Neutral Point Clamped Multilevel Inverter Research Articles

Phase disposition PWM control topology based: A novel multilevel inverter with reduced switch for power electronics applications

In the field of industrial drive applications, a neutral point clamped multilevel inverter (NPC MLI) is an extensively used option. The NPC MLI architecture involves more number of components for higher level and higher switching frequency operation. In this work paper, a novel three-phase 3-Level MLI is proposed evading the usage of clamping diodes and quadratic switches. Additionally, phase disposition pulse width modulation (PD-PWM) control technique is also employed for the proposed MLI. In comparison to NPC MLI, proposed MLI reduces the voltage switching stress as only one switch is operated per inverter leg. Another feature is that there is a considerable reduction in power losses as the current flows only through fewer elements. The proposed 3L inverter topology is explored thoroughly using the MATLAB simulation model. The evaluation of results is also demonstrated concerning the proposed PD-PWM technique by comparing its performance with the conventional sinusoidal PWM method. The Real-Time hardware-in-loop (HIL) simulator is also used to validate the simulation outcomes of the proposed model.

Switch fault identification scheme based on machine learning algorithms for PV-Fed three-phase neutral point clamped inverter

Any faults in power electronic switches must be detected and located promptly to certify the unchanging operation and reliability of multilevel inverter (MLI) systems. Machine learning (ML) techniques are increasingly being utilized to diagnose faults in MLIs due to their advantages, such as high precision, less calculation time, and reduced complexity. A faulty switch identification and phase identification method based on different ML classifiers is presented in this paper, explicitly targeting open-circuit faults in switches in a PV-fed 3-phase three-level Neutral Point Clamped (NPC) inverter. The NPC MLI output voltage and current signals are input signals to classify faults. The information or essential feature from the raw voltage and current data is extracted using a recursive discrete Fourier (RDF) followed by a discrete wavelet transform (DWT). Finally, the standard deviations of the approximate and detailed coefficients are used as input for ML algorithms. To do the comparative analysis, a variety of ML techniques are then applied to these features, including logistic regression (LR), random forest (RF), quadratic discriminate analysis (QDA), K-nearest neighbour (K-NN), and support vector machines (SVM). The experiment results indicate that the RF algorithms achieve the highest classification accuracy of 99.59 % for various switch fault conditions.

EFFECT OF VOLTAGE STRESS ON RELIABILITY OF THE 3-LEVEL ANPC MULTILEVEL INVERTER FOR WIND TURBINES

Wind power with low or no greenhouse gas emissions has been highly prevalent over the last decade. Modern renewable energy systems rely heavily on power electronic devices such as multilevel converters (MLC) to integrate renewables into the grid or provide electricity to islanding loads. These converters’ power electronic switches have a high failure rate (approximately 34 percent). As a result, the reliability evaluation of these converters is vital. Most research has focused on developing a fault-tolerant, efficient and cost-effective topology that reduces components. Still, the reliability of these topologies has received relatively little attention. This paper studies the effect of voltage stress on three-level Active Neutral Point Clamped (ANPC) multilevel inverter reliability. The series redundancy is introduced in ANPC using redundant outer switches, making ANPC a fault-tolerant topology. The reliability of this fault-tolerant topology is compared with the fault-intolerant ANPC. The voltage stress factor is calculated for fault intolerant and proposed fault-tolerant ANPC topologies. Because of the reduced stress on the switches and redundant configuration of the outer switches, the proposed fault-tolerant ANPC is more reliable. The fault-tolerant topology proposed in this paper has the lowest voltage stress factor, resulting in better reliability.

Simulation of 3D-space vector modulation for neutral point clamped inverters

This paper gives an idea to simulation of three-dimensional space vector modulation for neutral point clamped multilevel inverter. Three dimensional-space vector modulation (3D-SVM) algorithm is progressed method of two dimensional-space vector modulation (2D-SVM) algorithm; it leads to reduce the complexity in reference vector identification and switching time calculation, also it includes the various advantages of 2D-SVM like minimized total harmonic distortion, reduced EMI issues. A simple system for the assortment of switching state vectors to track the reference voltage vectors without using any redundant switching vectors. This proposed method tracks the reference vector by identifyinglsubcubes and prisms by using mathematicallconditions. Here the cost of the proposedltechnique is independentlof voltagellevels oflinverter. This paper realizes the accomplishment of 3D-SVM using a neutral point clamped inverter. The simulation results of the proposed method are verified using MATLAB/Simulink.

