inverter results in more output levels with fewer switches, sources, and driver circuits, as well as low THD. A new single-phase cascaded asymmetrical DC voltage sources based multilevel inverter design and the selective harmonic elimination (SHE) approach are used to attain these goals. After confirming in MATLAB/Simulink, the hardware implementation of the multilevel inverter in 21 levels was completed in this article.

A comprehensive review on recent trends and future prospects of PWM techniques for harmonic suppression in renewable energies based power converters

Research has concentrated on promoting the development of environmentally friendly energies since air pollution, energy crises, and global warming are main challenges in modern era. One effective way to reduce environmental damage is to use Renewable Energy Resources (RER). The prominence of RER is increasing due to escalating global energy challenges. Power converter development and application are closely associated to the deployment of RER. One major problem with these power converters is the presence of extremely high harmonic components in their output voltage. Various PWM techniques are employed to suppress harmonics and no singular PWM technique is universally applicable to all circumstances. Firstly, this review paper provides readers with in-depth explanation of the significance of harmonic suppression as well as presentation of several important PWM strategies. Then, the advantages and disadvantages are explored, and the methods are compared in terms of the number of harmonics suppressed by each PWM technique. Further, this review also discusses and describes harmonics suppression, PWM categorization, Single PWM, Multiple PWM, Sinusoidal PWM, Modified Sinusoidal PWM, SVPWM, Hysteresis PWM, Selective Harmonic Elimination PWM, and Multiple Carrier PWM, as well as their benefits and drawbacks. Tables with comparative assessment based on various parameters are provided for each PWM technique. Lastly, conclusion with a thorough presentation of future tendencies is provided.

Harmonic Elimination Using Grid Integrated Hybrid Renewable Energy System with Optimized Control for Nano Scale Based 31-Level MLI

This research focuses integration of grid integrated hybrid renewable energy system (HRES) with optimized control techniques for harmonic elimination using Nano Scale Based 31-Level Multi-Level Inverter (MLI). The proposed system combines Renewable Energy Sources (RES), such as Solar Photovoltaic (PV) and Wind Energy Conversion System (WECS) assisted with Doubly Fed Induction Generator (DFIG) to generate power for grid integration. Interleaved KY converter with novel Rain Optimized Algorithm assisted Artificial Neural Network (ROA-ANN) based Maximum Power Point Tracking (MPPT) is established, which is a hybridized approach extracting maximum PV power and optimizes power output for utilization. Excess energy generated from hybrid power sources is utilized to charge battery. The DC supply from hybrid sources is transferred to silicon carbide switches of 31 MLI for elimination of harmonics using Selective Harmonic Elimination Pulse Width Modulation (SHE-PWM). The 31-Level MLI facilitates conversion of DC voltage to AC with assistance of Particle Swarm Optimized Proportional Integral (PSO-PI) controller. Finally, controlled AC supply is transferred to LC filter, resulting in effective grid synchronization with reduced harmonics. The proposed system’s performance is validated using MATLAB Simulink, and obtained results demonstrate effectiveness with reduced total harmonic distortion (THD) of 0.66% in contrast to state-of-art approaches

Comparative Study of Advanced Modulation and Control Schemes for Dual Three-Phase PMSM Drives With Low Switching Frequencies

In this paper, multiple advanced low-switching-frequency modulation and control schemes are investigated for dual three-phase permanent-magnet synchronous motor (PMSM) drives. The modulation schemes under investigation include multisampling space vector modulation (MS-SVM), selective harmonic elimination pulse width modulation (SHEPWM) and synchronous optimal pulse width modulation (SOPWM) while the control schemes include complex vector control, model predictive control (MPC) and flux trajectory control-based model predictive pulse pattern control (MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C). The difference between three-phase and dual three-phase PMSM drives at low switching frequencies is analyzed. Moreover, an optimal pulse width modulation (PWM)-based MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C scheme is proposed for the dual three-phase PMSM, where the optimal PWM modulation and MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C control are combined such that the optimal steady-state and dynamic control performance is achieved among the modulation and control schemes investigated. Experimental results are given to compare and validate the proposed control scheme.

