Cascaded Multilevel Inverter Research Articles

A 5LCHB Inverter for PV Transformerless Applications With Reduced Leakage Ground Current

The transformerless inverters for photovoltaic systems are widely used as it features low cost, volume, and weight. Thus, in recent years, its study has been of great interest to the research community. In this paper a transformerless cascade multilevel inverter for photovoltaic applications with leakage ground current compensation capability is presented. The proposed solution involves a second-order LC output filter with a particular connection, which is referred to as the DC-link-tied LC output filter. This solution is aimed to deal with the leakage-ground current issue, regardless of the considered PWM strategy. The mathematical model of the system involving such a particular LC output passive filter configuration is presented, out of which, both the differential-mode and the common-mode models are obtained. These models are used to explain the leakage-ground current improvement of the proposed DC-link-tied LC output filter. This hardware solution is evaluated under different modulation schemes to contrast the converter output response and the leakage-ground current performance. Finally, simulation and experimental results are performed using a 1 kW academic prototype to assess the performance of the proposed DC-link-tied LC output filter used in a transformerless inverter application.

Fuzzy and ANFIS Controllers to Improve the Power Quality of Grid Connected PV System with Cascaded Multilevel Inverter

In this paper, A Cascaded Multi level Inverter (CMLI) interconnected with the 10 KW PV System, Boost Converter along with Cascaded Feed Forwarded Neural Network (CFFNN) MPPT Controller is proposed to improve the Power Quality (PQ) for Linear, Non-linear and unbalanced loading conditions and minimize the total Harmonic Distortion (THD). The CMLI Consists of Novel type 9-Level Inverter with Reduced number of switches, and is connected to Bridged type inverter as cascaded, to get the required amount of Output voltage which can be used for grid integration. For controlling the inverter the Current controller is much required to control the current and to synchronize the Phase lock loop (PLL) is important. Here a new Adoptive Neuro Fuzzy Interface System (ANFIS) Control tuned with PI Controller is used to advance the performance of the power quality of the system under various loading conditions and undesired oscillations and THD can be improved compared with Conventional PI Controller and Fuzzy-PI Controller, Load voltage and current waveforms are analyzed under IEEE 519. The system is developed in the MATLAB environment to check the dynamic PV performance with MPPT controller and the results are found satisfactory.

ПРИНЦИПИ УДОСКОНАЛЕННЯ БАГАТОРІВНЕВИХ АВТОНОМНИХ ІНВЕРТОРІВ НАПРУГИ

The article considers the properties of the most commonly used two-and multilevel inverter topologies used in systems for converting electricity from several primary power sources into the required high-quality output voltage for low-voltage networks and high-voltage consumers. However, a common disadvantage of most known multilevel converters is the increasing complexity of power structures, an increase in the number of primary power sources, power elements, and the cost of devices as the number of their voltage levels increases. Two schemes of alternative three-level autonomous voltage inverters with a high-frequency autotransformer with a midpoint and an example of constructing their digital control system are proposed. The analysis of their work on PSpice models in the OrCAD design system is carried out. The possibility of obtaining six voltage sublevels with fewer power elements and increased output voltage quality is shown, compared to the corresponding cascade multilevel inverters. The advantages and applications of autotransformer bridge voltage inverters in terms of energy and functionality compared to well-known multilevel inverters are presented. Ref. 8, fig. 7.

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.

Transformer Based Cascaded Multilevel Inverter with Reduced Number of Switches

Abstract: This project presents the simulation of “transformer based cascaded multilevel inverter with reduced number of switches” with R-load and. It has the advantages of reduced number of switches and dc sources compared to conventional configurations and consequently higher efficiency. The simulation is accomplished for one stage (3-level), two stage (5-level, 7- level, 9-level), three stage (7-level, 11-level, 15-level, 19-level, 27-level) and four stage (29-level, 31-level, 33-level, 35-level). And their performance is analysed in terms of THD (Total Harmonic Distortion) for output voltages and currents. The FFT (Fast Fourier Transform) analysis is used in order to evaluate the harmonic distortion. The simulation is carried out by using MATLAB/SIMULINK software. Index Terms: cascaded asymmetric multilevel inverter, transformer-based cascaded multilevel inverter, balance of power distribution.