Load Voltage Control of a Wind Turbine-driven Three-phase Squirrel-Cage Induction Generator in an Islanded Microgrid

The intermittent nature of the wind resources and reactive power consumptions are major issues associated with squirrel cage induction generator wind power system when operated in an island microgrid mode. The resultant effect of these two issues are continuous fluctuations of load voltage which has adverse effects on electrical devices. This paper proposes a voltage regulation technique based on proportional controller and phase deposition sine pulse width modulation (PDSPWM) for the control of 5-level neutral point clamped multilevel inverter. The instantaneous voltage tracking strategy based on root mean square value of microgrid voltage was adopted to regulate and maintain the output load voltage at 400 𝑉𝑟𝑚𝑠 despite rotor fluctuations with wind speeds. The simulation was carried out in a MATLAB/SIMULINK environment and the performance of the control scheme was found to be excellent.

Assessment of harmonic mitigation performance of electric springs with different inverter topologies

Electric spring (ES) is a new technology inspired by the idea of realization a system that is equivalent to mechanical springs in terms of functionality within power systems. Electric springs are comprised from a DC voltage source, an inverter and an LC filter at the grid side. It can be used effectively in power systems to perform many functions such as voltage regulation, reactive power compensation, demand management and energy storage. On the other hand, due to the semiconductor elements in ES structure, it causes distortion on voltage and current waveforms. However, various control approaches have been proposed in the literature in order to prevent the aforementioned distortions. In this study, three different ESs has been modeled with the inverter topologies chosen from the frequently preferred once used in applications, namely Half-Bridge, Full-Bridge, and Neutral Point Clamped Multi-Level Inverter (NPC-MLI). The disruptive effects of electric springs with different inverter topologies on the grid and their performance in harmonic elimination have been examined through the results obtained from simulations realized in MATLAB/Simulink®.

A new design of active NPC converter topology with higher voltage gain for solar PV applications

In the low voltage applications, the high gain multilevel inverters has seen more visibility due to the improved harmonic profile with multilevel voltage as well as boosting feature. A boost active neutral point clamped (ANPC) multilevel inverter (MLI) configuration with reduced resource count has been proposed in this paper. The proposed MLI produces 11 levels (11L) voltage with the help of 12 switches of blocking voltage ratings lesser than the peak value of output voltages. For attaining the boosting of 2.5 in output voltage, 4 capacitors are used in the proposed MLI which are inherently self-balanced. The capacitors charging as well as discharging are done by implementing the simple logic of parallel/series connection with the active power DC source. The proposed MLI is implemented and tested in the laboratory at various operating conditions, and the corresponding results and discussion are presented.

Performance Evaluation of Solar PV-Based Z-Source Cascaded Multilevel Inverter with Optimized Switching Scheme

AC loads may demand a fixed or variable voltage at their input terminals. When using inverters to power such loads, the response of the inverter must be precisely controlled to suit the demands of the AC loads. Inverters with higher efficiency and sensitivity will play an increasingly essential role as the need for solar PV applications in prospective green technology grows. To increase power quality and provide a reliable power source, an inverter architecture with harmonic reduction approaches is proposed. The multilevel inverter (MLI), unlike conventional inverters, is developed by cascaded single inverter units and is often used to connect renewable energy sources. As a result, they can be utilized to efficiently reduce harmonics. Among the three topologies, the most widely used in industries is the neutral-point clamped MLI. When the levels are raised, however, they demand a larger number of diodes. When the level of the flying capacitor exceeds three, several capacitors are necessary. As a result, the optimum option for synthesizing the right output voltage from several DC sources is a cascaded multilevel inverter (CMLI). Each link in a CMLI is connected by a single DC source; therefore, there is no voltage imbalance. However, getting equal DC voltages at the input of each unit is once again a limitation. In this work, various existing multilevel inverter topologies including hybrid topologies with different switching strategies are investigated and reported. The performance of a solar PV-based seven-level quasi-Z-source cascaded H-Bridge MLI (qZS-CHBMLI) has been thoroughly examined with the best switching scheme and best topology of multilevel inverters using MATLAB/Simulink.

Design of Three Level Neutral Point clamped inverter with Fuzzy logic based MPPT for PV applications.

In this paper a solar photovoltaic (PV) system with maximum power point tracking (MPPT) for domestic low power applications. The proposed system contains a PV array which provides electrical power, while a DC/DC converter is incorporated to regulate the power derived from PV panels. Fuzzy logic control (FLC) based MPPT has been proposed. To convert the DC voltages and currents obtained from Solar panels to AC voltages and currents, a Neutral point clamped multilevel inverter is included. Furthermore, harmonics are removed by using the LCL filter. The PV system working, design of the DC/DC Boost converter, Novel MPPT techniques, Multilevel inverter topologies and LCL filter design are explained. Results reveal that the FLC based MPPT has much lesser total harmonic distortion (THD) in the PV system. With this property, FLC possesses faster convergence than the perturb & observe (P&O) and other MPPT techniques.

