H-Bridge Multilevel Research Articles

Fault Recognition and Reconfiguration for Three-Phase Five-level Cascaded H-bridge Multilevel Inverter

Fault Recognition and Reconfiguration for Three-Phase Five-level Cascaded H-bridge Multilevel Inverter

3-Phase multi-inverter with cascaded H-bridge inverter designing and implementation for renewable system

Several applications of Distributed Generation networks uses Multilevel inverters, specifically photo voltaicsystems. Few major benefits of the Multilevel inverters are its power quality and the output voltages generated from the small PV voltage sources are high.Furthermore, AC output voltage is low for these inverters and it is nearly 400 V (phase to phase voltage). This research developed a compact three-phase modular multilevel inverter with symmetrical decomposition and asymmetrical of input multi-terminal for various PV system’s ratings. The 3-phase inverter proposed uses lower number of components. The design incorporates multiple carrier PWM for reduction of THD. The PV panels are related at every 3 phase VSI (Voltage Source inverter’s) DC side. The 3-phase isolation transformer with primary open-end windings, connects 3-phase VSIs AC sides in which multilevel operation are ensured. Three half-bridge cells for each phase for 7-level output voltage generation are combined. Proposed inverter is evaluated by comparing with existing methods such as Neutral-Point-Clampedthree-phase Multi Level Inverter (NPC-MLI), Multi Level Inverter with Linear Discriminate Notation Reactor (MLI with LDNR) and Cascaded H-bridge Multi Level Inverter (CHBMLI). Hence the proposed TPM-CHI achieves 2.1 V and 2.2amps of THD under symmetric disposition, 2.2 V and 2.4amps of THD under asymmetric disposition.

THD analysis and cost comparison for an N-level H-bridge inverter incorporating passive and active filters

Multilevel H-bridge inverters have grown in popularity in electronic direct current (DC) to alternating current (AC) power conversion. In the renewable energy field, H-bridge inverters are used for converting DC voltage obtained from solar panels to AC voltage. However, H-bridge inverters produce undesirable odd harmonics in their output. Several H-bridges are, therefore, usually cascaded to reduce the total harmonic distortion (THD) in their output, but the results aren’t satisfactory in most cases. In this paper, both active and passive filters are incorporated in a cascaded H-bridge inverter to reduce the THD further. Then cost comparison is made of cascaded H-bridge inverters (3, 5, 7, 9, and 11-levels) without a filter and multilevel cascaded H-bridge inverters (3, 5, 7, 9, and 11-levels) with a passive filter or active filter. Powersim (PSIM) platform is used to perform the THD analysis.

Nine-level Cascaded H-Bridge Multilevel Inverter for Photovoltaic Sources Based on Hybrid Active Filter

Nowadays, a multilevel inverter is one of the important devices that provides a practical approach device in power system industries because of its features which are less switching losses, lower electromagnetic interference, reduced harmonic distortion, higher DC link voltages, and improved output voltage and current waveforms. Among all existed multilevel inverter, cascaded H-bridge multilevel inverter is the most attractive because of the technology development with megawatt power level. So, the cascaded H-bridge multilevel inverter has been tested and proven as a suitable DC/AC device for medium and high power applications such as renewable energy systems, electric vehicles, and motor drive applications. In this paper, the project is focusing on the combination of a nine-level cascaded H-bridge multilevel inverter connected to photovoltaic (PV) sources and a hybrid powerfilter. This project aims to study and to analyze the results of the proposed system. Thebehaviour and the performance of the designed system have shown that the system offered330V peak output AC voltage with an efficiency of 93.96% and a 5% reduction of THD.This project will be carried out only in Matlab/Simulink software.

A Generalized Scheme With Linear Power Balance and Uniform Switching Loss for Asymmetric Cascaded H-Bridge Multilevel Inverters

Under the traditional hybrid modulation strategy, the output voltage of 2:1:1 asymmetric cascaded H-bridge multilevel inverter is proved to be of high quality. However, the cascaded cells operate in unbalanced power regime and the switching loss of low-voltage cells is extremely uneven. To resolve the mentioned problems, the average power of cascaded cells is analyzed and the internal mechanism of power imbalance is revealed. Based on this, a power balance modulation strategy is proposed in this article. The modulation strategy effectively equalizes the switching loss of cells H2, H3 by modifying the triangular carriers, and then controls the conducting angle of cell H1 achieving a balanced power distribution among cascaded cells under the full modulation indexes. Compared with the existed modulation strategies, the proposed method has the merits of easy implementation, good dynamic performance, balancing low-voltage cells switching loss, and linearizing output power of cascaded cells. In addition, the modulation strategy also offers a generalized scheme, which can achieve a balanced power distribution among cascaded cells with an asymmetric ratio of i:1:1:1…. Finally, the simulation and experiment results confirm the feasibility of the modulation strategy under changes in modulation index and load.

