Three-phase Multilevel Inverter Research Articles

Single source self balanced switched capacitor based singe phase nine level inverter

Multilevel inverters are becoming increasingly significant due to their ability to efficiently convert power in various applications such as renewable energy systems, electric vehicles (EVs), and industrial drives. The growing need for efficient power conversion in these areas has driven heightened interest in multilevel inverters. High inrush current is required for numerous applications, including variable frequency drives, single-phase or three-phase machine drives, locomotives, electric vehicles. However, managing this inrush current is crucial to prevent damage to the power source and other connected equipment, as well as to ensure smooth and reliable operation. The solution for this is to provide isolation between load and source. The proposed single phase switched capacitor multilevel inverter possess the feature of virtual isolation between the load and the source. This topology consists of a switched capacitor cell network and a multilevel inverter. In this work, a simplest architecture is used for the MLI section to reduce the number of switches. The MLI section consists of only eight switches. Although the switched capacitor network in this topology consists of a higher number of switches, the switches in the network carry only very low current, resulting in negligible losses. Additionally, the switched capacitor network is highly modular in nature. The proposed single-phase inverter can be converted to a three-phase multilevel inverter (MLI) by connecting identical units in each phase, with the reference sinewave signal for the pulse-width modulation technique derived from the corresponding phases. Consequently, this proposed topology is suitable for both low-power and high-power applications. This work demonstrates that self-voltage balancing of the level capacitors can be achieved without the need for auxiliary components.In this design, the level capacitors act as the source to the load and are charged through switched capacitors. The voltage THD in the suggested work is less than 5%, which is in accordance with IEEE 519 standards. High voltage gain, better load, and line regulation, are other significant advantages of this novel topology. Another feature of this work is simplicity in design and can be easily extended to higher voltage levels. Comprehensive simulation and experimental results are provided to validate the precise performance of the proposed multilevel inverter

Hybrid feedback control of PMSG-based WECS with multilevel flying-capacitor inverter enhanced by fractional order extremum seeking

This paper proposes an original hybrid control strategy for a three-phase multilevel flying capacitor inverter (FCI) used in wind energy conversion system (WECS). A state feedback law, computed using a Lyapunov function and an invariance principle, is designed to manage grid current control and capacitor voltage balancing, guaranteeing the asymptotic stability of the closed-loop system. Additionally, a fractional-order extremum seeking control (FOESC) algorithm for Maximum Power Point Tracking (MPPT) is introduced, which optimizes power capture by adjusting turbine speed from the DC side without requiring a detailed system model (model-free approach). The use of fractional-order calculus leads to improved convergence and more seamless performance while preserving the robust characteristics of the system. The proposed control strategies are validated through simulation, demonstrating improved transient response and stability under varying wind conditions and parameter uncertainties. These results highlight the potential of advanced control algorithms to enhance the efficiency and reliability of wind energy systems, contributing to global efforts to achieve sustainable energy goals.

Design and implementation of single DC-link based three-phase multilevel inverter with CB-PWM techniques

Simulation and implementation of a single DC-link-based three-phase inverter are investigated in this article. The primary focus is on designing a single DC-link three-phase inverter for high power applications. Unlike conventional inverters that require 600 V to generate 400 V (RMS) at the output, the proposed system achieves this with only 330 V, facilitated by a 12-terminal 1:1 transformer. The system employs Proportional Integral (PI) and Neural Network (NN) controllers to optimize performance. Various Carrier-Based Pulse Width Modulation (CB-PWM) techniques, including Phase Disposition (PD), Phase Opposition Disposition (POD), and Alternative Phase Opposition Disposition (APOD), are implemented and evaluated based on Total Harmonics Distortion (THD) concerning the Modulation Index (MI) of the inverter. The proposed inverter achieves a THD reduction to 4.8%, demonstrating superior performance compared to recent studies. The system’s performance is validated through extensive MATLAB/Simulink simulations and practical implementation using XILINX FPGA software, confirming the efficacy of the proposed design.