Controlled random initialization of search vectors for application of gravitational search algorithm to selective harmonic elimination PWM

The prime objective of SHE PWM is to eliminate selected lower order harmonic by solving a set of non-linear transcendental equation while maintaining the fundamental component at a desired satisfactory value. In order to solve these non-linear equations different metaheuristic optimization techniques has been used in recent past. Due to faster convergence rate increased precision and higher probability to calculus based mathematical approximation techniques. In this manuscript an improved initialized Gravitational search algorithm has been proposed for a uni-polar 3-phase inverter. The algorithm is improved upon through a controlled random initialization of search agent, specifically for the purpose of solving the set of non-linear transcendental equation in SHEPWM for 3- switching angles. The simulation of the gravitational search algorithm and the proposed improved initialized GSA has been performed in MATLAB software and comparison of different performance parameter like Harmonic distortion, convergence rate etc. has been studied. The simulation results proves that a considerable improvement has been achieved by applying improved initialized GSA algorithm in terms of harmonic mitigation, convergence rate and accuracy in finding out the appropriate switching angles. Finally, the results obtained in simulation are verified through an appropriate experimental setup.

Efficient control of three-phase cascaded multilevel Z-Source inverter using SHEPWM technique

This paper presents an enhanced control strategy for three-phase cascaded multilevel Z-source inverters, focusing on the implementation of Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) techniques to improve efficiency. Z-source inverters are gaining prominence in various applications due to their inherent advantages, such as increased voltage boost capability and inherent shoot-through protection. However, achieving optimal control in cascaded multilevel configurations poses challenges that this study seeks to address. The proposed control strategy optimizes the switching patterns of the inverter, thereby enhancing its overall performance. It allows for precise control over the output voltage and reduces harmonic distortion, ensuring the inverter operates efficiently across varying load conditions. The research methodology involves a comprehensive analysis of the proposed technique, including its mathematical modeling and simulation using advanced software tools. Performance metrics such as total harmonic distortion, efficiency, and transient response are evaluated to quantify the improvements achieved. The results obtained demonstrate the efficiency of the proposed control strategy. This method significantly reduces harmonic distortion in the output voltage, leading to improved power quality. Furthermore, the efficiency of the inverter is enhanced, making it suitable for applications demanding high-performance power conversion.

Selective Harmonic Elimination PWM Technique Based on Higher Order Sliding Modes: Generalized Formulation

Selective Harmonic Elimination PWM Technique Based on Higher Order Sliding Modes: Generalized Formulation

Common-Mode Voltage Suppression of a Five-Level Converter Based on Multimode Characteristics of Selective Harmonic Elimination PWM

The combination of five-level converters with selective harmonic elimination pulse-width modulation (SHEPWM) is a practical need in medium-voltage, high-power applications. However, how to suppress the common-mode voltage (CMV) in this case becomes a difficult problem. Although CMV suppression under high switching frequency (SF) modulations and three-level SHEPWM has been discussed in many studies, these methods are not applicable to five-level SHEPWM. This is partly because the zero-sequence voltage under SHEPWM is difficult to adjust and partly because the solution spaces of three- and five-level SHEPWM are completely different. Moreover, conventional CMV suppression in three-level SHEPWM must sacrifice the switching angles to control the zero-sequence voltage, which makes the equivalent SF increase. Therefore, in this article, we propose a novel CMV suppression method that effectively utilizes the multimode characteristics of five-level SHEPWM. Multimode characteristics refers to the output waveform containing different levels of jump patterns. Therefore, there are a large number of switching angle trajectories in five-level SHEPWM, which outputs the same fundamental voltage with different CMVs. The proposed method uses the special multimode characteristics to reduce the CMV without sacrificing the switching angles. Its effectiveness and feasibility are verified by experiments.

FC-PV-battery-Z source-BBO integrated unified power quality conditioner for sensitive load & EV charging station

