Multilevel Inverter Research Articles

Design and implementation of novel multilevel inverter with full DC-utilization

ABSTRACT This paper presents a novel single-source transformer-based nine-level (9 L) inverter configuration. The design incorporates a three-level neutral-point-clamped (3 L NPC) inverter, a 3-L full bridge, and a transformer to produce 9 L output voltage levels. In particular, one of the 2 L legs in the full bridge is common among the transformer and the load. The proposed structure minimises the components compared to existing transformer-based nine-level inverters. Thus, the suggested inverter volume, cost, and complexity are minimised. Furthermore, a pulse width modulation method has been developed to generate the necessary gating pulses for the proposed inverter. Additionally, a complete comparison study illustrates the enhanced performance of the suggested architecture. The validity of the suggested 9 L inverter is assessed by performing MATLAB simulations and using a scaled prototype. The results obtained from the simulations and experimental tests are then presented and analysed. A clear correlation was observed between the simulation and the hardware results.

Design DC/AC Converter for Renewable Energy Sources

Multilevel inverters are vastly used in power systems and “renewable energy sources” (RES) to provide an AC voltage with a low level of harmonic contents. This paper aims to design a 9-level inverter for RES such as photovoltaic (PV), wind turbines, and fuel cells… etc. The proposed inverter is constructed by 12 IGBT switching devices where all of which are powered by 4 DC sources of 81 V without balancing capacitors to make DC voltage 324 V. A Phase disposition (PD), alternative phase opposition disposition (APOD), and POD with a slight phase shift are the methods of modulations that are used to provide a sinusoidal waveform of the output voltage and current. The minimum “Total harmonic distortion” (THD %) of the output voltage of the inverter is 13.68 % and 1.7 % in the cases where there is no filter and with filter conditions respectively. The load voltage is regulated by a PI controller based on the RMS value of the inverter output voltage.

Novel chattering free binomial hyperbolic sliding mode controller for asymmetric cascaded E-type bonded T-type multilevel inverter-based dynamic voltage restorer to meliorate FRT capability of DFIG-based wind turbine

The endurance capability of Doubly Fed Induction Generator (DFIG)-based wind turbine to network against different disturbances is an important criterion to meet the recent grid codes requirements. This generator has to provide the required energy under the perturbation conditions which is principally specified by Fault Ride-Through (FRT) capability. It refers to safe and continuous operation of DFIG without interruption which has been performed by Dynamic Voltage Restorer (DVR) using fast and accurate compensation of the voltage fluctuations. This paper aims to introduce an innovative quasi-sinusoidal voltage synthesizer for DVR to enhance the power quality and power delivery. Hence, a new Asymmetric Cascaded E-type Bonded T-type Multilevel Inverter (ACEBTMI) with binary geometric progression form of DC sources is proposed to provide high-step staircase sinusoidal voltage containing low semiconductor switches. Then, accurate triggering signals for the suggested ACEBTMI corresponding to the voltage fluctuations have been provided by new Chattering Free Binomial Hyperbolic Sliding Mode Controller (CFBHSMC). To validate compensation capability of the proposed DVR, ACEBTMI part has been compared with some traditional and familiar multilevel inverters, and also CFBHSMC part has been compared with SMC, FLC and PID controllers. In precise, the simulation results have definitely confirmed the accurate tracking and robust control performance of CFBHSMC to support ACEBTMI-based DVR which enables DFIG to ride-through different voltage perturbations.

A new method for selecting optimum levels in asymmetric Cascaded H‐Bridge‐Multilevel Inveter with variable DC sources

SummaryIn general, cascaded H‐bridge multilevel inverters (CHB‐MLI) are typically operated with either symmetrical or asymmetrical input DC sources, set at predefined specific ratios such as binary (1:2) or trinary (1:3) in the case of asymmetry, to achieve the desired output voltage waveform. However, if any DC source fails to provide the predefined voltage magnitude, or CHB‐MLIs with unspecified DC source ratios are utilized, the output voltage waveform may exhibit unequal magnitudes between consecutive levels, thereby causing a significant increase in total harmonic distortion (THD). Conventionally, to mitigate this effect, the corresponding H‐bridge is bypassed through zero voltage switching, which leads to an additional burden on the remaining H‐bridges to serve the same load. To reduce the burden on the remaining cells and improve the THD profile of the inverter, this article proposes a novel method for CHB‐MLI with varying DC magnitudes. It aims to enhance the quality of the output voltage waveform by strategically selecting optimum voltage levels rather than utilizing all available levels when CHB‐MLI has unspecified or variable DC sources. This approach can achieve a more balanced distribution of voltage magnitudes across successive levels by eliminating redundant states. Moreover, the proposed technique can reduce switch losses and enhance the converter's efficiency. The proposed method is validated through MATLAB/Simulink software simulations, followed by experimental verification.

