Selective Harmonic Elimination Method Research Articles

CSA-based harmonic elimination controlled reduced switch multilevel inverter for standalone PV system

A standalone photovoltaic (PV) system has emerged as a clean energy solution for application in remote areas. To establish such a system a suitable converter is required for voltage boosting as well as to produce high-quality output as required by the load. To achieve this, multilevel inverters (MLIs) are the proven substitute in PV systems. A conventional MLI uses multiple sources and switches that increase the cost and complexity. To provide a complete stand-alone system solution that addresses this issue, reduced component switched capacitor (SC) based seven-level MLI is disclosed in this paper. A new crow search algorithm (CSA) based selective harmonic elimination (SHE) method is employed to estimate the switching angles. The dominant harmonic orders are removed from the 7-level SC-MLI output while the desired firing angles for the switches are evaluated. Using only seven switches, the circuit boosts the voltage to 1.5 times with the aid of self-balanced capacitors. Therefore, the circuit does not require an additional control circuit for voltage balancing. The overall system is designed in MATLAB/Simulink environment to test under different operating conditions. An experimental prototype of the 7-level SCMLI is also designed to validate the CSA-based SHE control and MLI performance in real time.

A hybrid search space reduction algorithm and Newton–Raphson based selective harmonic elimination for an asymmetric cascade H-bridge multi-level inverter

Abstract In this paper, a selective harmonic elimination (SHE) method for an asymmetric cascade H-bridge multi-level inverter (ACHB-MLI) has been performed by using hybrid search space reduction and Newton–Raphson (SSR-NR) algorithm. Three H-bridges are cascaded in a single phase configuration, while each of the bridge is fed with V dc , 3V dc and 6V dc respectively. This particular asymmetric combination of dc sources will produce 10 possible switching combinations and 21-levels in the output voltage ranging from −10V dc to +10V dc . Hence, there will be 10 SHE equations corresponding to fundamental and harmonics, and the solution will be the 10 switching angles which satisfy those SHE equations. While traditional gradient-based techniques like the Newton–Raphson method can yield the global optimal solution for the SHE equations, they necessitate an initial guess. Conversely, meta-heuristic methods often face challenges related to sub-optimal convergence. To address these issues, a novel the hybrid SSR-NR algorithm has been introduced in this paper. This method combines stochastic and deterministic elements, offering a promising solution for solving the SHE equations. In the first step, the evolutionary SSR algorithm will be used and the output of the SSR algorithm is given to the NR method as an initial guess to converge to the final solution, this way the proposed hybrid SSR-NR algorithm is able to address the drawbacks of both the algorithms such as initial guess requirement for NR method and sub-optimal convergence characteristics of evolutionary algorithms. The simulations were carried out in Matlab/simulink environment for a 21-level ACHB-MLI. The results obtained showcase the efficacy of the proposed SSR-NR algorithm in solving the SHE equations. For demonstrating the effectiveness of SSR algorithm the results were also compared with other algorithms such as particle swarm optimization and grey wolf optimizer as well. Further, the experimental results on a laboratory prototype using dSPACE DS1104 R&D controller board were also presented in the paper, to validate the proposed methodology.

GWO-NR Hybrid Method for Selective Harmonic Elimination in Multilevel Inverter for Distributed Energy Systems

GWO-NR Hybrid Method for Selective Harmonic Elimination in Multilevel Inverter for Distributed Energy Systems

Red deer algorithm-based selective harmonic elimination technique for multilevel inverters

This paper proposed a red deer algorithm (RDA)-based selective harmonic elimination (SHE) method for multilevel inverters (MLIs). To eliminate the desired harmonic orders, the optimum switching angles of the MLI have been calculated using the proposed RDA. The calculated switching angles have been applied to the 3-phase cascaded H-bridged 11-level inverter. In addition, the performance of the proposed RDA method was compared with the results of methods such as the Newton-Raphson (NR) method, LSHADE/EpSin technique (LSHADE), whale optimization algorithm (WOA), and particle swarm optimization (PSO) used for the SHE problem in the literature. The results obtained prove that the proposed RDA optimization solves the SHE problems more effectively than other methods. It has also been observed that RDA produces good solutions in different modulation indexes.