A Three-Phase Multilevel Inverter Synthesized with 31 Levels and Optimal Gating Angles Based on the GA and GWO to Supply a Three-Phase Induction Motor

A three-phase multilevel inverter (MLI), synthesized with 31 levels in regard to its output voltage, is used to provide the AC supply to a three-phase, squirrel cage induction motor. The gating angles required for the 30 power switches on the MLI are optimized using both the genetic algorithm (GA) and the grey wolf optimizer (GWO), in which the optimal angles are determined through solving the trigonometric equations taken from Fourier analysis to target the minimum total harmonic distortion (THD) at the MLI output. A simulation model and an experimental prototype are developed for performance analysis and validation. The results demonstrate that the MLI is effectively able to produce 31 levels of three-phase AC output voltage, with the THD not exceeding 5% when loaded with a resistive load and a three-phase induction motor. The voltage and current are measured and recorded for different loads and operating conditions, including the amount of energy consumed by the load. The results of the frequency analysis demonstrate that most of the triple harmonics, which can harm the efficiency of the inverter, are cancelled.

Analysis of the performance of a 25-level inverter with a minimum number of switches and reduced harmonics for an environment solar energy

A multilevel inverter is a type of electrical equipment that converts a DC voltage to a higher AC value by creating a stepped waveform using several voltage levels. Multilevel inverters may create waveforms with three or more voltage levels, although regular inverters cannot. This separation results in lower harmonic distortion, decreased electromagnetic interference, and higher efficiency. An innovative MLI design that makes use of fewer switches and PV sources solves this problem. The Perturbation and Observation (P&O) approach is used to derive the Maximum Power Point Tracking (MPPT) from these PVs. The MC-SPWM technique was used in the design, simulation, and construction of single-phase and three-phase multilevel inverters with inverter levels ranging from three to twenty-five. The technique's cornerstones are phase disposition (PD-PWM) and power quality improvement. The main goal of the paper objectively analyzing the issue of power-system harmonics, providing information on causes, effects, and useful harmonic mitigation strategy.

An Application of Neural Network-based Sliding Mode Control for Multilevel Inverters

Multi-level 3-phase inverters using cascaded H-bridges are becoming prominent in the electric drive and renewable energy sectors due to their high capacity and ability to withstand high voltage shocks. Therefore, the modulation and control techniques used in these multilevel inverters have a crucial influence on the quality of the output voltage they produce. The significantly high common-mode voltage amplitude they generate is one of their disadvantages, causing leakage currents and harmonics. This article proposes a new technique using sliding mode control combined with neural networks to manage a three-phase multi-level inverter. The research objective of this innovative technique is to eliminate the need for current controllers and conventional modulation that relies on carrier signals, reducing hardware calculations and enhancing dynamic response. In addition, it demonstrates the ability to minimize harmonics, common mode voltage, and the number of switching counts, thereby limiting the inverter switching losses and increasing device performance. Simulation results performed on a 5-level 3-phase inverter using cascaded H-bridges have confirmed the effectiveness of the proposed method.

Enhanced low voltage ride-through control of multilevel flying capacitor inverter based wind generation

This paper introduces a cost-effective control method to enhance the low voltage ride-through (LVRT) capability and smooth the output power of a three-phase multilevel flying capacitor inverter (FCI) in wind turbine-based permanent magnet synchronous generator (PMSG). The proposed approach utilizes the energy storage capability of flying capacitors to mitigate wind power fluctuations and address short-duration outages and deep voltage sags. Additionally, a nonlinear controller based Lyapunov theory is developed to regulate capacitor voltages, improve power factors, and balance DC-link voltage. Numerical simulations are conducted in MATLAB/SimPower systems environment to validate the effectiveness of this comprehensive control strategy across different grid operation scenarios.

A quad DC source switched three-phase multilevel DC-link inverter topology

The concept of an isolated DC source cascaded multilevel inverter finds good solutions for generating quality output voltage for low-medium power applications. It shapes the output voltage from three levels into a number of steps closer to a sinusoidal shape using small DC sources or batteries. Several advantages have been sighted like lower voltage stress and bearing noise, and lesser THD. However, a common issue in the MLIs is the total components required which increase with the rise in voltage levels. This paper proposes a three-phase MLI design having several isolated quad voltage source modules including an H-Bridge inverter. The design suggested claims reduced switching components for current conduction paths showing improved output quality. The operational features of the suggested MLI have been analyzed using Matlab/Simulink software, furthermore, an experimental module is constructed for demonstrating the effectiveness of the simulated results.