The proposed integrated system combines of fuel cell (FC), photovoltaic (PV), battery, Z-source and Biogeography-Based Optimization (BBO) based Unified Power Quality Conditioner (UPQC) compensator aims to provide a high-quality power supply to sensitive loads, such as electrical, electronics, medical equipment, Electrical Vehicles (EV), or critical industrial processes. It can regulate voltage, mitigate power disturbances (e.g., voltage sags, swells, flicker, voltage interruption, harmonics, reactive power etc.), and ensure a stable power supply. Additionally, it can facilitate EV charging stations by managing the power flow and optimizing charging processes. The PV or FC based Z-source inverter can control and regulate power flow in both directions. It operates with a unique impedance network, allowing for voltage boosting or bucking. The Z-source inverter enhances the flexibility and control of power flow in the system. The fuel cell generates electricity through an electrochemical process, typically using hydrogen as a fuel source, while the PV array converts sunlight into electrical energy. The FC-PV system provides a renewable and clean energy source. The battery serves as an energy storage device within the integrated UPQC system. It stores excess energy produced by the FC-PV system or from the grid during off-peak hours and releases it when needed, contributing to load balancing and stability. Biogeography-Based Optimization (BBO)-based Selected Harmonic Elimination Pulse Width Modulation (SHE-PWM) technique calculate the proper inverter switching angles and control the total harmonic distortion (%THD). Grid connected EV charging station produce nonlinear current and pollute the DC-link system. The proposed FC-PV-Z source-BBO based UPQC and its control strategy can enhance the EV-charging induced PQ (power quality) issues, eliminate the voltage and current harmonic or reduce overall voltage and current %THD control the proper reactive power, improve the power factor, restoring the flicker, transient, swells and sags of the micro grid, grid or smart grid and completely moderate the fluctuations of DC-link voltage.

Power Management Systems for Harmonic Elimination Using Hybrid Artificial Neural Networks Approaches

This study proposes two neural network-based approaches for computing the degrees required to generate pulse-width modulation (PWM) signals. The conventional method of using a lookup table to determine the orientations is replaced by these ANN models, which demonstrate superior performance across a range of modification indices. The first ANN is trained to estimate the phase angle based on input from the Empire Bird Optimizer, eliminating the need for a lookup table. A separate ANN is then trained using these configurations to generate the PWM signals. Experimental data on voltage level, inverter output current, and power flow are collected using a scope and power quality tester. The recommended hybrid ANN-based selective harmonic elimination PWM effectively removes low-order vibrations. The research is implemented in the MATLAB/Simulink platform, and the results indicate that the proposed system is efficient, accurately determining firing angles with minimal repetitions, and effectively addressing local minima values. The practical implementation of an eleven-level modular multilevel converter serves as the basis for this proposal, exemplified by an eleven-level H-bridge inverter.

Simplified selective harmonic elimination PWM for three‐level five‐phase T‐NPC inverter

SummaryThis paper presents a selective harmonic PWM strategy (HSE‐PWM) to control a five‐phase three‐level T‐NPC inverter. The proposed method aims to reduce switching losses and directly eliminate specific orders of harmonics, while also controlling the fundamental magnitude. MATLAB/Simulink simulations are conducted using an RL load, and the implementation is tested using a simplified method on an STM32F4 controller board. Experimental tests are then carried out to validate the simulation results. Additionally, power losses and efficiency are studied using Plecs software. The paper explores four different cases of switching angles number and proposes three SHE methods: a simple SHE based on Newton Raphson's method, SHE with current THD optimization, and SHE with common mode voltage (CMV) optimization using the PSO algorithm. The proposed methods provide complete control over the fundamental of the output voltage and the selected harmonics while reducing switching losses. A comparison is carried out in terms of voltage waveform, maximum CMV, fundamental magnitude, total harmonic distortion (THD), and power efficiency for the three methods. The paper concludes that the proposed modulation can be useful in high‐power applications.

Online adaptive SHE algorithm for multilevel converters and implementation with embedded control system

Selective harmonic elimination pulse-width modulation (SHE-PWM) method has been widely used in various industrial multilevel converters befitting from low switching frequencies and precise elimination of low-order harmonics. Most of existing studies focus on accelerating calculation of switching angles or optimizing predictive neural networks. However, these offline methods cannot dynamically deal with the errors introduced by nonuniform dc sources of multilevel converters or biased placements of switching angles. This paper proposes an online adaptive SHE (OA-SHE) algorithm to compensate these errors. Errors caused by nonideal dc (NID) sources and leading-lagging placements (LLPs) are analyzed in detail. The error of output waveform is comprehensive result of NID sources and LLPs. By introducing feedback, the output waveform accuracy of multilevel converters can be increased greatly. Realization of the particle swarm optimization (PSO) with an embedded control system is presented to acquire good real-time performance. With the OA-SHE method, the value of particles has been higher than the initial value. High order harmonics, including 1st, 5th, 7th, 11th, and 13th components, are suppressed by the low-pass filter. Comparing to existing studies, this online algorithm does not need detailed model parameters and can be directly applied to practical applications achieving multi-objective optimization. Finally, both simulations and experiments are carried out to verify the effectiveness of this algorithm.