Minimization of total harmonic distortion in neutral point clamped multilevel inverter using grey wolf optimizer

<span lang="EN-US">The inverter has been attracting researchers for their application in renewable energy. So far, multilevel inverter is considered as low distortion class, which produces multilevel output voltage imitating a pure sine waveform. However, the needs for free distortion of output voltage have been motivating to improve multilevel pulse width modulation PWM generation method. In this paper, the modified PWM technique is proposed to reduce the voltage total harmonics distortion (THD) of multilevel inverter. This modulation technique is then applied to control a single-phase threelevel neutral point clamped multilevel inverter (NPC-MLI). Grey wolf optimizer (GWO) algorithm is utilized to generate optimal amplitude and phase shift of modified reference signal. The GWO algorithm is then compared with other optimization algorithms such as differential evolution (DE), human psychology optimization (HPO), and particle swarm optimization (PSO) to evaluate their performance in harmonic minimization. The performance of the proposed work is validated through simulation and experimentation on a prototype. The results show that the modified PWM technique optimized with GWO can reduce THD on NPC-MLI output voltage.</span>

A grid interconnected nested neutral-point clamped inverter with voltage synchronization using synchronous reference frame controller

<p><span lang="EN-US">Nested neutral-point clamped multi level inverter with inter connection to grid through the synchronous reference frame (SRF) controller for synchronization of voltage to the grid is demonstrated. The system's main feature is that voltage stress in each inverter switching device is kept to a minimum, and redundant inverter switching states are utilised for neutral point and flying capacitor voltage balancing with sinusoidal pulse-width modulation (PWM) technique, synchronisation to grid voltages, and power injection with low harmonic generation. The inverter receives its input from a photovoltaic (PV) source that is coupled to DC-DC booster converters that are regulated by the maximum power point <span lang="EN-US">(MPP)</span> tracking incremental conductance algorithm to maintain a constant dc voltage. The system is examined under various load conditions with MATLAB/Simulink model.</span></p>

Review of reduced‐switch multilevel inverters for electric vehicle applications

AbstractThis paper deals with the detailed review and comparative analysis of latest reduced switch multilevel inverter topologies for electric vehicle applications. The recent trends in reduced‐switch multilevel inverters are discussed. Detailed review of the reduced‐switch multilevel inverter topologies, their merits and demerits, and the comparative analysis based on component count, total harmonic distortion, and efficiency are conducted. This paper gives a detailed review of recent trends in reduced‐switch multilevel inverter topologies for electric vehicle applications. Switching pattern of the topologies is provided for better understanding of the inverter operation. Comparative analysis of the reduced‐switch inverter topologies based on the component count, total harmonic distortion of output voltage, and efficiency is also presented in this paper. Based on the comparative analysis, it is observed that the interleaved nine‐level flying capacitor multilevel inverter topology achieved the lowest output voltage distortion of 1.6%, which is within the acceptable limits of IEEE 519‐2014 standard. It is observed that the three‐level active neutral point clamped multilevel inverter topology achieved the highest working efficiency of 99.4%. This paper discusses the most recent trends in reduced‐switch multilevel inverters. A comprehensive review of the recent publications and a crisp comparative analysis of the different inverter configurations based on component count, harmonic distortion of output voltage, and efficiency are presented in this paper.

Power Converters in Power Electronics [Book News

This book includes carefully selected papers on power electronic converters and their control, mainly impedance source converters, current-source inverters with ac-side clamping, three-level quasi-switched boost T-type inverters, flying capacitor pulse width modulation and FC multilevel three-level dc-dc converters, all of which are very important in photovoltaic applications. Neutral point clamped multilevel inverters in inductive power transfer to achieve load-independent constant current and load-independent constant voltage outputs, fractional order element-based approaches to wireless power transmission, charge balance and pulse charge for lithium iron phosphate batteries, and command of switching dynamics in silicon carbide metal oxide semiconductor field effect transistors are also considered.

A Comprehensive Review on Space Vector Modulation Techniques for Neutral Point Clamped Multi-Level Inverters

The Neutral Point Clamped (NPC) Multi-Level Inverters (MLI) have been ruling the power electronics industries for the past two decades. The Multi-Carrier Pulse Width Modulation (MCPWM) is common PWM techniques which are widely used in NPC-MLI applications. However, MCPWM is not having a good impact on the balancing of DC-link voltages, Common Mode Voltage (CMV) and limiting the Total Harmonics Distortion (THD). The Selective Harmonic Elimination (SHE) technique is introduced for reducing the THD, however all the switching angles should be maintained less than π/2 to keep the eliminated harmonics at constant level which narrows down the modulation index range. Hence, in recent days Space Vector Modulation (SVM) technique is widely used in NPC-MLI, which gives better DC-link voltage balancing, self-neutral point balancing, near-zero CMV reduction, better-quality harmonics profile and switching loss minimization. Hence, it is a preferred solution for the majority of electrical conversion applications such as electric traction, high power industrial drives, renewable power generation, and grid-connected inverters, etc. The paper gives a comprehensive review of the SVM for NPC-MLI. First, this paper deliberates the state of art for two-level SVM and extends it to three-level (3L) SVM. Also compares the 3L SVM performance with other MCPWM techniques. Followed by the various modified MLI SVM techniques in terms of their implementations, DC-link capacitor balancing, and reduction of CMV. Further, the review of MLI SVM is widened to open-end winding Inverters and multiphase MLIs. The final part of this paper discussed the future trends and research directions on MLI SVM techniques and its applications.

