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Multilevel inverter (MLI) plays a crucial role in medium voltage and high power applications. While the usages of MLIs are continuously growing in every area of power industries, it also initiates certain challenges that require attention. The increased number of power electronic components is one of the most challenging issues for multilevel inver...
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... (N-R) method is proposed in this design for solving these equations. The proposed technique is executed in such a way that the odd harmonics (α1, α2, … α3n) can be eliminated under different ranges of modulation index (m) to produce the desired fundamental voltage. The staircase output voltage waveform of an NLevel inverter is illustrated in Fig. ...
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... Fig. 2, the output waveform is staircase therefore, the Fourier series expansion of the output voltage waveform can be written ...
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... (N-R) method is proposed in this design for solving these equations. The proposed technique is executed in such a way that the odd harmonics (α1, α2, … α3n) can be eliminated under different ranges of modulation index (m) to produce the desired fundamental voltage. The staircase output voltage waveform of an NLevel inverter is illustrated in Fig. ...
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Introduction. In recent years, a growing variety of technical applications have necessitated the employment of more powerful equipment. Power electronics and megawatt power levels are required in far too many medium voltage motor drives and utility applications. It is challenging to incorporate a medium voltage grid with only one power semiconducto...
In power electronic applications, especially high power and medium voltage, multilevel inverters (MLIs) have been commonly used. MLIs ensure high quality load voltage and lower Total Harmonic Distortion (THD) than traditional inverter. In this paper, a multilevel inverter structure with reduced number of power switches is proposed. The proposed mul...
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... In this work, an asymmetric MLI with a low switch count was developed, which eliminated the requirement for bidirectional switches, capacitors, and more diodes in the design of the MLI. Due to the absence of bidirectional switches, the proposed topology had no infuence on the reverse recovery times of the diode and voltage-balancing efect of input capacitors, and it makes use of a reduced gate control circuit to accomplish this [29][30][31][32][33]. Te suggested inverter employs a SHEPWM control approach to suppress the lower-order harmonics [34,35]. ...
... Using Newton-Raphson Method. Te seven switching angles for seven switches in the inverter are frst computed by a numerical successive approximation technique known as Newton-Raphson (N-R) approach [33]. Te computation of switching angles involves equations (6) with (7). ...
Multilevel inverters have great scope in current developments of grid-connected solar PV systems. Two-level inverters are the simplest kind of multilevel inverter available (MLI). As the number of output levels is raised, the total harmonic distortion decreases. In classic MLI topologies, more electronic components are utilized to get higher-level outputs, which raise the cost, complexity, and volume of typical MLI installations. By reducing the design components, the cost of the system will be reduced. Furthermore, the two-and three-level inverters produce constant dv/dt output, which increases the stress on the power switches. This research proposes an asymmetric MLI topology that is suitable for PV applications and utilizes less number of DC sources and switches. Te proposed inverter is controlled by selective harmonic elimination-based pulse width modulation (SHEPWM) to eliminate the lower-order dominant harmonics. Te nonlinear equations produced by the SHEPWM are solved for the switching angles of the proposed inverter using the Newton-Raphson (NR) method and particle swarm optimization (PSO) method for various modulation indexes. Te performance of the proposed inverter is analyzed based on the total harmonic distortion (THD) of the output for diferent operating levels of the inverter by comparing similar topologies in the literature. Te THD obtained by the NR method is 7.3% and by using PSO is 4.23% at 0.9 modulation index.
... Therefore, solution to the roots of transcendental equations will be unique values (notch angles) that are contingent on n level inverter. In this research paper, the roots of non-linear transcendental equations will be solved by means of traditional Newton-Raphson method due to following reasons [29], [30]. ...