Runge–Kutta optimization‐based selective harmonic elimination in an H‐bridge multilevel inverter

AbstractThe application of iterative techniques for solving the Selective Harmonic Elimination Pulse Width Modulation (SHE‐PWM) problem, such as the Newton–Raphson (NR) method, can tend to get stuck at local optima in the solution space. Additionally, these methods may be sensitive to the initial value estimation of the solution. In contrast, metaheuristic approaches demonstrate resilience in seeking out the optimal solution. As such, this study utilizes the Runge–Kutta (RUN) metaheuristic optimization algorithm to demonstrate the SHE‐PWM technique in multilevel inverters (MLIs), including 5‐ and 7‐level modified H‐bridge (MHB) topology and a 9‐level asymmetric cascaded H‐bridge (CHB) inverter topology. The switching angles are obtained by varying the modulation index from 0.01 to 1.0 in steps of 0.01 for 5‐, 7‐, and 9‐level MLIs. The performance of the RUN algorithm in minimizing the total harmonic distortion (THD) value is verified through simulations in MATLAB/Simulink software. The superiority of RUN is established by comparing the results with state‐of‐the‐art metaheuristic algorithms, such as the Differential Evolution (DE), Genetic Algorithm (GA), and Grey Wolf Optimizer (GWO). Additionally, the switching angles obtained through RUN are validated by hardware experiments. According to the simulation and experimental results, the proposed RUN method exhibits better performance in terms of objective function values, algorithm robustness, fundamental harmonic magnitude, and THD values. The findings confirm the elimination of fifth harmonic, fifth, and seventh harmonics, and fifth, seventh, and ninth harmonics in 5‐, 7‐, and 9‐level MLIs, respectively.

Hybrid low switching frequency modulation strategy with high dynamic response for high‐power voltage source converter

AbstractFor high‐power converters, the low switching frequency (SF) modulation represented by selective harmonic elimination pulse width modulation (SHE‐PWM) is crucial to reduce the switching loss and enhance the efficiency with a good steady‐state performance. However, since the advantages of SHE‐PWM mainly come from the fixed switching angle distribution limited by non‐linear equations, switching angles should be adjusted slowly. This requires that the bandwidth of proportional integral (PI) controllers be limited hugely, resulting in a poor dynamic response. As the most popular control to improve the dynamic response, finite‐control‐set model predictive control (FCS‐MPC) has a worse steady‐state performance under low SF because of large errors caused by a long prediction period and harmonics caused by space vector PWM (SVPWM). Therefore, a hybrid modulation strategy with an acceptable complexity is proposed in this article, which combines SHE‐PWM and FCS‐MPC. PI + SHE‐PWM is adopted in a steady state with low SF, while MPC + SVPWM is used in a transient state with high SF. By studying smooth switching from the modulation level and control level, the proposed method can eliminate the current surge when switching between PI + SHE‐PWM and MPC + SVPWM. Experiments verify that the proposed method have a good steady‐state performance and high dynamic response simultaneously under overall low SF.

A strategy for improving the SHEPWM commutation speed of CSI through hybrid switches

High-power current source inverters (CSI) usually operate at a low switching frequency to reduce switching loss. To suppress low-order harmonics and simplify filter design, the selective harmonic elimination pulse width modulation (SHEPWM) technique is a feasible common modulation strategy in industrial applications. This paper proposes an operational strategy that uses an H7 current source inverter (H7-CSI) with hybrid switches to perform the SHEPWM technique. On the basis of retaining the conventional H6 inverter bridge, the commutation speed of the CSI is improved by an additional shunt-connected high-performance power switch. The proposed scheme solves the problem that the CSIs built with low-speed switches (such as GTOs) may have difficulty for implementing the setting pulse widths of null states, while further reducing the switching losses at an acceptable cost. In addition, mitigating the influence of overlap-time by optimizing the driving signal of the H6 converter bridge. Finally, simulation and experiments have verified the effectiveness of the proposed CSI scheme.