Investigation of Recent Metaheuristics Based Selective Harmonic Elimination Problem for Different Levels of Multilevel Inverters

Multilevel inverters (MLI) are popular in high-power applications. MLIs are generally configured to have switches reduced by switching techniques that eliminate low-order harmonics. The selective harmonic elimination (SHE) method, which significantly reduces the number of switching, determines the optimal switching moments to obtain the desired output voltage and eliminates the desired harmonic components. To solve the SHE problem, classical methods are primarily employed. The disadvantages of such methods are the high probability of trapping in locally optimal solutions and their dependence on initial controlling parameters. One solution to overcome this problem is the use of metaheuristic algorithms. In this study, firstly, 22 metaheuristic algorithms with different sources of inspiration were used to solve the SHE problem at different levels of MLIs, and their performances were extensively analyzed. To reveal the method that offers the best solution, these algorithms were first applied to an 11-level MLI circuit, and six methods were determined as a result of the performance analysis. As a result of the evaluation, the outstanding methods were SPBO, BMO, GA, GWO, MFO, and SPSA. As a result of the application of superior methods to 7-, 11-, 15-, and 19-level MLIs according to the IEEE 519—2014 standard, it has been shown that BMO outperforms in 7-level MLI, GA in 11-level MLI, and SPBO in 15- and 19-level MLIs in terms of THD, while in terms of output voltage quality, GA in 7-level MLI, BMO in 11-level MLI, GA and SPSA in 15-level MLI, and SPSA in 19-level MLI come forward.

Optimum regulation of THD profile in multilevel inverter using parameter-less AI technique for electrical vehicle application

This article proposes investigation on harmonic profile improvement using a novel fitness function in the multiphase multilevel inverter. For the proposed study in this paper, three-phase, seven-level cascaded H-bridge (CHB) multilevel inverter (MLI) is considered. Modulation of the stepped waveform output of the MLI is done using selective harmonic elimination (SHE) method. Many algorithms are proposed for solving the set of nonlinear transcendental trigonometric equations for SHE methods. Teaching learning-based optimisation (TLBO) algorithm is a parameter less optimisation technique. Due to the lack of controlling parameters, the proposed algorithm is most robust among the family of artificial intelligence (AI) techniques. In this paper, an investigation is carried out on a novel fitness function proposed for controlling total harmonic distortion (THD) for the proposed inverter. It is observed that the proposed fitness function improves THD profile below IEEE standards. It is also observed that THD profile obtained through this method is far better than THD profile obtained through various proposed methods so far. The results of THD profile from the MATLAB Simulink simulations are verified experimentally using seven-level three-phase hardware controlled by Arduino MEGA 2560 low-cost controller.

Harmonic reduction using Particle Swarm Optimization based SHE Modulation Technique in Asymmetrical DC-AC Converter

Many inverters play an important role in transmitting and processing energy to power system networks. To reduce the cost and size of multilevel inverters, various topologies have been included in the literature. But these topologies do not look at the complete harmonic distortion in the output waveform. In this study, a modern multilevel inverter structure, a mutated H-bridge inverter is adopted that demands a small amount of switches, driver circuits, power diodes and DC voltage sources compared to conventional multilevel inverters to produce the required level in the output voltage. The mutated H-bridge converter uses a nearest-level control method, produces high value of total harmonic at the output voltage and low-level harmonics content is also high, which is more dangerous than high-order harmonics. Therefore, the selective harmonic elimination (SHE) method is used to reduce the low frequency harmonics and the total harmonic distortion to the output voltage. Comparison of complete harmonic deviation and low-level harmonic content using the above-mentioned control strategies on the 31-level inverter is presented. Simulation studies confirm the performance of a 31-level inverter with low-order harmonics and a complete harmonic distortion using the SHE process. The effectiveness and accuracy of the SHE in producing 31 level waveform is demonstrated by utilizing the test outcomes and the THD found is of the order of 2.8%, 1.7%, 1.7% and 1% for the modulation index values of 0.5590, 0.7440, and 0.8380 and 0.9110 respectively.

Design and Development of a B-Type Inverter for Harmonic Mitigation in a Grid Integrated System Using Whale Optimization Algorithm

This paper introduces a B-type inverter and an improved Y source DC-DC converter that use a selective harmonic elimination (SHE) method based on whale optimization to inject power into the grid with reduced harmonic content. The suggested topology contains four unidirectional switches, two bidirectional switches and three DC sources to produce the required output voltage level. The proposed topology can be functioned with equal and unequal DC sources. The developed structure can generate the negative voltages without the use of an H-bridge. It has more redundant states, and it is partially fault tolerant in nature. The proposed structure provides a high value of level to switch ratio. A single input multiple output high gain modular Y-source DC-DC converter is implemented for effective utilization of the PV modules in the suggested system. The triggering angles for the suggested system is generated using the SHE based whale optimization algorithm (WOA). Using the SHE-WOA method a total harmonic distortion (THD) of is obtained. The developed system is integrated with the grid and for grid synchronization PI based WOA method is used. Simulation study has identified the presence of only 2.47% of harmonics in the grid current and 2.03% in experimental analysis. Both these harmonic distortions are less than the IEEE-519 standards.