This paper presents a detailed comparison of eliminated and non-eliminated harmonics for 3-level, 5-level and 13-level cascaded multilevel inverter. For this research, three different types of cascaded H-Bridge multilevel inverters are considered where each cascaded multilevel inverter generates a different output voltage, but the number of notch angles in all the three cases are kept identical. A unified approach is adopted to derive the mathematical model of each multilevel inverter output voltage waveform, RMS of output voltage, RMS of fundamental component, selective harmonic elimination system of equations for the low order harmonics elimination and output voltage total harmonic distortion. It is shown that since selective harmonic elimination system of equations can be expressed as a function of the notch angles, hence notch angles are determined while taking in account only those harmonics to be eliminated. The Newton-Raphson method is proposed to resolve the nonlinear transcendental equations of selective harmonic elimination for the three multilevel inverter cases. Consequently, once the notch angles are determined, all three multilevel inverters are analyzed by comparing Total Harmonic Distortion and Zero-Sequence Harmonics Factor. The elimination of triplen-harmonics by evaluating them in the non-linear transcendental system of equations is a significant contribution. The theoretical and simulated results are presented to verify the validity of the proposed work.
... By using Equation (8) to Equation (12), the Newton Raphson method can be done in the following steps [13] [14]. ...
A power inverter is an important device in present technologies since the usage of renewable energy sources has increased rapidly throughout the world. The main focus of research in the power inverter field is to produce a high-efficiency power inverter to maximize the energy harvested from renewable energy sources. In a power inverter, selecting an appropriate switching scheme is imperative. In this paper, two different switching schemes, namely the Nearest Level Modulation (NLM) and the Selective Harmonics Elimination (SHE) are implemented on the Cross-Connected Sources Multilevel Inverter (CCSMLI) circuit. The switching schemes are implemented on 11 and 13-level CCSMLI circuits with two types of loads (R load and RL load). The simulation results show that when applied to CCSMLI, both switching techniques' output voltage THD performances are comparable, but the NLM is paramount for high-level MLI topologies due to its simplicity.
... One of the major concerns is the analytical solution for determining the optimum switching angles [3], [4]. In literature, numerous techniques have been proposed such as; Newton-Raphson iterative approach [5]- [7], resultant theory-based approach [8], current reference-based approach [9], Walsh functions [10], gradient method [11], and meta heuristic optimization techniques [12]. In the Newton-Raphson (NR) approach, initial values need to be set. ...
... However, there is no established formula to select the initial values making the whole process highly unreliable and complicated. In addition, the optimization performance of NR is very sluggish, and it cannot produce wide range of solutions specially for lower-level MLIs [5]. Walsh functions for the SHEPWM was proposed in [10] to determine the optimum switching angles. ...
... Furthermore, because of implementing a balanced three-phase system, the triplen harmonics (3 rd , 9 th , 15 th . . . .) from the line voltage are also removed which has also contributed towards the reduction of the THD [5]. It should be mentioned that in a voltage source inverter, the dominant low-order harmonic are 3 rd , 5 th , 7 th , and 9 th [2]. ...
Selective harmonic elimination (SHE) technique is used in power inverters to eliminate specific lower-order harmonics by determining optimum switching angles that are used to generate Pulse Width Modulation (PWM) signals for multilevel inverter (MLI) switches. Various optimization algorithms have been developed to determine the optimum switching angles. However, these techniques are still trapped in local optima. This study proposes an opposition-based quantum bat algorithm (OQBA) to determine these optimum switching angles. This algorithm is formulated by utilizing habitual characteristics of bats. It has advanced learning ability that can effectively remove lower-order harmonics from the output voltage of MLI. It can eventually increase the quality of the output voltage along with the efficiency of the MLI. The performance of the algorithm is evaluated with three different case studies involving 7, 11, and 17-level three-phase MLIs. The results are verified using both simulation and experimental studies. The results showed substantial improvement and superiority compared to other available algorithms both in terms of the harmonics reduction of harmonics and finding the correct solutions.
... Note that SHE-PWM does not provide solutions for all modulation index ranges. This is a big limitation of the SHE-PWM, discussed in depth in [33]. The output voltage waveform of the CHB MLI using both MQPSO based SHE-PWM and NLC technique at m = 0.8 is depicted in Figure 7(a) and Figure 7(b) respectively whereas the harmonic spectrums are shown in Figure 8 consecutively. ...