Seven Level T-Type Switched Capacitor Inverter Topology for PV Applications

The conventional neutral point clamped (NPC) multilevel inverter topology needs voltage balancing circuits to balance the dc-link capacitor, the number of component count is high and output voltage is half of the input voltage which increase the size of the source side dc/dc converter in PV applications. In this paper, a new topology of seven level neutral point clamped inverter is developed. The proposed inverter has a self-voltage boosting capability using a floating capacitor to boost the output voltage one and half of the input voltage. In this proposed topology, no additional sensors are required for the floating capacitor voltage stability, which results in minimizing the complexity of designing the inverter. The direct link between the neutral point and the mid-point of the dc-link capacitors significantly reduces the leakage current and common mode voltage in this inverter. A thorough comparison between the developed topology and recent suggested topologies is carried out which set the benchmark for the proposed one due to its lower switch count and higher voltage gain. The proposed topology is verified in simulation and prototype hardware model and results are discussed with dynamic load variations. The efficiency of the inverter is 97.1% @200W and low as 88.1 % @ inductive load. The voltage THD is 17.01% for simulation and 19.3% I for experimental is results.

A Hysteresis Space Vector PWM for PV Tied Z-Source NPC-MLI With DC-Link Neutral Point Balancing

The Photo-voltaic (PV) tied Z-source Neutral-point clamped multilevel inverter (Z-NPC-MLI) is used in solar grid connected applications due to its single stage conversion and better performance. Though the Z source inverters adaptation is accepted in grid connected technology, the need for suitable controller and PWM scheme are necessary to meet out the performance such as shoot through switching, neutral point balancing, and harmonic reduction. The space vector pulse width modulation (SVPWM) strategy is a prominent modulation technique for Z-source NPC-MLIs due to the flexibility to select the appropriate voltage vector. Previous publications have shown the control of a Z-source MLI using the SVPWM with and without modification of shoot through switching. However, the current controller (CC) based SVPWM is not matured, which is the most essential consideration for the grid connected inverter to provide neutral point balancing, shoot through control for low harmonic distortion and a high quality current. With all these aims, this paper presents a PV tied Z-NPC-MLI grid connected system with a unique hysteresis current control SVPWM (HSVM) strategy with neutral point (NP) balancing control and direct current control in the inverter input side. Also, the proposed HSVM is assuring the grid connection with high quality voltage and current waveforms. This CC based SVPWM for Z-NPC MLI has been validated through simulation and FPGA based experimental investigations. The results are confirmed the feasibility and reliability of the proposed HSVM for the PV tie grid connected Z- Source NPC-MLI.

Finite control set model predictive control for static synchronous compensator based on hybrid cascaded H‐bridge and neutral point clamped multilevel inverter

Finite control set model predictive control for <scp>static synchronous compensator</scp> based on hybrid cascaded <scp>H‐bridge</scp> and neutral point clamped multilevel inverter

Design and control of a STATCOM based on hybrid cascaded H‐bridge and full‐bridge neutral point clamped multilevel inverter

Design and control of a STATCOM based on hybrid cascaded H‐bridge and full‐bridge neutral point clamped multilevel inverter

Design and implementation of a new unity gain nine‐level active neutral point clamped multilevel inverter topology

Design and implementation of a new unity gain nine‐level active neutral point clamped multilevel inverter topology

Experimental and numerical analysis on SVPWM based grid connected photovoltaic system

Space Vector Pulse Width Modulation (SVPWM) for 3-phase nested neutral point clamped multilevel inverter (NNPC-MLI) which is suitable for grid connected (PV) system is implemented. The use of nested NPC topology helps in increasing the level in output voltage of the inverter. The main task of the system is to balance the flying capacitor voltage using SVPWM, since we have two capacitors in each leg. In this proposed system inverter generates four level in the output voltage, with minimized voltage stress in each switch. Balancing of neutral point voltage is done by redundant inverter switching states. The implementation of modulation technique for voltage balance control is elaborated in detail. Total harmonic distortion (THD) factor in the output is decreased by SVPWM algorithm in this NNPC topology as compared to other inverter topologies. The input for the inverter is taken from PV source and the output is given to grid connected system. Reduction of switching losses is the other added benefit for the nested configuration. The proposed structure is verified using MATLAB/SIMULINK and the simulation results were obtained.