A Single Stage Photovoltaic Solar Pumping System based on the Three Phase Multilevel Inverter

This paper presents a study of a single-stage DC-AC converter for a solar water pumping application. The topology was based on solar panels connected to a new structure of a three-phase multilevel inverter through DC-bus capacitors. The inverter offers simplicity, requires fewer components compared to conventional ones, and provides optimal voltage and current waveforms with reduced harmonics, eliminating the need for filters. The applied control technique aimed to stabilize the input DC-bus voltage, extract the maximum power using a simple MPPT algorithm, and enhance the efficiency of the water pump through scalar V/f control, regardless of weather changes. A simulation was conducted using the PSIM software, considering a variable daily climate scenario. The results obtained demonstrate the efficiency of the system in extracting energy with optimal torque and current for the pump compared to a classic design based on a three-phase H-bridge inverter.

Medium-Voltage Drives (MVD) - Performance Analysis of Seven-Level Cascaded H-Bridge Multilevel Driver

The drawbacks of traditional inverters, particularly in high-power applications and medium voltage, have been highlighted in previous investigations. Due to the cascaded H-bridge multilevel driver (CHBMD) harmonic characteristics improved and power enhanced, inverters with multiple levels are increasingly popular for high-power applications. The scientific literature has documented works on multilevel inverter topologies, control strategies, and applications. Additionally, no conclusive results investigate or rate a three-phase multilevel inverter's effectiveness. The present investigation evaluates the performance of a multi-carrier sinusoidal pulse width modification (MCS-PWM) based, Seven-Level cascaded H-bridge multilevel driver (7LCHBMD). Performance assessments develop based on the outcomes of a modeling experiment on the CHBMD functionality utilizing MATLAB. The characteristics of the results chosen to perform the task were the harmonic range, waveform arrangement, and essential significance reducing the THD output of the 7LCHBMD. The MCS-PWM technique procedure from the perspective of the voltage line had been determined according to the findings of the simulation investigation and analysis carried out for the 7LCHBMD utilizing the PD-PWM as the control framework.

A Novel High-Efficiency Three-Phase Multilevel PV Inverter With Reduced DC-Link Capacitance

We present a novel three-phase multilevel inverter (MLI) design for PV applications that does not require large DC-link capacitors to buffer the 120 Hz power ripple and allows individual inverter module to process trapezoidal power instead of sinusoidal power. This new design features two inverters connected in parallel to each DC source and N inverters connected in series to each grid phase to support the grid voltage. The trapezoidal operation improves the overall system&#x2019;s efficiency by allowing the inverter module to output peak or zero power for most of the AC cycle. We present the controller design and simulate the proposed MLI system in PLECS. We demonstrate an experimental 110<inline-formula><tex-math notation="LaTeX">$V$</tex-math></inline-formula> DC input, 208 <inline-formula><tex-math notation="LaTeX">$V_{rms}$</tex-math></inline-formula> three-phase AC output, 1kW 5-level prototype with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;95&#x0025; efficiency. With the same inverter module, we compare the efficiency of the proposed design to the conventional MLI design, where all modules share phase power evenly. We demonstrate that the proposed design consistently outperforms the conventional design in efficiency, with <inline-formula><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula>&#x00A0;20&#x0025; loss reduction at light load conditions.

Two Compact Three-Phase Multilevel Inverters for Low-Voltage Applications

In this article, two compact three-phase multilevel inverters are proposed. The first proposed topology consists of three dc sources and ten power switches. The merit of the first proposed topology is reducing two switches from its structure to the conventional topologies. The second proposed topology is similar to the first one, except that one of the dc sources is replaced by a capacitor. This capacitor is balanced by an additional switch and one of the dc sources. How to apply two modulation methods for these inverters has been studied in detail. These modulation methods are level-shifted pulsewidth modulation and phase-shifted pulsewidth modulation (PS-PWM). Also, the value of the capacitor for each of the modulation methods has been calculated. Finally, the experimental results are provided to confirm the performance of the proposed topologies.

Current-THD minimization in multilevel inverters with variable DC ratios utilizing a generic closed-form analytic formulation of line-voltage WTHD