... These findings check that the SHE-PWM control technique is superior to traditional NLCs with respect to THD. It is worth noting that SHE-PWM is usually applied to eliminating harmonics of lower order because it is the main reason why less torque is generated in the induction motors and overheat the transformer, conductors, and power lines [33]. In addition, high-order harmonics are frequently ignored, because with the help of the load impedance it can be easily removed. ...
The Multilevel Inverter (MLI) uses Selective Harmonic Elimination (SHE) of the Pulse Width Modulation (PWM) approach to tackle the fundamental harmonics with the elimination of selected lower harmonics. The optimal switching angle for this PWM method is calculated by solving a set of nonlinear equations. The PWM signal is generated using these angles in a real-time system. Modified Quantum Particle Swarm Optimization (MQPSO) is implemented in this paper to provide the optimal angle for generating the PWM signal. In this study, 5 optimal switching angles for a single-phase 11-level MLI have been calculated. It is observed that MQPSO produces optimal switching for modulation indices between 0.4 and 0.7. To obtain a quarter-wave symmetry bipolar waveform output voltage, the MQPSO based SHE-PWM has been developed and implemented by using MATLAB Simulink. The output voltage and harmonic spectrum of the proposed system are also obtained using MATLAB. Furthermore, the results are also compared with another modulation technique to validate the superiority of MQPSO based SHE-PWM. The Total Harmonic Distance (THD) has been reduced by 3.62% compared to Nearest Level Control (NLC), which has verified that the proposed method has successfully eliminated the low-order harmonics.
... To conduct this method five switching angles are determined to synthesize a staircase multilevel waveform. Selection of accurate switching angles (a i ) using Newton-Raphson iterative method are discussed in [26]. Since the symmetric HT-type module produces 5 voltage levels in a quarter wave symmetry, four harmonic components (3rd, 5th, 7th and 11th) are eliminated from the output voltage. ...
This paper introduces a new HT-type module for both symmetrical and asymmetrical multilevel inverters (MLIs) with reduced power electric components. The proposed module comprises of two back to back T-type inverters connected with four cross-connected switches. This MLI addresses two major drawbacks associated with the conventional and other recently proposed MLIs which are the high voltage stress of switches and higher power component counts. The structure of the proposed device is designed combining the beneficial features of both T-type inverter and cross-switched inverter. The 1st feature allows the module to produce negative voltage levels deprived of any extra H-bridge circuit and thus decreasing the overall voltage stress significantly. The latter feature allows the device to utilize reduced number of switches to produce higher voltage levels. A comprehensive comparative analysis is additionally established between other MLI topologies to confirm the superiority of the HT-type MLI. From this analysis, it is found that the proposed MLI has successfully overcome the issues associated with other MLIs, it was able to produce the results following industrial standards and it outperformed other MLIs in different aspects such as power components count, cost, efficiency and dynamic performance. Selective harmonic elimination pulse width modulation (SHE-PWM) and nearest level control (NLC) algorithm is considered in this manuscript to generate the output results from the proposed HT-type module. All the details about the operating principle and modulation techniques utilized for the proposed MLI module are stated and validated by both simulation and experimental results. Ó 2021 THE AUTHORS. Published by Elsevier BV on behalf of Faculty of Engineering, Ain Shams University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/ by-nc-nd/4.0/).
... The Phase Opposite Disposition Sinusoidal Pulse Width Modulation (POD-SPWM) enables the current of the different modules to be properly regulated [16]. Harmonic content can be reduced, and power factor can be corrected by using Voltage Source Inverters (VSI) [17][18][19] that can interface fuel cells and smart grids in the form of active filters in recent times [5], [20]. However, a boost stage is needed by the VSI to enable interface to the cell or electrolyser [21]. ...