Modified Multiverse Optimizer Selective Harmonic Elimination for Five-Level Modified Packed U-Cells Inverter and Analysis of Motor Torque Ripple Suppression

A selective harmonic elimination method of modified packed u-cells (MPUC) inverter fed induction motor built on modified multiverse optimizer (MMVO) algorithm is put forward. The proposed method adopts the MMVO algorithm to search the optimal solution in the SHEPWM equations through the two processes of exploring the optimal solution distribution and exploiting the optimal solution within it. On this basis, the influence of the different orders of power supply harmonics eliminated selectively on the motor’s torque ripple is compared and analyzed by using the Simulink and MAXWELL. From the results of simulation and experiments, it can be proved that the method can achieve the required fundamental voltage and selectively suppress the harmonic with particular order. At the same time, it is verified by ANSYS MAXWELL that the working quality of the motor can be improved by selectively eliminating the 5th, 7th, 11th, and 13th harmonics in the power source to effectively suppress the 6th and 12th periodic torque ripples that arise from these harmonics.

Selective Harmonic Elimination for Variable Frequency Traction Motor Drives Using Harris Hawks Optimization

In this article, Harris hawks’ optimization (HHO) for selective harmonic elimination method (SHEM) of a voltage source inverter has been applied to a traction motor drive for light rail transportation. The main objective of SHEM's pulsewidth modulation (PWM) strategy is to remove the low-order harmonics by solving nonlinear equations while satisfying the required fundamental component's magnitude. The HHO applied in this article to a two-level, three-phase inverter aims at solving the associated nonlinear equations with a high accuracy and convergence probability as a strong metaheuristic algorithm. SHEM simulations are carried out via MATLAB/Simulink on a 125 kW traction motor drive platform for various SHEM angles to verify its performance in comparison with the SHEM with sinusoidal PWM (and space vector modulation (SVM) techniques. Experimental results obtained on a physical simulator of the light rail transportation system in the laboratory have shown remarkable findings in view of the dc-link voltage magnitude on the performance of the associated traction motor drive. In the light of different fundamental frequency operations, number of SHEM angles, and operating dc-link voltages, a general evaluation of the SHEM has been made in considering its application to a light rail traction motor drive. It has also been shown that the application of online SHEM on a GPU framework is possible in real-time.

Pareto optimization of multilevel inverter structures regarding the DC magnitude, switching frequency and switching angles

Due to several advantages over conventional inverters, multilevel inverters (MLIs) have been increasingly investigated for the automotive sector in recent years. Therefore, this publication proposes the design optimization of a cascaded H-bridge MLI for vehicle applications under three different control strategies; a sinusoidal pulse-width modulation (SPWM), a selective harmonic elimination (SHE) method as well as the combination of both, an SHE-PWM scheme. Besides the voltage magnitude of each submodule, also the switching frequency and switching angles are optimized depending on the respective modulation technique. Because of the typical opposing relationship of inverter losses and total harmonic distortion (THD), the Pareto front is used to solve this multiobjective optimization problem. Subsequently, the optimized MLI designs are compared for a dynamic driving profile. The comparison shows that the SPWM-MLI configuration with a number of 10 modules and a frequency modulation index of 162 outperforms the other two MLI designs obtaining an averaged THD reduction of more than a factor of two. All three optimized MLIs achieve an efficiency above 92.5%. Furthermore, a traditional SPWM-based three-level inverter cannot keep up with the SPWM-MLI in terms of distortion and inverter efficiency.