This article presents a generic approach to load-current THD minimization in hard-switched Staircase Modulation (SCM) based three-phase (3ɸ) Multilevel Inverters (MLI) with either fixed or variable DC source Ratios (DCR). First, a computer-aided closed-form analytical formulation of Weighted THD (WTHD) applied directly to line-voltage waveforms is derived using Maple software and then verified against numerically-obtained results of previous works. The proposed symbolic analysis of Weighted Line-voltage THD (WLTHD) applies to 3ɸ-MLIs of any topology with Equal Voltage Steps (EVS) or Unequal Voltage Steps (UVS), and any number of voltage levels count (N), either odd or even. Such an analytical approach eliminates the risk of underestimation errors associated with numerical methods. The proposed closed-form WLTHD expression is then utilized for optimal minimization of current-THD in 3ɸ inductive loads with unconnected neutral. This is achieved by introducing a generic UVS-based Optimal Minimization of WLTHD (OMWLTHD), which calculates the optimum Phase Switching Angles (PSA) and the supply DC-Ratios (DCR), given any desired Modulation Index (MI), thus ensuring minimum current-THD across the entire linear MI range. The revealed OMWLTHD approach is fully validated by both digital simulations and controller plus hardware-in-loop (C-HIL) based experiments, using 7-, 8-, and even 13-level 3ɸ-MLIs of both EVS and UVS configurations. Furthermore, to reveal the impact of WLTHD minimization on actual load current-THD, the MLIs were loaded by a Resistive-Inductive-EMF (RLE) load, as well as a 3ɸ squirrel cage induction motor, thus representing a wide range of possible loads, such as motors and ac grids. The conclusive verification results have shown that in the case of 3-wire inductive loads with a power factor up to 0.95, the proposed UVS-based WLTHD optimization is more beneficial for current-THD minimization over other harmonic distortion quantifying parameters, as WLTHD presents the strongest correlation to actual load current THD when tested against any other parameter such as phase and line THD or WTHD. The revealed improvement in current THD was even more pronounced for UVS-based SCM compared to traditional EVS-based SCM. Additionally, MATLAB and Maple source files of the proposed WLTHD formulations and Excel-based pre-calculated optimum PSA and DCR sets for different values of N are provided as downloadable links to further enhance the contribution of the article.

Dual Three Phase Multilevel Space Vector Modulation Control of Diode Clamped Inverter for Dual Star Induction Motor Drive

This work suggests a dual three-phase Space Vector Modulation (SVM) for the Diode Clamped Multilevel Inverter (DCMI) to ensure a robust control of Dual Star Induction Motor (DSIM). The principal scheme is investigated to apply the same control of the six-phase multilevel inverter by two three-phase multilevel inverter to drive the DSIM. The use of classic SVM control offers significant simplifications for controlling a six phase five levels inverter. The proposed control approach employs according to the hybridization of various conversion functions to establish the modulation strategy for each voltage vector and its placement in the plane of voltage modulation in distinctly and easy manner. A numerical simulation under MATLAB/Simulink is carried out to evaluate the Indirect Field Oriented Control (IFOC) of DSIM drive fed by multilevel inverters. The simulation outcomes clearly reveal good performance of the designed control strategy in terms of THD and control efficiency.

Online Failure Diagnostic in Full-Bridge Module for Optimum Setup of an IGBT-Based Multilevel Inverter

An online failure diagnostic test is essential to ensure the robustness and reliability of high-powered systems. Furthermore, the overall design must comprise diagnostic strategies to detect in-service and high-powered module defects. This paper describes the critical failure mechanisms––cross-conduction, inductive avalanche, second turn-on, VS-undershoot, inrush current, and thermal runaway––that directly affect insulated gate bipolar transistor (IGBT) operation. The constructed inverter contains 18 transformer-based taps (six per phase); however, this work studied a single tap (IGBT-based full-bridge module) to understand the reasons for failure and the routes to mitigate them. Moreover, a cost-effective solution using the IR2127STRPBF driver circuit was implemented to reduce the probability of thermal runaway in case of overcurrent, short-circuit, or avalanche events. For this reason, the electrical current state was adjusted using an FPGA digital resource to perform dynamic PWM control signals. The obtained correlation waveforms are valuable for verifying diagnostic data at the design stage to emphasize the significance of evading premature failure events. The comprehensive study on failure diagnosis enabled successful design strategies to construct a robust 45 kVA three-phase multilevel inverter for a 22 kW eolic-photovoltaic generation plant.

An adaptive harmonic abatement in three-phase multilevel inverter topology with reduced switches using metaheuristic approaches for renewable energy applications

ABSTRACT Renewable energy sources like solar, wind, and fuel cell are the medium sources of energy to produce high output power. The power electronics conversion in the renewable energy system is the significant drawback of poor-quality output due to its harmonic content and switching losses due to its increasing number of switching components. This article proposes a novel three-phase Multilevel Inverter (MLI) topology based on a series-parallel switched multilevel dc-link inverter configuration with a reduced number of switches that minimize the lower-order harmonics 3rd, 5th, and 7th using Selective Harmonic Elimination (SHE) based on the Particle Swarm Optimization (PSO) algorithm. The configuration also engages the Artificial Neural Network (ANN) to provide optimum switching angles for varying input voltages over a period, as in the case of renewable energy applications. The output of the MLI and its harmonic profile are examined in the MATLAB/Simulink platform. The hardware results are proven with the Xilinx-based FPGA Nexys-4 board that generates discrete pulses to the switches.