Optimization of a New Extended Cascaded Multilevel Inverter Topology to Reduce DC Voltage Sources and Power Electronic Components

This work proposes a new multilevel inverter consisting of basic and submultilevel units. The basic unit is made-up of four isolated dc voltage sources, two bidirectional switches and ten unidirectional switches. To increase the number of the output voltage levels, a cascaded architecture based on series connection of sub-multilevel is proposed. The proposed inverter utilizes two algorithms to determine the values of dc voltage sources. Number of IGBTs, dc voltage sources, gate driver circuits, variety of dc voltage sources and peak standing voltage on the switches are calculated and their optimization to produce maximum number of levels in output voltage is investigated. To examine advantages of the proposed inverter, the topology is compared with other topologies. The results show superiority of proposed topology over most conventional topologies, in number of circuit components. Finally, to confirm the performance of the proposed multilevel inverter, experimental results of a 25-level inverter prototype are provided.

Single input qZ‐source cascaded multilevel inverters : Analysis , design, and implementation

The Single Input quasi-Z-Source Cascade Multilevel Inverter (SIqZS-CMI) has the ability to make use of a single DC input source and to share active power among all cascaded qZS modules. This unique feature, do not present in any other quasi-Z-Source (qZS) multilevel inverter in the literature, is accomplished by replacing one of its Z-impedance inductances by a coupled inductor. With this topology, it is possible to make use of a single low voltage PV string, favoring the use of small size residential rooftop systems. In addition, it simplifies the system grounding and the compliance with many Installation, Maintenance, and Safety Codes and Standards. The proposed control strategy enables high quality current injection into the grid, keeping the DC bus voltage regulation, ensuring precise power balancing with symmetric multilevel waveforms. Experimental results from a 5-level SIqZS-CMI prototype demonstrate the system's performance and its advantages.

An Advanced PWM Technique for MMC Inverter Based Grid-Connected Photovoltaic Systems

Recent developments in multilevel inverters have provided impetus for their applications in the medium voltage renewable energy generation processes. This paper proposes an advanced pulse width modulation technique for a modular multilevel cascaded (MMC) inverter based grid integrated solar photovoltaic (PV) system. It offers lower total harmonic distortion (THD) and power losses compared to the existing modulation techniques. This paper shows the design and performance evaluation of the proposed technique using a 3-phase 5-level MMC inverter-based grid connected PV system. The proposed PWM technique offers 12.49% (without filter) and 0.96% (with filter) output line voltage THDs. It also offers 4.64% output current THD, which complies with the IEEE-519 standard for grid integration. Besides THD reduction, it also reduces the switching and conduction power losses of the MMC inverter. Lower losses may help to keep device temperature low, which is essential for power converters used in superconducting magnetic energy storage (SMES) systems. The simulation is performed in MATLAB/Simulink and the proposed technique is experimentally validated with a laboratory test platform.

Harmonic Suppression Scheme for Multipulse Converter Fed Multilevel Inverter-Based IM Drive

The medium-voltage induction motor drives are regularly utilized for crucial application in enormous industries. It is difficult to design a highly efficient drive system with a satisfactory power quality standard not only at the drive end but also at the grid end. To breakthrough this issue, a 36-pulse ac–dc converter fed seven-level binary cascaded H-bridge multilevel inverter (CHB-MLI) based drive system is presented in this work, where a 36-pulse converter is employed to enhance the power quality at the grid end. For this, the phase-shifted technique is implemented on a multiwinding transformer to eliminate the harmonics injected by the nonlinear diode bridge rectifier toward the grid side. Apart from this, the genetic algorithm selective harmonic elimination (GA-SHE) is applied to a seven-level binary CHB-MLI to diminish lower order (fifth and seventh) harmonics at the drive end. Moreover, a GA is adopted to determine the optimized switching angles by the solution of the nonlinear trigonometric equation of SHE. Furthermore, the GA-SHE-based fundamental frequency modulation scheme is favorable to decrease the switching losses and to enhance the drive end converter efficiency. The performance during the dynamics and steady state of the presented drive system with the indirect field-oriented control is analyzed through simulations and experiments on 298.4 kW and 7.5 kW squirrel-cage induction motors, respectively.