Individual Output Voltage Regulation Method of Multifrequency Multireceiver Simultaneous WPT Systems With a Single Inverter

Individual output voltage regulation is an important issue in the multireceiver simultaneous wireless power transfer system. To solve this issue, a novel output voltage regulation method based on a multifrequency modulator and multiple proportional–integral (PI) controllers has been proposed. The proposed modulator combines the improved selected harmonic elimination pulsewidth modulation (SHEPWM) technique and delta-sigma modulation (DSM) technique, which has much less number of switching actions in comparison with the existing multifrequency modulation methods. A continuous-time small-signal model of the system is derived to close the voltage loop. With the proposed method, the output voltages of the system can be regulated individually, continuously, and accurately just using a single inverter and standard receivers. Moreover, the proposed method can be easily extended to the system with more receivers. Finally, the effectiveness of the proposed method is verified experimentally.

Harmonics Elimination in 7-Level Multilevel Inverter Using Animal Migration Optimization Algorithm with Different Objective Functions

Harmonics can degrade the power quality of a multilevel inverter by causing the voltage to be distorted and vary from sinusoidal waveforms. Harmonics can be reduced by increasing the number of voltage levels or by employing suitable modulation techniques. In this paper, The Selective Harmonic Elimination Pulse Width Modulation (SHEPWM) modulation method is employed to obtain the optimal switching angles that able to reduce the specific individual harmonic and the Total Harmonic Distortion (THD) in singlephase 7-level Cascaded H-Bridge multilevel inverter. The Animal Migration Optimization (AMO) is proposed to acquire these angles using two difference objective functions. The performance is examined and evaluated. Both objective functions able to determine the optimal switching angles starting from modulation index of 0.34. However, the comparative study demonstratethat objective function number 2 has better performance in term of lowering selective individual harmonics as well as THD.

A review on technological aspects of different PWM techniques and its comparison based on different performance parameters

AbstractUse of Pulse Width Modulation (PWM) techniques has enabled the converters to be used in low‐frequency high‐power applications. The main objectives of PWM are to reduce the line current harmonic, switching energy loss, and torque pulsation and motor acoustic noise (for motor drive applications). This paper mainly deals with selective harmonic elimination PWM (SHEPWM), Hysteresis current controlled PWM (HCPWM), space vector PWM (SVPWM), bus‐clamping PWM (BCPWM), and the most advanced wavelet PWM technique (WPWM). Different conventional as well as advanced soft computing techniques have been discussed for SHEPWM in order to solve the complex non‐linear transcendental equations and obtain the optimized switching angles. The paper also deals with different conventional and advanced bus clamping sequences that have shown superior result in mitigating the switching loss. In order to judge the true performance of SHEPWM and CSVPWM in terms of accuracy of obtaining the switching angles, convergence rate, THD, torque ripple, switching energy loss, etc., a common experimental test bench consisting of three‐phase, two‐level, six switch inverter coupled with a 2 hp, 50 Hz, three‐phase induction machine has been formed. The selected BIA‐based SHEPWM and CSVPWM have been implemented in the MATLAB simulation software, and the same has also been applied to the experimental test bench through dSPACE 1104 DAC card. Performance of HCPWM and different BC‐PWM sequences has also been verified using the same experimental test bench. This manuscript will help the researches and practitioners working in this field, to gain a clear idea about the type of PWM to be used for their specific application in order to achieve superior performance.

Power Quality Improvement of a Reduced Switch MLI Using a Modified ANN-Based SHE Technique

A cross-connected source (CCS) based multilevel inverter (MLI) is proposed for the generation of “9” and 13-levels using asymmetrical switching. The reduced switch CCS-MLI is controlled with a low frequency selective-harmonic-elimination pulse-width-modulation (SHE-PWM) strategy. The switching angles are synthesized by solving SHE equations utilizing the proposed modified artificial-neural-network (ANN) like architecture. The ANN can solve multiple transcendental equations starting from random initial guess points and without any initial data. This adds a significant improvement to the existing techniques that suffer severely with an increased number of SHE equations to be solved. To verify these unique features of the modified ANN, a CCS-MLI is realized with a higher number of levels. The enhanced performance and reasonable convergence rate of the ANN validate the suitability of the proposed control. Furthermore, CCS-MLI is simulated for resistive-inductive load considering THD as a performance parameter. The power quality improvement of the proposed inverter is shown for different modulation index (MI) and significantly low THD is reported for both “9” and 13-level case. Experimental results of a hardware prototype are also illustrated. Furthermore, the proposed system is implemented as a central inverter of standalone PV system to test its practical feasibility.