A 17-level octuple boost switched-capacitor inverter with lower voltage stress on devices

This paper presents a new structure for switched-capacitor multilevel inverter with octuple voltage gain capability. The proposed inverter utilizes three capacitors, 13 semiconductor switches, three diodes, and an input voltage source to achieve a 17-level output voltage. The switched capacitors naturally achieve voltage balancing without the need for sensors or additional circuits, indicating the ease of control of the proposed structure. To control the inrush current of the switched capacitors, a charge limiting inductor has been utilized in the charging path of the capacitors. This not only reduces the inrush current of the capacitors and the input source current but also enables faster capacitor charging and extends their lifetime. The switches used in the proposed structure can withstand a maximum of 4 times the input voltage value or the half of the maximum output voltage, which is a significant advantage for the proposed structure. A detailed comparison with similar structures is provided to examine the advantages and disadvantages of the suggested inverter. The procedure of self-voltage balancing of the capacitors and the functional modes of the proposed topology has been explained in detail. The proposed structure is suitable for applications such as renewable energy sources transfer to load or grid. The performance of the proposed topology under different conditions is confirmed through simulation in the Matlab\\Simulink software and the implementation of the laboratory sample.

RSO based selective harmonic elimination control for nine-level switched capacitor inverter

Abstract Renewable energy utilization has gained much attention in the recent time owing to the sharp increase in the power demand. Out of different renewable sources, photovoltaic (PV) energy utilization in different forms is one of key focus. Power converter such as multilevel inverters (MLIs) are proven as key components for PV systems as well as for other applications such as motor drives, electric vehicles, and charging stations. With the advancement of the design of MLIs, the switched-capacitor (SC) based MLIs have been widely deployed for their boosting capability which is a major requirement for PV systems. In this paper, a reduced switch single input step-up 9-level SC MLI is first proposed. Followed by this, a new Rat Swarm Optimization (RSO) based Selective Harmonic Elimination (SHE) control method is incorporated for switching operation. RSO has the ability to provide the solution with higher competency within less time and a less computationally complex approach. The operation of proposed structure is analyzed and its advantages are justified by comparison with exiting topologies. The effectiveness of RSO based SHE scheme is also verified by comparing it with other nature-inspired algorithms. The effectiveness and workability of the proposed system are examined using simulation and experimental tests.

A modified T-type multilevel inverter for renewable energy applications

The primary challenge in integrating renewable resources into grids using multilevel inverters (MLI) is the need for many separate DC sources and switching device counts. Transformer-based multilevel inverters (TMIs) have emerged to address this issue, aiming to minimize system components and boost source voltage with a single DC source. This research article introduces a novel TMI topology that utilizes only a single DC source and incorporates ten switches to produce good-quality load voltage with high magnitude. The proposed TMI offers several structural advantages, including self-galvanic isolation, reduced switching devices and uniform voltage levels across all turn ratios. Additionally, the TMI operates a switching method called pulse width modulation, which provides the gating pulses to all the power semiconductor devices in the proposed TMI. An experimental model has been created in a laboratory environment, and simulations are performed using the MATLAB/Simulink platform to assess the effectiveness of the suggested TMI. Furthermore, a comparison between the suggested TMI circuit and other recent TMI designs with similar characteristics is performed. This comparison is carried out to assess and validate the superior features of the proposed TMI over the alternative designs.

Standalone and grid-connected operation of single-source multilevel inverter with boosted output voltage

Multilevel inverters produce waveforms that lead to better power quality. Switched-capacitor inverters are one kind that is capable of generating boosted voltage and encourages a single-stage grid-tied inverter solution. In this paper, a four-times boost nine-level inverter with fewer switches is presented in standalone and grid-connected mode. Two switched capacitors, along with eleven switches and one diode, are employed to generate the required boosted nine-level output. The circuit modulation allows self-charging of the capacitors, with the first capacitor charging to the DC source and the second charges to twice of it by shunting it with the combination of the first capacitor voltage and the DC source. This inverter’s application can be as a solar PV microinverter due to its fewer components and small filter requirement. The topology is compared with the single-source nine-level inverters and exhibits the lowest cost of all quadruple boost inverters. The presented inverter operation is verified in Simulink and validated on the laboratory prototype. Further, to minimize the leakage current, the circuit is modified accordingly and tested in a hardware-in-the-loop environment.