Modified PWM Technique for a Multi-Pulse Converter Fed Multilevel Inverter Based IM Drive

This article presents a 36-pulse converter and five-level cascaded H-bridge multilevel inverter (CHB-MLI) fed medium voltage induction motor drive (MVIMD) system. The multiwinding transformer (MWT) for a 36-pulse ac–dc converter is designed in such a way that it requires the least number of windings and enhances power quality at the grid end. This is helpful to reduce the size, weight, and cost of the presented MVIMD. The modified carrier level shifted pulsewidth modulation (MC-LSPWM) is used to control five-level CHB-MLI fed induction motor, which adheres the power quality standard IEEE519 at drive end. The main characteristic of used PWM is that it has inherent rotating switching pattern nature, which is helpful to enhance the power quality performance and to decrease the continuous conduction time of the H-bridge. Whereas, this continuous conduction among H-bridges, is not balanced in the level-shifted pulsewidth modulation (LSPWM). Therefore, conduction losses among the H-bridges of CHB-MLI are balanced and reduced by this MC-LSPWM for continuous operation, which is not possible with the conventional LSPWM. The practicality of this MVIMD with an indirect field-oriented control and MC-LSPWM technique, is substantiated via a comparison with the configuration reported in the literature, simulation, and experimentation, respectively. Performance of the drive system is evaluated during different operating conditions, such as starting, steady-state, speed and load perturbations. Further, a detailed comparative analysis of results is presented, which demonstrates that presented MWT configuration has fewer number of windings (only thirty-three windings), less conductor material and minimum losses. Thus, the presented configuration of MVIMD shows excellent performance characteristics with reduced size and weight such as currents total harmonic distortion is 2.5% (grid end), 3.66% (drive end) and efficiency of the drive is 88.101%, when the drive runs at rated conditions.

Design and Implementation of Asymmetric Cascaded Multilevel Inverter with Optimal Components

A novel asymmetrical cascaded one-twenty-five level multilevel inverter is proposed with optimal components. The proposed inverter consists of three sub-cells connected asymmetrical configuration to generate a 125-level output voltage. The sub-cell comprises six power switches and two DC sources to produce five output voltage levels with symmetrical configuration. This paper presents the five, twenty-five, one-twenty five-level inverters with optimal components with very lower harmonics. The results of the proposed inverters are experimentally tested with linear and non-linear loads. During dynamic circumstances, the suggested inverters are extremely stable. The proposed inverters will generate a greater voltage level with nominal harmonics as per IEEE standards. A complete comparison is made with previously published similar MLIs with proposed twenty-five MLI. The Proposed MLI has several merits such as cost factor, optimal components, THD, and TSV. The proposed five, twenty-five, and one-twenty-five level inverters are experimentally implemented with the help of the dSPACE RTI1104 controller. The proposed inverters are well suited for grid-connected and renewable applications.

A Genetic-Based Hybrid Algorithm Harmonic Minimization Method for Cascaded Multilevel Inverters with ANFIS Implementation