A novel cascaded transformer coupled multilevel inverter with reduced number of switches for high power applications

PurposeThe purpose of this paper is to design a cascaded Multilevel inverter with reduce number of switches for high power applications. This paper came up with an innovative three-phase multilevel inverter (MLI) topology, which is a cascaded structure based on classical three-legged voltage source inverter (VSI) bridges as an individual module. The prominent advantage of this topology is that it requires only one direct current (DC) link system. The main characteristic of it is that a higher number of voltage levels can be achieved with considerably a smaller number of semiconductor switches, which improves the reliability, power quality, cost and size of the system significantly.Design/methodology/approachThe individual modules are cascaded through three-phase transformers to provide higher voltage at the output with the higher number of voltage levels. In this work, the phase-shifted pulse width modulation technique is implemented to verify the result.FindingsThe proposed topology is compared with three-phase cascaded H-bridge MLI (CHB-MLI) and a modified CHB-MLI topology and found better in many aspects. The proposed MLI can produce a higher number of voltage levels with fewer semiconductor switches and associated triggering circuitry. As the device count in the proposed MLI is less compared to other MLI discussed, it tends to have less switching and conduction loss which increases the efficiency and reliability. As the number of level increases, the voltage profile and the total harmonic distortion of the proposed MLI improves.Originality/valueThis is a transformer-based modular cascaded MLI, which is based on classical VSI bridges. Here in this topology, a single module provides all three phases. So, a single string of cascaded modules is enough for three-phase multilevel voltage generation.

An advanced HBNP multi-level inverter for the performance enhancement with reduced components

ABSTRACT This article proposed an advanced three-phase multilevel inverter called the H-Bridge Neutral Point (HBNP) Inverter, with a minimum number of components. This inverter is designed to generate five-level output voltage using a single solar system in each phase, making it suitable for low-, medium-, and high-power applications like AC drives, grid integration of renewable energy sources, electric vehicles, and high voltage DC and AC transmission systems, etc. The proposed circuit configuration has reduced gate driver circuits, less capacitors, fewer input sources, modularity in structure, and better THD. Furthermore, the hybrid PWM control technique provides switching signals and ensures that all switches have equal conduction intervals. All of the switches have the same temperatures and voltage sharing, indicating a simpler thermal design and DC bus voltage balancing. The proposed and existing topologies are validated using MATLAB Simulink, and the proposed topology prototype is implemented in the laboratory.

Modified T-type topology of three-phase multi-level inverter for photovoltaic systems

In this article, a three-phase multilevel neutral-point-clamped inverter with a modified t-type structure of switches is proposed. A pulse width modulation (PWM) scheme of the proposed inverter is also developed. The proposed topology of the multilevel inverter has the advantage of being simple, on the one hand since it does contain only semiconductors in reduced number (corresponding to the number of required voltage levels), and no other components such as switching or flying capacitors, and on the other hand, the control scheme is much simpler and more suitable for variable frequency and voltage control. The performances of this inverter are analyzed through simulations carried out in the MATLAB/Simulink environment on a three-phase inverter with 9 levels. In all simulations, the proposed topology is connected with R-load or RL-load without any output filter.

A Symbiotic Organism Search-Based Selective Harmonic Elimination in a Switched Capacitor Multilevel Inverter

Multilevel inverters are increasingly being employed for industrial applications, such as speed control of motors and grid integration of distributed generation systems. The focus is on developing topologies that utilize fewer lower-rating switches and power sources while working efficiently and reliably. This work pertains to developing a three-phase multilevel inverter that employs switching capacitors and a single DC power supply that produces a nine-stage, three-phase voltage output. A recently proposed powerful meta-heuristic technique called symbiotic organism search (SOS) has been applied to identify the optimum switching angles for Selective Harmonic Elimination (SHE) from the output voltage waveform. A thorough converter analysis has also been done in the MATLAB/SIMULINK environment and is validated with the real-time hardware-in-the-loop (HIL) experiment results.