Design of Active Fault-Tolerant Control System for Multilevel Inverters to Achieve Greater Reliability With Improved Power Quality

Modern renewable energy systems mostly utilize multilevel converter applications for improved power quality and grid synchronization purposes. A multilevel converter is an electrical device that may offer several amounts of voltage levels at the output in order to make the output more comparable to a pure sine wave. The integrity of the multilevel converter depends on the reliability of individual switches such that the converter will collapse in case of faults in these switches. In this paper, a novel 7-level Fault-Tolerant Cascaded H-Bridge Multilevel Inverter (FT-CHB-MLI) has been proposed that offers high reliability with improved power quality. A dedicated Fault Detection and Isolation (FDI) unit has been built to diagnose the faulty switch and replace it with a standby redundant switch. Total harmonic distortion and the determination of a normalized output voltage factor are employed for fault diagnosis. The Phase Disposition Pulse Width Modulation (PD-PWM) technique has been utilized for switching due to its superior performance as compared to other conventional techniques. This early fault detection method not only identified the issues but also performed preventative actions to keep the system healthy and stable. The proposed system was tested on the MATLAB / Simulink environment to verify its performance. The simulation results demonstrated that the THD has been reduced to almost 18% with a significant increase in reliability with advanced fault-tolerant architecture consisting of FDI units. The reliability analysis was carried out using Markov chains that also showed its increased reliability. A comparison of the proposed work with literature was also carried out to demonstrate its superior performance with increased reliability.

PV-Powered Grid-Tied Fault Tolerant Double-Stage DC-AC Conversion Chain Based on a Cascaded H-Bridge Multilevel Inverter

This paper is dedicated to a comprehensive study of a complete DC/AC conversion chain. Motivated by the high power demand of a variety of industrial applications, this work puts an emphasis on a double stage conversion system composed of N photovoltaic energy supplies, N DC-DC boost converters, a DC-link containing N capacitors, N H-bridge inverters connected in cascade forming the core of the structure, an LCL filter and an electrical grid. With the use of an appropriate regulator, the following control objectives are aimed to be achieved: i. the extraction of the maximum available power via the regulation of the voltage across the PV panels, ii. the fulfillment of a unitary power factor, iii. the regulation of the DC-link voltage to a desired reference. Reaching the pre-mentioned objectives requires the design of a multi-loop regulator that upgrades the features of the system under investigation to work under matching and mismatching irradiations efficiently thanks to the individual control of each PV module. As for the power factor correction (PFC) requirement and the DC link regulation, two cascaded loops are developed. The designed regulator in this study is based on the sliding mode control strategy combined with Lyapunov theory. The controlled system's performances are examined by means of simulation on Matlab/SimPowerSystems environment. The obtained results prove the effectiveness of the designed controlled system and demonstrate the fault tolerance property of the conversion chain.

An Open-Circuit Fault Detection and Localization Scheme for Cascaded H-Bridge Multilevel Converter Without Additional Sensors

In this article, a new model-based fault detection and localization scheme is proposed for cascaded H-bridge (CHB) multilevel converter to localize the open-circuit faults without needing any additional sensors. The grid current is estimated from the gird voltage, switching states, and dc bus voltages, and compared with the measured grid current. Any significant deviations in the estimated and actual grid currents of the CHB trigger an open-circuit (OC) fault. Once the fault is detected, modulation scheme is switched from phase-shifted unipolar SPWM to phase-shifted bipolar sine pulse width modulation (SPWM) to localize the OC faults. At selected time instants, the change in measured grid current for a specific period is calculated and compared with the estimated change in grid current from the system model. The abovementioned comparisons are used to localize the OC faults in the CHB. The proposed method is validated on a scale-down CHB prototype developed in the laboratory environment, and experimental results are presented to demonstrate the effectiveness of the proposed method.

