Non-equal DC Sources Research Articles

Notice of Violation of IEEE Publication Principles: A Hybrid ANFIS/ABC-based Online Selective Harmonic Elimination Switching Pattern for Cascaded Multi-level Inverters of Microgrids

Notice of Violation of IEEE Publication Principles A Hybrid ANFIS/ABC-based Online Selective Harmonic Elimination Switching Pattern for Cascaded Multi-level Inverters of Microgrids, by H. R. Baghaee; M. Mirsalim; G. B. Gharehpetian; H. A. Talebi; A. Niknam-Kumle, in the IEEE Transactions on Industrial Electronics After careful and considered review of the content and authorship of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE’s Publication Principles. This authorship of this paper was revised without providing attribution to, or permission from, the coauthors of an earlier version of the manuscript. Alireza Niknam-Kumle was responsible for removing the original coauthor names and replacing them with new coauthors, and then resubmitting the content in a new manuscript to IEEE Transactions on Industrial Electronics Due to the nature of this violation, reasonable effort should be made to remove all past and future references to this paper. Control of electronically-coupled distributed energy resources and topology/switching strategy of power converters have the essential roles to provide high quality power for microgrids including unbalanced and nonlinear loads. Multi-level inverters (MLIs) are used to act as high quality converters with more conversion efficiency, and less switching-frequency/switching-losses. Nevertheless their nonlinearity, complexity, and solvability features of selective harmonic elimination strategy that has affected its industrial applications, it can provide desirable output waveform by keeping fundamental component in its desired value as well as eliminating/minimizing of low-order harmonics. This paper presents adaptive neuro-fuzzy inference system (ANFIS) as a switching angle estimator for harmonic optimization problem in cascade MLIs, which is trained based on the database including optimal switching angles obtained for inverter with non-equal DC sources by artificial bee colony (ABC) algorithm. The reliable search ability, accuracy and convergence time of ABC have been compared with particle swarm optimization algorithm. Also, performance of ANFIS is compared with artificial neural network based on correlation coefficient and root mean square error. Simulation results, experimental tests and real-time simulations reveals the effectiveness of proposed estimator for online elimination of low-order harmonics of MLIs in microgrids and its superiority over other methods.

Reduced Device Count for Self Balancing Switched-Capacitor Multilevel Inverter Integration with Renewable Energy Source

In this study, a new switched-capacitor-based seven-level inverter topology with a photovoltaic system is presented. The proposed topology requires a smaller number of devices and has the ability to self-balance the voltage across the capacitor. The proposed topology configuration is simple and has the ability to extend to higher levels of voltage. This multilevel inverter topology is suitable for low- and medium-voltage applications with photovoltaic (PV) system integration. To improve the PV system efficiency as an input of a DC–DC boost converter, a Fuzzy logic-based maximum power point controller technique is used. A PV system with a DC–DC boost converter integrates with the proposed seven-level inverter topology. The anti-predatory particle swarm optimization (APSO) technique is used to solve the non-linear transduction equations of the seven-level PV switched-capacitor-based multilevel inverter (7L−PV−SCMLI) topology. The proposed APSO is described to minimize the harmonics in the multilevel inverter (MLIs), which is a complex optimization problem involving a non-linear transcendental equation. Furthermore, APSO can be applied in order to solve non-linear transcendental equations for all symmetrical and asymmetrical MLIs that have equal and non-equal DC sources. The APSO-based selected harmonic elimination (SHE) technique obtained the best switching angle value, and the optimized obtained switching angles reduced the total harmonic distortion (THD) of 7L−PV−SCMLI.