A novel modified switched capacitor multilevel inverter using SARC-DQRLC controlling mechanisms for grid systems

Currently, the solar photovoltaic (PV) systems are becoming more and more important in order to meet the world's increasing demand for electricity. In this study, a unique Hybrid Group Search Integrated Rider (HGSR)-MPPT control technique is developed to track the maximum solar energy from the PV panels in order to meet the grid systems' need for electricity. Then, the output voltage of the PV is boosted using the cutting-edge Cuk Step-Up converter, which has a higher voltage gain efficiency and lower stress voltage between the switches. Consequently, the Self-Adaptive Rao Control (SARC) technique is implemented to produce the pulses required to actuate the converter's switching components. More specifically, the improved switched capacitor five-level inverter circuit is modelled in this study to improve the grid unit's power quality with low leakage current, switching stress, and minimal component consumption. In order to improve the performance of the MLI's switching operating modes, the unique Deep Reinforced Q-Learning Control (DRQLC) technique is implemented. The output voltage, current, power, THD, and voltage gain efficiency of the proposed controlling mechanisms' simulation results are evaluated and analyzed.

Control strategies of 15-level modified cascaded H-bridge MLI with solar PV and energy storage system

The rapid integration of renewable energy sources (RES) into power systems emphasizes the need for advanced inverter technology that effectively manages the variability and integration challenges of renewable energy. Multilevel inverters (MLIs), recognized for their ability to minimize harmonic distortion and improve electrical performance, have become increasingly pivotal in addressing these needs. This paper focuses on the challenges associated with integrating MLIs into RES, particularly the complexity of control and coordination required to ensure efficient operation. We present a novel 15-level cascaded H-bridge multilevel inverter optimized for renewable energy applications, incorporating both solar photovoltaic (PV) systems and battery energy storage systems (BESS). The innovative control strategy employed uses a reinforcement learning algorithm to manage the dynamic interaction between the RES inputs and MLI outputs, ensuring optimized performance under varying conditions. The results demonstrate a robust, adaptable MLI design that reduces component count and enhances operational efficiency, thus validating the effectiveness of the proposed MLI in managing the intricacies of renewable energy integration, offering a significant improvement over traditional systems in terms of efficiency and reliability. The study's outcomes have implications for advancing RES integration technologies, marking a step forward in sustainable energy solutions.

Five-Level Inverter-Fed Model Predictive Current Control for a Five-Phase PMSM Drive

In this paper, a five-level inverter-fed Model Predictive Current Control (MPCC) of Five-Phase Permanent Magnet Synchronous Motor (PMSM) Drive is proposed to enhance the performance of the drive by reducing the torque ripples. The MPCC method provides a good steady-state performance and also this method does not require a weighting factor. Among the various torque ripple minimization techniques, the multilevel inverters attracted more attention in electric drives due to rapid development in semiconductor technology. The performance analysis of a five-level (5L) inverter-fed five-phase PMSM drive is compared with two-level (2L) and three-level (3L) inverter drives under various operational conditions. The effectiveness of the proposed method is analyzed using MATLAB/SIMULINK software and also implemented using a real-time simulator.

High-Performance Multi-Level Inverter with Symmetry and Simplification.

This paper presents a high-performance, multilevel inverter with symmetry and simplification. This inverter is a single-phase, seven-level symmetric switched-capacitor inverter based on the concept of the double voltage clamping circuit connected to the half-bridge circuit. Above all, only a single DC power supply is used to achieve a single-phase inverter with seven levels and a voltage gain of three. In addition to analyzing the operating principle of the proposed switched-capacitor multilevel inverter in detail, the stability analysis and controller design are carried out by the state-space averaging method. The feasibility and effectiveness of the proposed structure are validated by some simulated results based on the PSIM simulation tool and by some experiments using FPGA as a control kernel, respectively. However, in this study, the switches were implemented by MOSFETs to meet a high switching frequency. These MOSFETs can be replaced by IGBTs in the motor drive applications so that the used switching frequency can be reduced.