Archimedes Optimization Algorithm Based Selective Harmonic Elimination in a Cascaded H-Bridge Multilevel Inverter

This paper presents the Archimedes optimization algorithm to eliminate selective harmonics in a cascaded H-bridge (CHB) multilevel inverter (MLI). The foremost objective of the selective harmonic elimination (SHE) is to eliminate lower order harmonics by finding the optimal switching angle combination which minimizes the objective function containing Total Harmonic Distortion (THD) and other specific harmonic terms. Consequently, the THD is also reduced. In this study, a recently proposed metaheuristic technique named the Archimedes optimization algorithm (AOA) is used to determine the optimal angles corresponding to the 5, 7 and 9 level CHB-MLI. AOA involves equations related to a physical law, the Archimedes Principle. It is based on the idea of a buoyant force acting upward on a body or object that is partially or completely submerged in a fluid, and the upward force is related to the weight of the fluid displaced. This optimization technique has been implemented on CHB-MLI to generate various level outputs, simulated on MATLAB™ R2021a version environment software. The simulation results reveal that AOA is a high-performance optimization technique in terms of convergence speed and exploitation-exploration balance and is well-suited to the solution of the SHE problem. Furthermore, the laboratory validated the simulation result on a hardware setup using DSP-TMS320F28379D.

Crystal Structure Algorithm (CryStAl) Based Selective Harmonic Elimination Modulation in a Cascaded H-Bridge Multilevel Inverter

This paper introduces an effective Selective Harmonic Elimination (SHE) modulation technique in a five, seven, and nine-level cascaded H-bridge (CHB) multilevel inverter (MLI). Minimization of the harmonics and device counts is the basis for the ongoing research in the area of MLI. Reduced harmonics and hence the lower Total Harmonic Distortion (THD), improve the output power quality. SHE is a low-frequency modulation scheme to achieve this goal. SHE techniques are used to eliminate the distinct lower-order harmonics by determining the optimum switching angles. These angles are evaluated by solving the non-linear transcendental equations using any optimization technique. For this purpose, the Crystal Structure Algorithm (CryStAl) has been used in this paper. It is a metaheuristic, nature-inspired, and highly efficient optimization technique. CryStAl is a simple and parameter-free algorithm that doesn’t require the determination of any internal parameter during the optimization process. It is based on the concept of crystal structure formation by joining the basis and lattice point. This natural occurrence can be realized in crystalline minerals in their symmetrically organized components: ions, atoms, and molecules. The concept has been utilized to solve non-linear transcendental equations. SIMULINK/MATLAB environment has been used for the simulation. The simulation result shows that the crystal structure algorithm is very effective and excels the other metaheuristic algorithm. Hardware results validate the performance.

Design of Self Powered Internet of Medical Things Using Robust Wolf Optimization Based PI Controller for Health Care Monitoring System

In order to gather, transmit, and develop input from the patients for monitoring their health condition through smart devices or devices which use embedded systems, such as processors and transducers and equipment for communication in the healthcare system, the Internet of Medical Things (IoMT) maintains a huge network infrastructure. These devices therefore comprise of a powerful, scalable, lightweight storage knot, which requires power and batteries to run from a practical standpoint. The above shows that the energy collection plays a significant part in the enhancement of IoMT devices’ efficiency and lifespan for its application in healthcare systems. Moreover, in view of the energy acquisition from the operational environment, energy collection is required to make the IoMT devices network more ecologically sustainable. In large solar PV generating systems, partly shading situations usually develop, causing system losses. Thus, in power-voltage curves characteristic of solar systems, the appearance of several peak levels is conceivable. These kinds of problems can be handled by using new multilayer link inverter monitoring techniques. A Maximum Point Tracking Scheme (MPPT) is being suggested for self-proposed Internet of Medical Things for the purpose of optimizing harvesting of solar power on entire PV chain with the usage of RGWO (Robust Wolf Optimization) dependent PI with PWM. The mistaken PV error might create inconsistent power supply to the 7-level H-bridge inverter linked to a grid. The modulation compensation is included in the control system in order to stabilize the grid power. The suggested technique is applied to a 7-level inverter under partial shade conditions. The multi-level modular H-bridge inverter is used for the grid-linked PV system. In addition to a DC link across all H-bridges, a short PV panel string is used for feeding each phase of n H-bridge converters which is connected in series. For pulse switching inverters, the usage of RGWO-based PI with PWM is used. The PWM is used. Then L filters used to reduce the switch harmonics found in the grid are used to link the Cascade multilevel inverter with the grid. A seven-level threephase inverter with three H-bridges allows the individual MPPT control need. The harvester is under direct sunlight and sometimes overcast circumstances realistically tested outside. The wearable IoMT sensor node uses a mean power of 20, 23 mW in a wake-up mode for one hour, and the node’s service life is 28 hours. The performance analysis is finally performed and MATLAB/SIMULINK simulation is performed.