On PWM Strategies and Current THD for Single- and Three-Phase Cascade H-Bridge Inverters with Non-Equal DC Sources

Cascade H-bridge (CHB) inverter is an attractive choice for integration of DC sources of different nature, e.g., for distributed generation with energy storage, photovoltaic generation, etc. In general, non-equal DC voltage sources can affect the total harmonic distortion (THD) of the CHB by introducing undesirable low-frequency subharmonics. This paper investigates different level-shifted (LS) and phase-shifted (PS) pulse width modulation (PWM) strategies for single- and three-phase cascade H-bridge inverters with non-equal DC sources from the load current THD minimization perspective. The best current quality is provided by LS PWM, as reported in the literature. The paper provides a simple time domain explanation of LS PWM superiority. However, PS PWM may be a preferable choice for practical applications due to fair power and loss sharing across individual H-bridges. The paper explains how to obtain the best current quality by PS PWM carriers’ order arrangement (DC sources switching sequence selection).

Design of PSO Based Cascaded Multilevel Inverter with Unequal DC Sources

This paper focusing on, the total harmonics distortion (THD) of the output voltage is minimized by the help of a cascade multilevel inverter with non-equal DC sources using particle swarm optimization (PSO) algorithm. The nonlinear transcendental equation that describing the harmonic elimination problem is solved by using many methods existing in literature. In the proposed technique, unequal DC sources are taken for the multilevel inverter, which is practical when different renewable sources are used. The desired switching angles are found out by implementing PSO algorithm which results the minimum THD. Experimental details along with simulation results of 11-level inverter are shown to validate the theory.

Selective harmonic elimination in multilevel inverter using hybrid APSO algorithm

This study presents selective harmonic elimination pulse width modulation technique-based hybrid asynchronous PSO-Newton-Raphson (APSO-NR) algorithm for the elimination of undesired harmonics in cascaded H-bridge multilevel inverter. The proposed algorithm is applicable to all levels of MLI having equal and non-equal DC sources. In the proposed method, ring topology-based APSO algorithm is hybrid with NR method. APSO worked as a global search technique and NR is used for the refinement of best solutions. APSO-NR is applied to the seven-level inverter to eliminate fifth and seventh harmonics. In simulations, the performance of the proposed algorithm is compared with genetic algorithm, bee algorithm and particle swarm optimisation. The results proved that the proposed algorithm is efficient, and gives more precise firing angles in less number of iterations with high capability of tackling local optima. For the 48% of modulation index range, APSO-NR minimised the fitness function value lower than (10 -25 ). The proposed algorithm is validated through the experimental implementation of the three-phase seven-level inverter.

Harmonic elimination of a photo-voltaic based cascaded H-bridge multilevel inverter using PSO (particle swarm optimization) for induction motor drive

The present paper proposes a novel method to eliminate harmonics in a solar powered CHMLI (cascaded H-bridge multilevel inverter). The problem uses Newton Raphson and PSO (Particle Swarm Optimization) based SHE (Selective Harmonic Elimination) techniques for solving the non-linear transcendental equations and to obtain the optimal switching angles. The optimized switching angles obtained offline are utilized to minimize the THD (Total Harmonic Distortion). The major concern in the harmonic-elimination problem in the non-equal dc sources system is the solution of the nonlinear transcendental equations. However, the proposed method can solve this problem in a simpler manner, by just converting non-equal dc sources into equal dc source using the ANFIS (Adaptive Neuro Fuzzy Inference System)/Constant Voltage Maximum Power Point Tracker algorithm for the Photo-voltaic system. The performance are evaluated using simulation results for PV fed 11-level cascade H-bridge inverter with induction motor drive. The simulation results are validated using an experimental model of CHMLI with Xilinx Spartan®-3A DSP FPGA based controller.

Differential Evolution based SHEPWM for Seven-Level Inverter with Non-Equal DC Sources

This paper presents the application of differential evolution algorithm to obtain optimal switching angles for a single-phase seven-level to improve AC voltage quality. The proposed inverter in this article is composed of two H-bridge cells with non-equal DC voltage sources in order to generate multiple voltage levels. Selective harmonic elimination pulse width modulation (SHPWM) strategy is used to improve the AC output voltage waveform generated by the proposed inverter. The differential evolution (DE) optimization algorithm is used to solve non-linear transcendental equations necessary for the (SHPWM). Computational results obtained from computer simulations presented a good agreement with the theoretical predictions. A laboratory prototype based on STM32F407 microcontroller was built in order to validate the simulation results. The experimental results show the effectiveness of the proposed modulation method.