Selective harmonic elimination pulse-width modulation (SHEPWM) is a widely adopted method to eliminate harmonics in multilevel inverters, yet solving harmonic amplitude equations is both time consuming and not accurate. This method is applied here for a 7-level cascaded multilevel inverter (CMLI) with erroneous DC sources. To meet the seven harmonic amplitude equations, two notches are applied with the use of higher switching frequency than nominal. These notches can be placed in six different positions in the voltage wave, and each was assessed in a separate manner. In order to solve the equations, a hybrid algorithm composed of genetic algorithm (GA) and Newton–Raphson (N-R) algorithm is applied to achieve faster convergence and maintain the accuracy of stochastic methods. At each step of the modulation index (M), different positions for the notches are compared based on the distortion factor (DF2%) benchmark, and the position with lowest DF2% is selected to train an artificial neural fuzzy interface system (ANFIS). ANFIS will receive the DC sources’ voltages together with required M and will produce one output; thus, eight ANFISs are applied to produce seven firing angles, and the remaining one is to determine which one of the notches’ positions should be used. Software simulations and experimental results confirm the validity of this proposed method. The proposed method achieves THD 8.45% when M is equal to 0.8 and is capable of effectively eliminating all harmonics up to the 19th order.

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.

Optimization and Implementation of a New Topology for Cascaded Multilevel Inverters with Reduced Number of Semiconductor Devices

Optimization and Implementation of a New Topology for Cascaded Multilevel Inverters with Reduced Number of Semiconductor Devices

Switched Capacitor Based Cascaded Half-Bridge Multilevel Inverter With Voltage Boosting Feature

Cascaded multilevel inverter (CMI) topology is prevalent in many applications. However, the CMI requires many switches and isolated dc sources, which is the main drawback of this type of inverter. As a result, the volume, cost and complexity of the CMI topology are increased and the efficiency is deteriorated. This paper thus proposes a switched-capacitor-based multilevel inverter topology with half-bridge cells and only one dc source. Compared to the conventional CMI, the proposed inverter uses almost half the number of switches, while maintaining a boosting capability. Additionally, the main drawback of switched-capacitor multilevel inverters is the capacitor inrush current. This problem is also averted in the proposed topology by using a charging inductor or quasi-resonant capacitor charging with a front-end boost converter. Simulation results and lab-scale experimental verifications are provided to validate the feasibility and viability of the proposed inverter topology.

Reconfiguration Strategy for Fault Tolerance in a Cascaded Multilevel Inverter Using a Z-Source Converter

The cascade multilevel inverters are widely used in industrial manufacturing processes for DC-AC conversion. Therefore, the reliability and efficiency improvement, optimized control, and fault-tolerant strategies are areas of interest for researchers. The fault tolerance strategies applied to cascade multilevel inverters are classified as material redundancy and analytical redundancy. This paper presents the use of the Z-source converter as a fault reconfiguration method applied to a cascade multilevel inverter. On the one hand, the proposed approach has the characteristic of combining the use of material redundancy (modifying the output voltage by changing the Z-source operation), and on the other hand, it has the use of analytical redundancy (modifying the switching sequence of the multilevel inverter, changing from symmetrical to asymmetrical operation mode). This approach has been validated by experimental results of the system under fault-free conditions and employing the Z-source converter as the main fault reconfiguration element. The proposed fault reconfiguration strategy allows the cascaded multilevel inverter to continue to operate even in the presence of a fault by having continuous operation.

Non-conventional Cascade Multilevel Inverter with Lower Number of Switches by Using Multilevel PWM

The multilevel inverter is attracting the specialist in medium and high voltage applications, among its types, the cascade H bridge Multi-Level Inverter (MLI), commonly used for high power and high voltage applications. The main advantage of the conventional cascade (MLI) is generated a large number of output voltage levels but it demands a large number of components that produce complexity in the control circuit, and high cost. Along these lines, this paper presents a brief about the non-conventional cascade multilevel topologies that can produce a high number of output voltage levels with the least components. The non-conventional cascade (MLI) in this paper was built to reduce the number of switches, simplify the circuit configuration, uncomplicated control, and minimize the system cost. Besides, it reduces THD and increases efficiency. Two topologies of non-conventional cascade MLI three phase, the Nine level and Seventeen level are presented. The PWM technique is used to control the switches. The simulation results show a better performance for both topologies. THD, the power loss and the efficiency of the two topologies are calculated and drawn to the different values of the Modulation index (ma).