Harmonic Profile Enhancement of Grid Connected Fuel Cell through Cascaded H-Bridge Multi-Level Inverter and Improved Squirrel Search Optimization Technique

The generation of energy by conventional systems leads to several environmental issues. Fuel Cell (FC), being a new renewable energy source, has emerged as one of the promising alternatives to obtain clean and efficient energy generation. This paper highlights the power quality enhancement of the grid connected FC through a boost converter and 25 level Cascaded H-Bridge (CHB) Multi-Level Inverter (MLI) using the classical PID controller. To drive the MLI connected to the grid for governing the Point of Common Coupling (PCC) voltage between the FC and the grid, two PID controllers have been utilized. The conventional evolutionary techniques such as Particle Swarm Optimization (PSO) and Squirrel Search Algorithm (SSA) are implemented to tune the PID controllers for dynamic operations. To further enhance the convergence speed of computation and precision of the classical techniques used, an Improved Squirrel Search Algorithm (ISSA) has been proposed in this work. The grid connected power network considered for study here is designed using MATLAB/Simulink environment. Moreover, the system is led to various rigorous voltage sag and swell conditions to test the effectiveness of the proposed controller. A detailed comparison between the conventional PID, PSO, SSA, and proposed ISSA techniques in voltage profile improvement, power quality enhancement, and reduced execution time has been featured. The results obtained highlight the proposed technique’s superiority over the classical methods in terms of improved dynamic voltage response, enhanced power quality, and reduced harmonics. The power quality indices are found out using Total Harmonic Distortion (THD) analysis. The values found out are well within the IEEE-547 indices for the proposed controller, thus justifying its real-time implementation.

Improved Cascaded H-Bridge Multilevel Inverters with Voltage-Boosting Capability

This paper proposes two improved cascaded H-bridge (ICHB) multilevel inverters that feature voltage-boosting capability. The conventional H-bridge with a front-end dc–dc boost converter was restructured for single-stage operation. The developed three-level topology not only saves one power switch but also exhibits lower voltage stress across its capacitor. Extension to five-level generation was also introduced by merely adding two power switches and one capacitor. The final five-level topology outperforms the classical cascaded H-bridge (CHB) multilevel inverter with a significant reduction in the power switch count, with a 42% and 50% reduction in both the isolated dc source and inductor counts. The power efficiency was also improved without compromising the modularity feature of the classical CHB multilevel inverter. The operation and theoretical analysis of the proposed topologies were validated via simulations and experimental tests.

Artificial Jellyfish Search Algorithm-Based Selective Harmonic Elimination in a Cascaded H-Bridge Multilevel Inverter

This paper used an artificial jellyfish search (AJFS) optimizer suitable for selective harmonic elimination-based modulation for multilevel inverter (MLI) voltage control application. The main objective was to remove the undesired lower-order harmonics in the output voltage waveform of an MLI. This algorithm was motivated by the behavior of jellyfish in the ocean. Jellyfish have the ability to find the global best position where a large quantity of nutritious food is available. The paper applied AJFS algorithm on five, seven, and nine levels of CHB-MLI. The optimum switching angle was calculated for the entire modulation range for the desired lower-order harmonics elimination. The problem formulated to achieve the objective was solved in a MATLAB environment. The total harmonic distortion (THD) values of five-, seven-, and nine-level inverters for various modulation indexes were computed using AJFS and compared with the powerful differential evolution (DE) algorithm. The comparison of THD results clearly demonstrated superior THD in the output of CHB-MLI of the AJFS algorithm over DE and GA algorithm for low and medium values of modulation index. The experimental results further validated the better performance of the AJFS algorithm.

FCS-MPC Without Steady-State Error Applied to a Grid-Connected Cascaded H-Bridge Multilevel Inverter

Cascaded H-bridge multilevel (CHB-ML) inverters are an attractive alternative for supplying power to ac grids as they have high reliability and offer an acceptable quality of voltage at their output terminals. In order to achieve efficient operation in these CHB-ML inverters, they must work at low switching frequencies. The finite-control set model predictive control (FCS-MPC) scheme is a very intuitive strategy for controlling this type of converter, but traditional FCS-MPC algorithms generally have a steady-state error when operating at low sampling frequencies and/or if there are parameters mismatch in the prediction model, regarding those of the real system. In this article, a grid-connected CHB-ML inverter that uses an improved FCS-MPC scheme is proposed. The proposed strategy eliminates the steady-state error in an MPC operating at low sampling frequencies and maintains correct operation when a change in the control reference occurs. Experimental results from a grid-connected CHB-ML inverter with three units (seven levels) demonstrate the feasibility of the proposal.