Designing of a Reduced Switch MLI-Based Standalone Solar Inverter Suitable for Water Pump Application

Designing of a reduced switch multi-string cross-connected source type multilevel inverter (CCS-MLI)-based solar pump is introduced in this article. Integration of the Photovoltaic (PV) system with the inverter is achieved through a DC–DC converter equipped with maximum power point tracking (MPPT) to enhance overall reliability. The asymmetrically switched CCS-MLI utilizes only 8 switches to generate 13-level waveform and facilitates power control between battery-assisted PV panels and the single-phase Induction Motor (IM). Multicarrier Pulse Width Modulation (MCPWM) is employed for frequency and fundamental component control in the output voltage. Solar-powered drive systems face the challenge of maintaining intended motor operation amid varying power generation from the PV array. The addition of batteries through a bidirectional DC/DC converter, mitigates this issue by supporting the load during reduced power output from PV panels due to unpredictable solar irradiation levels. Besides ensuring power quality, the proposed control technique realizes constant (V/f) control enabling stable drive operation. The efficacy of the proposed scheme is tested in MATLAB SIMULINK platform with a solar battery combination, considering changing environmental conditions. Furthermore, a hardware prototype of the battery-assisted CCS-MLI-based solar inverter is implemented, and various results are rigorously tested and analyzed using an equivalent machine circuit.

Enhancing power conversion efficiency in five-level multilevel inverters using reduced switch topology

This paper presents extensive research on improving the power conversion efficiency of five-level multilevel inverters (MLIs) by utilizing a reduced switch topology. MLIs have received an abundance of focus because of their ability to generate high-quality output waveforms and have better harmonic outcomes than traditional two-level inverters. The high number of switches in MLIs, on the other hand, can result in increased power losses and lower overall efficiency. In this paper, a novel reduced switch topology for five-level MLIs, which is having five switches is proposed with the aim of minimizing power losses while preserving superior performance due to lesser number of switches. To achieve efficient power conversion, the proposed topology employs advanced pulse width modulation control strategies and optimized switching patterns. The simulation results show that the minimized switch topology improves the power conversion efficiency of the five-level MLI, resulting in lower losses and better overall system performance. The total harmonic distortion (THD) value of the output current has been reduced to 7.12% and the efficiency has been achieved to 96.92%. The findings of this investigation help to advance MLI technology, allowing for more efficient and reliable power conversion in a variety of applications such as renewable energy systems, electric vehicles, and industrial drives.

Novel cascaded switched-diode five level inverter for renewable energy integration

This research presents the usage of a unique five-level cascaded switching diode for medium voltage integration of renewable energy sources. Its primary purpose is to decrease the quantity of gate drivers and switches. In addition to that, the cost and space for the installation of multilevel inverters are less. The inverter topology of novel cascaded multilevel inverters and switched diodes will combine both benefits. One-cycle control (OCC), which is used for clock phase-shifting (CPS) to regulate a two-stage container security device (CSD) multilevel inverter of renewable energy integration, was created to address issues with the multilevel inverter's direct current (DC) source variations. The topology also provides efficiency, harmonic distortion reduction, and voltage output quality. Waveforms are created, and a robust resistance to DC source variations is attained. The viability of the unique five-level inverter using cascaded switched diodes is confirmed by discussing the results of both simulation and experiment.

Solar PV based seventeen level reduced switch symmetrical multilevel inverter topology fed induction motor

Multilevel inverters have received a lot of interest in recent years due to their ability to deliver more voltage levels than typical two-level inverters. Because of this property, multilevel inverters can produce output waveforms that closely resemble sinusoidal waveforms, lowering harmonic distortion dramatically. The emergence of reduced switch symmetrical multilevel inverter topologies has developed the curiosity of many different power conversion systems. These new topologies offer numerous advantages, including greater output voltage quality, fewer harmonic distortions, and increased power conversion efficiency. The inclusion of these inverters in the feeding of induction motors is one of their many prominent uses. A 17 levels of multi-level inverter (MLI) topology is presented with reduced switch count and harmonic reduction for power quality improvement. The inverter is fed by isolated equal photovoltaic panels which act as direct current or DC source. To reduce complexity, switching pulses are generated using hybrid pulse width modulation technique which is designed as controller. Through the use of MATLAB/Simulink, the performance assessment of a unique cascaded multilevel inverter-based reduced switch symmetrical inverter feeding an induction motor drive has been verified. The harmonic distortion with reduced switches obtained is 7.47% which is comparatively less than when compared with conventional cascaded H-bridge topology.