Design of a Partial Resonant Inverter for solar photovoltaic applications

This paper presents a solar-powered Partial Resonant Inverter (PRI) interfaced with an asymmetrical cascaded nine-level inverter. The DC input of the proposed system is obtained using Solar Photovoltaic (SPV) panel. The input DC sources fed to the asymmetrical cascaded nine-level inverter are in the ratio of 1:3. The step modulated nine-level inverter works with a precalculated switching angle for a fixed modulation of 0.7. Compared to the conventional 50 Hz inverter and the multi-output transformer design, the proposed system is more compact because of the high-frequency AC link. The PRI ensures Zero Voltage Switching (ZVS) and reduces the switching losses. The proposed scheme has been validated in the MATLAB/ SIMULINK environment and an experimental prototype is built in the laboratory. Based on the investigations the Selective Harmonic Elimination (SHE) method gives superior performance when compared to the Optimal Harmonic Stepped Modulation (OHSM) method. From the results and comparative analysis, the proposed system uses fewer switches to obtain the nine-level output, uses the PRI setup with the multioutput transformer to make the design compact and improves the power quality of the system.

THD Minimization in Cascaded H-Bridge Inverter using Optimal Selective Harmonic Elimination

Cascaded structured multilevel inverters are gaining lot of importance due to their simple structure and easiness in implementation. In this paper, the optimum selective harmonic elimination method is employed for a nine level inverter to suppress the selected lower order harmonic, which reduces the total harmonic distortion of the inverter considerably. The Newton rapson algorithm is employed in finding the switching angles that minimizes certain lower order harmonics. The order of the harmonics that are eliminated are third, fifth, and seventh harmonics. All the simulation results included for a nine level inverter using SIMULINK. Index Terms: Nine level MLI, Control of inverter, Modular Inverter.

D STATCOM Control using SRFT Method for PQ Improvement in a PV System

The set of restrictions defined for a system’s electrical characteristics so that the entire electrical system can function in the intended manner and without losses is known as power quality. Power quality issues such as transients, harmonics, voltage swell, sag, flicker, fluctuations, and power factor difficulties are becoming more common as power electronic devices become more widely used. The usage of a Distribution Static Compensator (D-STATCOM) to mitigate power quality issues is discussed in this study. In this case, D-STATCOM functions as a shunt active power filter to reduce harmonics caused by non-linear loads. The simulation studies on a PV-based Cascaded-H-Bridge Multi-Level Inverter i.e Solar PV and Cascaded H Bridge MLI are integrated using Selective Harmonic Elimination method with D-STATCOM injected at the load side to improve power quality are presented in this project. The Solar PV system is mathematically modelled using Boost regulator and P&O MPPT technique and to the D-STATCOM the controller is designed utilizing Synchronous Reference Frame Theory (SRFT) out of many control strategies for reactive power compensation, harmonic mitigation, and power factor enhancement as it is more accurate. A 2nd order low pass filter is employed at the load side to reduce the harmonics to some extent, and both 5-level and 7-level models are evaluated. MATLAB/SIMULINK is used for simulation.

RPWM selective voltage harmonic elimination method for single‐phase five‐level MPUC inverter based on cell division

The conventional selective harmonic elimination method of random pulse width modulation (RPWM) is only suitable for the two-level inverter. Furthermore, when the harmonics below 6 kHz are selectively eliminated, it is easy to cause a low average switching frequency of the inverter, which leads to the increase of load current distortion rate. This paper proposes an RPWM selective voltage harmonic elimination method for a single-phase five-level MPUC (modified packed U-cells) inverter based on cell division. The MPUC inverter is supposed to be divided into three series cells, and the carrier stacking strategy is used to realize the coordinated control between each cell. In the process of RPWM, the average switching frequency can be controlled within a certain range by selecting the random number. This method is divided into normal mode and master–slave mode. In the normal mode, the selective harmonic elimination is realized by the method of cancelling the front and back terms of Fourier series in each cell. In the master–slave mode, the master cell is mainly used for fundamental power output, and the slave cell is mainly used for RPWM selective harmonic elimination. The effectiveness of the proposed method is verified by the simulation and experimental results.

Selective harmonic elimination in multi-level inverters by using neural networks

In this study, it is aimed to eliminate the harmonics selected by the selective harmonic elimination (SHE) method in a 7-level cascade multilevel inverter using artificial neural networks (ANNs). A control algorithm has been developed in which the 3rd and 5th harmonics or 5th and 7th harmonics can be eliminated according to the selection while adjusting the output voltage amplitude of the inverter. The required switching angles for SHE are calculated in real time using ANN. These angles were first obtained offline training of ANN using Newton-Raphson method. ANN was trained in MATLAB® environment according to the obtained data. The resulting ANN algorithm and practical implementation using the STM32F429 ARM microcontroller® and inverter switching was provided. Experimental results of the system with RL load were tested.