A Fast Diagnosis Scheme for Multiple Switch Faults in Cascaded H-Bridge Multilevel Converters

The increasing importance of cascaded H-bridge multilevel converters (CHBMCs) in high-power applications requires a higher priority to detect and protect against fault conditions. In this article, a current residual-based diagnosis scheme is proposed for the CHBMCs without additional sensors. On the premise of filtering the sampled dc voltages, comparing the calculated actual values of output current with the expected values in the control system, normalized diagnostic variables are established to localize single or multiple open-circuit switches. Benefit from the diagnostic variables corresponding directly to the switches of each H-bridge, this method can be easily extended to the CHBMCs with arbitrary submodules. Furthermore, the parameter estimation and enhanced detection algorithm are introduced to ensure the immunity of the diagnostic method to the large parameter changes and measurement noises. The faulty component can be accurately diagnosed within one line cycle regardless of the faulty modules and operating conditions. The effectiveness of the proposed method is substantiated using experimental results from the hardware platform of the CHBMCs.

A 129-level Asymmetrical Cascaded H-Bridge Multilevel Inverter with Reduced Switches and Low THD

Abstract: The multilevel inverter is a power conversion device which is uses multiple dc sources to provide required alternating current level. It is can be used for medium to high power applications. This paper presents a 129 level asymmetrical cascaded Hbridge multilevel inverter with reduced switching components and higher THD. The proposed inverter uses multiple dc sources with voltage ratio 1:1:2:4:8:16:32. The proposed inverter uses voltage reference technique to control the switching components of the topology. The comparative analysis of 129 level ASCHBMLI and conventional inverter topologies have been presented. The main advantages of the proposed topology is lower switching components, lower losses, and lower THD without the need of filter. MATLAB/SIMULINK software is used to perform simulation and analyse the performance of the proposed topology. Keywords: Multilevel Inverter (MLI), Asymmetrical Cascaded H Bridge Multilevel Inverter (ASCHBMLI), Cascaded H Bridge (CHB), MATLAB, Total Harmonic Distortion (THD).

Design and Implementation of Hybrid Asymmetric 15-Level Cascaded Modified H-Bridge Multilevel Inverter(CMHB-MLI) to reduce the Total Harmonics Distortion

This new cascaded modified H-bridge asymmetrical multilevel inverter (CMHB-MLI) module proposes a 15 levels with three unequal dc sources and 10 switches. The design approaches with preferable advantage with greater quality comparatively to similar modules with minimum number of semiconductor switches utilizing lower switching frequency and less dc sources. Opposite phase disposition pulse width modulation (OPD-PWM) switching technique is utilized for controlling the Semiconductor switches in CMHB-MLI. In asymmetrical topology the input source are designed with unequal magnitude is done deliberately with binary nature of voltages such as 10Vdc, 20Vdc and 40Vdc. In asymmetrical designing of MLI produces a number of different output levels with the similar number of power semiconductor switches. The results are designed using MATLAB and hardware implementation validates improved quality performance with lower total harmonicsdistortion without utilizing any filtering circuit in the output with reduced switching stress.

A Comparative Analysis of Cascaded H-Bridge Multilevel Inverters and Envisaged Topologies

Multilevel inverter circuits are widely used in the field of power generation, power quality devices, energy transmission, etc. Existing MLI have some limitations like a higher percentage of THD and reduced voltage magnitude. In this paper, two different topologies of the cascaded H-bridge MLI are discussed. The first topology uses a single DC voltage source that is shared by all MLI bridges, providing better output results. This topology is the combination of H-bridges connected in parallel at the source side, reducing the voltage sources required. The second topology, on the other hand, does have fewer switches and uses capacitors as a secondary source instead of voltage sources. H-bridges connected in this type of MLI are in series. Such two topologies are designed and simulated in MATLAB simulation software and compared as well. The said article presents a comparison within each topology based on its input DC voltage, percentage THD, Vrms, number of switches, as well as H-bridge prerequisite, among other factors.

Implementation of 7-Level and 31-Level Cascaded H-Bridge Multilevel Inverters with Reduced Number of Semiconductor Switches

Multilevel inverters are widely used because of its increased power rating with reduced harmonics and electromagnetic interference. The proposed 7-level cascaded H-Bridge inverter is symmetrical in nature and uses equal sources of DC voltage. Whereas 31-level cascaded H-Bridge inverter is asymmetrical in nature and uses unequal sources of DC voltage. The PD-PWM modulation technique was used here to achieve switching sequence. The proposed idea was validated through simulation and the results provide better efficiency, fewer low order harmonics and lower switching losses. The proposed topology is simulated using MATLAB / SIMULINK.