Harmonics Elimination in a Multilevel Inverter with Unequal DC Sources Using a Genetic Algorithm

In this paper, an optimal solution to the harmonic reduction problem in a cascaded multilevel inverter with non-equal DC sources using a genetic algorithm (GA) is presented. Switching angles are generated for different values of modulation index by the proposed algorithm, considering minimum voltage total harmonic distortion (THD) whereas selected harmonics are controlled within the allowable limits at all desired modulation indices including the point of discontinuity. Results are stored as a look-up table to be used to control the inverter for a certain operating point. The computed angles are used in a simulated circuit in Matlab\Simulink to validate the results.

Harmonic Elimination of Cascade Multilevel Inverters with Nonequal DC Sources Using Particle Swarm Optimization

In this paper, the elimination of harmonics in a cascade multilevel inverter by considering the nonequality of separated dc sources by using particle swarm optimization is presented. Solving a nonlinear transcendental equation set describing the harmonic-elimination problem with nonequal dc sources reaches the limitation of contemporary computer algebra software tools using the resultant method. The proposed approach in this paper can be applied to solve the problem in a simpler manner, even when the number of switching angles is increased and the determination of these angles using the resultant theory approach is not possible. Theoretical results are verified by experiments and simulations for an 11-level H-bridge inverter. Results show that the proposed method does effectively eliminate a great number of specific harmonics, and the output voltage is resulted in low total harmonic distortion.

Elimination of harmonics in multilevel inverters with non-equal dc sources using PSO

Multilevel inverters supplied from equal and constant dc sources almost do not exist in practical applications. The variation of the dc sources affects the values of the switching angles required for each specific harmonic profile, as well as increases the difficulty of the harmonic elimination’s equations. This paper presents an extremely fast optimal solution of harmonic elimination of multilevel inverters with non-equal dc sources using a novel Particle Swarm Optimization (PSO) algorithm. The overall system is suitable for large variable speed drives, UPS systems, and on-line utility applications such as static var compensation. A set of mathematical equations describing the general output waveform of the multilevel inverter with non-equal dc sources is formulated. PSO is then employed to compute the optimal solution set of switching angles, if it exists, for each required harmonic profile. Theoretical studies for different case studies regarding the number of levels and harmonic profile are carried out to show the effectiveness and robustness of the proposed technique, and validated through both simulations and laboratory experimentation.

Selective Harmonic Elimination PWM Control for Cascaded Multilevel Voltage Source Converters: A Generalized Formula

This paper proposes a generalized formulation for selective harmonic elimination pulse-width modulation (SHE-PWM) control suitable for high-voltage high-power cascaded multilevel voltage source converters (VSC) with both equal and nonequal dc sources used in constant frequency utility applications. This formulation offers more degrees of freedom for specifying the cost function without any physical changes to the converter circuit, as compared to conventional stepped waveform technique, and hence the performance of the converter is greatly enhanced. The paper utilizes the merits of the hybrid real coded genetic algorithm (HRCGA) in finding the optimal solution to the nonlinear equation system with fast and guaranteed convergence. It is confirmed that multiple independent sets of solutions exist. Different operating points for both five- and seven-level converters including single- and three-phase patterns are documented. Selected experimental results are reported to verify and validate the theoretical and simulation findings.

Elimination of Harmonics in a Multilevel Converter With Nonequal DC Sources

Eliminating harmonics in a multilevel converter in which the separate dc sources vary is considered. That is, given a desired fundamental output voltage, the problem is to find the switching times (angles) that produce the fundamental while not generating specifically chosen harmonics. Assuming that the separate dc sources can be measured, a procedure is given to find all sets of switching angles for which the fundamental is produced while lower order harmonics are eliminated. This is done by first converting the transcendental equations that specify the elimination of the harmonics into an equivalent set of polynomial equations. Then, using the mathematical theory of resultants, all solutions to this equivalent problem can be found. Experimental results are presented to validate the theory.