... The system voltage gets high frequency harmonics injected into them once the MCSI is connected to the grid. The usual behaviour of the system is not affected by the harmonics with less than 5% THD and even after taking up to the 20 th harmonic as stated by IEEE 519 standard [19]. The harmonic spectrum of the system is shown in Fig. 8. Fig. 7(a) shows how the voltage of the grid looks like with a thorough simulation experiment. ...
This manuscript proposes a robust hydrogen-based grid system to improve the power quality of the microgrid. Advancement in hydrogen technologies such as electrolysis and fuel cell in recent times allow for more efficient and less costly conversion between electrical energy and hydrogen. Electric frameworks dependent on hydrogen energy are now being used as a replacement for big energy storages like battery. The power variations become smoother when a hydrogen-based energy system is used that has a storage of high levels of pressure as opposed to electrical systems that generate significant amount power from conventional wind or solar energies. In order to interconnect an electrolyser and fuel cell inside of a grid distribution system with low level of voltage, higher efficiency, and reliability, a bidirectional multilevel current source inverter is utilized. A simulation model of the planned structure is developed utilizing MATLAB/Simulink, showcasing the appropriate behavior under different circumstances.
... = 0.035%. Selective harmonic elimination (SHE) modulation technique can be used to completely remove the existence of the remaining harmonics (5th, 11th and 13th) from the output voltage and current [25]. It must be addressed that the estimation and eradication of harmonics is not a purpose of this manuscript. ...
This paper introduces a new hybrid topology of multilevel inverter capable of generating 21-level output voltage. The proposed topology is built using the combination of cross-switched bridge and a conventional full H-bridge. Compared to the conventional topologies and other hybrid topologies, the newly introduced multilevel inverter has the ability to maximize the number of voltage levels utilizing lower number of DC voltage sources, integrated bipolar transistor (IGBT) switches and gate drivers. A low frequency modulation technique is used to generate the ideal multilevel output voltage and gate pulses. Furthermore, the proposed topology is validated by building a hardware prototype and obtaining relevant experimental results. The acquired simulated and experimental results indicate the proper functioning of the proposed hybrid topology along with the compatibility of the applied modulation technique.
The use of multilevel inverters has gained popularity due to their ability to generate high-quality output voltage with reduced harmonic distortion. The performance of these multilevel inverters can be improved by using a low switching frequency modulation scheme as it enables precise amplitude and harmonic control in the output voltage. Determination of optimum switching angles for minimum total harmonic distortion generally requires complex algorithms with large number of iterations. This work presents a novel approach for calculating optimum switching angles at low frequencies that produces low total harmonic distortion in the output voltage. The calculation process uses only one controlling parameter that allows easy computation of optimum switching angles with a lesser number of iterations. The effectiveness of the calculated switching angles in producing lower total harmonic distortion is verified through simulation in MATLAB/Simulink platform as well as experimentally by developing a small-scale lab prototype of symmetric five-level inverter systems. For generalization, the proposed switching angle calculation technique is examined through different levels of inverter for minimum total harmonic distortions. The superiority of the proposed switching technique is verified through an extensive comparison with other popular low-frequency strategies which revealed that the proposed technique produces lower total harmonic distortions and higher fundamental voltage than those of the Equal Phase, Feed Forward, and Half Height methods. This feature of producing higher-quality fundamental voltage would make it a preferred choice for high power multi-level inverters.
This article suggests a method for diminishing the voltage unbalance in a three-phase five-level diode-clamped inverter (DCI) through the use of hexagonal hysteresis space vector modulation (HHSVM). Capacitor voltage balancing leads to enhanced system efficiency, reduced stress on components, enhanced performance, abridged electromagnetic interference, and reduced total harmonic distortion. The proposed modulation technique and its implementation are thoroughly examined in this study, along with modeling and experiment data that show how efficient the method is at lowering the capacitor voltage unbalance in the proposed five-level DCI. Capacitor voltage unbalance is reduced with the use of this HHSVM approach to 0.95%, which is a superior reduction compared to traditional PWM methods. The paper also discusses the advantages of the proposed method over other existing methods, making it a promising solution for practical applications in power electronics systems.