A Novel RPWN Selective Harmonic Elimination Method for Single-Phase Inverter

In the existing random pule width modulation (RPWM) selective harmonic elimination methods, the formula of switching cycle TN+1 is complex, and the duty ratio DN+1 of the next switching cycle needs to be calculated in advance. However, in the case of unknown TN+1, DN+1 is also difficult to calculate accurately, and the two parameters are based on each other. A novel selective harmonic elimination method in RPWM is proposed in this paper. The PWM voltage pulse is placed at the back of the switch cycle, which simplifies the formula of the switch cycle TN+1 and eliminates the need to calculate the duty ratio DN+1. Two kinds of RPWM selective harmonic elimination ideas are summarized. The general formulas of the switch cycle, the effective random number k, and the upper and lower limits of switch frequency corresponding to k are derived. The spectrum shaping of inverter output voltage can be realized without using digital filter in this method. Simple algorithm, small calculation and easy implementation are characteristics of the proposed method. The simulation and experimental results confirm the ability of the proposed method for reducing harmonics at the specific frequency in power spectral density (PSD).

Design and Simulation of a Novel Nine Level Inverter Topology for Motor Application

In the couple of years, the demand of multilevel inverter has expeditiously increased in the field of utilization of electrical energy. Because the multilevel inverter is a key technology to integrate the different renewable energy sources (wind, solar etc) with the grid. In this research work, authors have configured a novel topology of nine level multilevel inverter has less number of switches with dc voltage sources. The presented approach has been designed to 9-level inverter with seven unidirectional switches with voltage sources. It comprises of an H-bridge which synthesize to ac voltage by utilizing almost all possible additive and subtractive cases of the voltage sources with its combinational power switches and generated optimal firing angles using selective harmonic elimination method with Genetic Algorithm to decrease the lower order harmonic present in the output voltage of the, which supplied by the presented nine-level inverter. It has been concluded that presented approach use a less number of power switches in drive circuit and the number of dc voltage sources also make a simple circuit and enhance the efficiency of the complete system.

Selective harmonic elimination method for unequal DC sources of multilevel inverters

This paper presented an analytical and closed-form solution for the harmonic contents that were injected in the five-level inverters from asymmetrical DC sources or batteries which were suitable for renewable energy sources. In the five-level inverters, two DC sources V1 and V2 were used to synthesize the output voltage. Therefore, two transcendental equations were formulated for the fundamental and the third harmonic orders based on the unequal DC sources V1 and V2. These transcendental equations were solved analytically for low switching control technique. The proposed solution included the modulation index change which resulted in changing the fundamental component. Therefore, two switching angles are formulated and solved analytically to control the amplitude of the fundamental voltage and cancel the third order harmonic. A well-known third order equation was generated. Thus, a closed-form solution for the above two switching angles will be generated in terms of the modulation index. The proposed solution was tested for a wide range of V1/V2 ratio. Some selected simulation and experimental results were provided to validate the proposed method for wide ranges of both modulation index and V1/V2 ratio.

Generalized Formulations and Solving Techniques for Selective Harmonic Elimination PWM Strategy: A Review

Multilevel inverters (MLIs) are widely recommended for DC to AC power conversion as per the load requirements. The MLIs are preferred over other types of multilevel and conventional converters due to their ability to produce staircase output voltage waveforms with superior harmonics profile. However, the performance of MLIs largely depends on the modulation strategy employed. Among the various modulation techniques, the selective harmonic elimination (SHE) method is more efficient in eliminating low-order harmonics from the voltage waveform produced by MLIs. Proper mitigation of the dominant low-order harmonics results in reduction in switching losses in the semiconductor devices and improves the efficiency of the inverter. However, the analytical solution of the nonlinear SHE equations constitutes the main challenge. Over last few decades, various solving algorithms and techniques such as algebraic methods such as resultant theory, numerical techniques and optimization algorithms have been developed and proposed for selective elimination of unwanted harmonics. This review paper presents the various aspects of the problem formulations for SHE technique. Moreover, the detailed principle operation for five different SHE problem-solving techniques is also discussed in this paper. Solution trajectories corresponding to multiple solutions, PWM waveforms with single and multiple transitions at each voltage level and also for pulse-width-amplitude modulation are evaluated and presented to help the researchers gain better insight into the SHE problem and its solution.