A Developed H-Bridge Cascaded Multilevel Inverter with Reduced Switch Count

Multilevel Inverter integrates several Direct Current (DC) sources to produce a single-phase Alternating Current (AC) waveform that can be used to meet the domestic and commercial power demand. This article introduces a novel Multi Source Cascaded Multilevel Inverter with a reduced number of switches for the efficient use of DC voltage sources. The conversion efficiency can be increased by the presented topology which is simple in design to overcome the significant switching losses in the power electronics devices. Optimal Firing Angle and Phase Opposition Disposition Pulse width Modulation Techniques were used to reduce the harmonics at the desired output of the inverter and also to improve the power quality of the presented topology. This article also proposes two Asymmetric Multilevel Inverter Topologies. A comparison has been made, on the number of switches required and the efficiency of the inverters to differentiate the presented Topologies from other topologies of the multilevel inverter. Finally, the performance characteristics of the presented topologies have been designed and investigated using MATLAB Simulation. Simulation results were validated using an experimental setup.

A Novel Three-Phase Transformerless Cascaded Multilevel Inverter Topology for Grid-Connected Solar PV Applications

Nowadays, multilevel inverters (MLIs) are gaining huge popularity for high power transformerless PV applications. Among the traditional MLIs, the cascaded H-bridge (CHB) MLI accommodates lower voltage rated input dc sources, which reduce the voltage stress across the devices. However, the CHB MLI requires multiple PV sources as separate dc-link voltage sources, which create more paths for leakage currents. Therefore, it is a challenging task to deal with the leakage currents in the case of CHB MLIs. In this article, a novel three-phase transformerless inverter topology for grid-connected solar PV application is introduced. This proposed that the inverter topology has six switches per phase, and it has the combined advantages of dc-bypass and ac-bypass circuit configurations. A new modulation strategy is developed for the proposed topology; it is based on a sine triangle pulsewidth modulation technique combined with the dedicated logic functions. The gate pulses for all switches are provided by using these dedicated logic functions. The switching pulses obtained from the dedicated logic functions control all the inverter switches so that the variation of common-mode voltage (CMV) is constant during the inverter operation. This results in reduced leakage current throughout the operation of the inverter. The theoretical analysis, simulations, and experimental results are presented to validate the proposed topology concept for a 3-kVA grid-connected system. Both the simulation and experimental results show that the proposed solution can well attenuate the leakage current; all the results are presented in the article.

Novel Level Shifted PWM Technique for Unequal and Equal Power Sharing in Quasi Z-Source Cascaded Multilevel Inverter for PV Systems

Conventional phase-shifted pulsewidth modulation (PS-PWM) is a usual switching technique for Z-source/quasi-Z-Source (qZS)-based cascaded multilevel inverters (CMIs) (qZS-CMIs). The PS-PWM scheme causes higher switching losses and creates an electromagnetic interference (EMI) problem for higher number of cascaded modules. To address these issues, a novel, modified level-shifted PWM (LS-PWM) technique is proposed with the aim of obtaining equal power from cascaded modules under abnormal conditions. The direct use of the alternate phase-opposed disposed PWM (APOD-PWM) results in unequal power sharing between the qZSI modules, under all operating conditions. An effective carrier rotation is incorporated in the conventional APOD-PWM to make equal power sharing between the qZSI modules. The proposed scheme is an excellent solution for photovoltaic (PV) systems to address the problem of partial or complete shading, temperature variation, PV module failure, and dust accumulation on the PV panels. Furthermore, the relationship between PS-PWM and APOD-PWM is geometrically obtained, which indicates that the proposed modulation scheme gives higher voltage gain over LS-PWM and PS-PWM techniques. In addition, detailed switching loss analysis for the proposed PWM methods is added to validate low-switching losses, and thus high efficiency. The MATLAB Simulink simulations are presented to verify the proposed modulation. An experimental prototype is developed, and the experimental outcomes validate the improved performance of the multilevel qZSI with proposed modulation.