SHE PWM based 21 level inverters with hardware analysis

Recently, the advancement of multilevel inverters (MLI) has been a crucial factor in high power and medium voltage applications. This MLI has multiple topologies and has been used in a variety of applications. Cascaded MLI is preferred over other forms of multilevel inverter topologies. Nonetheless, significant obstacles are encountered when implementing these topologies. They necessitate an increased number of switches, DC sources, capacitors, and diodes. Increased losses and total harmonic distortion (THD) will be present in the system. In addition, the MLI is more expensive. The better construction of a multilevel inverter results in more output levels with fewer switches, sources, and driver circuits, as well as low THD. A new single-phase cascaded asymmetrical DC voltage sources based multilevel inverter design and the selective harmonic elimination (SHE) approach are used to attain these goals. After confirming in MATLAB/Simulink, the hardware implementation of the multilevel inverter in 21 levels was completed in this article.

Performance analysis for induction motor fed by reduced switch symmetrical multilevel inverter topology

Due to its capacity to supply more voltage levels than conventional 2-level inverters, multilevel inverters have attracted a lot of attention in recent years. Multilevel inverters may produce output waveforms that nearly approximate sinusoidal waveforms because to this characteristic, which also significantly lowers harmonic distortion. In many different power conversion systems, the introduction of reduced switch symmetrical multilevel inverter topologies has drawn significant interest. Numerous benefits, such as higher output voltage quality, reduced harmonic distortions, and increased power conversion efficiency, are provided by these novel topologies. The inclusion of these inverters in the feeding of induction motors is one of their many prominent uses. In this paper, a generalized topology is presented that generates nine levels using nine switching devices. To reduce complexity, switching pulses are generated using a low frequency pulse width modulation technique. MATLAB/Simulink is used to analyze the performance assessment of a unique three-phase symmetric cascaded multilevel inverter-based reduced switch symmetrical inverter fed induction motor drive, brushless DC (BLDC) motor and grid has been verified. According to the findings the total harmonic distortion (THD) is found to be 15% for a three-phase system and as the number of levels increases to 17 level the THD is 7.10%.

Comparative Analysis of 5-Level and 7-Level Single-Phase Cascaded H-bridge Multilevel Inverters

The demand for high-performance, efficient, and reliable power electronic systems has been steadily increasing in various industrial applications, including renewable energy systems, electric vehicles, and smart grids. In response to this demand, the Cascaded H-Bridge Multi-level Inverter (CHB-MLI) has emerged as a promising solution, offering advantages such as improved voltage waveform quality, reduced harmonic distortion, and enhanced power handling capabilities. The CHB-MLI is characterized by its modular structure, comprising multiple H-bridge cells cascaded in series. Each H-bridge cell operates with a separate DC power source, enabling the generation of stepped voltage levels at the inverter output. By intelligently controlling the individual H-bridge cells, the CHB-MLI achieves the synthesis of a high-quality multilevel output voltage waveform. The different multi-level inverter topologies are Diode-Clamped MLI, Capacitor-Clamped MLI and Cascaded H-bridge MLI. This paper focused on key aspects like design, simulation, control strategies, performance evaluation, overall comparison and analysis of 5-level and 7-level CHB-MLIs. By addressing these aspects, this paper aimed to contribute to the advancement of power electronics technology and promote the adoption of the CHB-MLI in real-world applications, fostering energy efficiency and sustainability in power conversion systems. Index Terms: Inverter, Multi-level inverter, CHBMLI, switching, SPWM, MCSPWM, gate signal, waveform, harmonics, THD, MATLAB.

Fundamental frequency switching strategies of a seven level hybrid cascaded H-bridge multilevel inverter

This paper presents a novel hybrid cascaded H-bridge multilevel inverter (HCHB MLI) designed to address the growing importance of multilevel inverters in the context of renewable energy sources such as solar, wind, and fuel cells. The proposed topology features eight insulated-gate bipolar transistor (IGBT) switches and utilizes two distinct input direct current (DC) sources: a battery and a capacitor, making it a hybrid system. The control strategy employed in this topology is based on fundamental switching frequency techniques. Simulation results of the proposed topology are conducted using MATLAB/Simulink software, while hardware experimentation with a single-phase H-bridge inverter is also demonstrated in the paper. For pulse generation and IGBT switch control, an Arduino UNO microcontroller is utilized. The output voltage of the single-phase H-bridge inverter is verified through experimentation using a cathode-ray oscilloscope (CRO).