Width Modulation Research Articles

Experimental Study on Seismic Performance of Kancingan Timber Frame Infill Walls Building

This study was carried out to examine the seismic performance of Kancingan house walls and the behavior of their timber frames, brick infill, and anchor nails during cyclic loading tests. Kancingan House, a timber frame building with brick infill walls, is a cost-effective and efficient method of wall construction commonly used in houses in Merauke, Indonesia. The experimental method was used to determine the seismic performance of the walls built using buswood with a module width of 100 cm and a height of 130 cm through cyclic load testing. The result showed a maximum lateral load of 26.43 kN with a displacement of 19.08 mm under compression loading and 28.78 kN under tensile loading with 15.6 mm displacement. The initial stiffness was measured at 5.03 kN and 9.59 kN/mm for compressive and tensile loading, respectively. Furthermore, ultimate load and displacement of 21.14 kN and 23.02 kN were obtained at a displacement of 30.68 mm under compressive loading and 25.23 mm under tensile loading. The ductility values of 10.76 and 9.78 were obtained under compressive and tensile loading. In conclusion, the study found that each wall element supports the seismic performance of the structure. As opposed to the timber frame, the infill walls have not suffered much damage except a hair crack because of the presence of anchor nails that keep the infill wall from collapsing when it loses its bond with the timber frames. Doi: 10.28991/CEJ-2024-010-08-06 Full Text: PDF

Existence of edge modes in periodic microstrip transmission line

The microstrip of modulated width is a realization of a one-dimensional photonic crystal operating in the microwave regime. Like any photonic crystal, the periodic microstrip is characterised by the presence of frequency bands and band gaps that enable and prohibit wave propagation, respectively. The frequency bands for microstrip of the symmetric unit cell can be distinguished by 0 or π\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\pi$$\\end{document} Zak phase. The sum of these topological parameters for all bands below a given frequency gap determines the value of the surface impedance at the end of the microstrip. We demonstrate that edge modes are absent in a finite microstrip terminated at both ends in the centres of unit cells, but they can be induced by adding the defected cells. Edge modes present at both ends of the microstrip enable microwave tunneling with high transitivity in the frequency gap with or without a change in phase. This has been demonstrated experimentally and developed in detail using numerical simulations and model calculations. The investigated system, with a doublet of edge modes in the frequency gap, can be considered as a narrow passband filter of high selectivity and characterised by a significant group delay.

An Experimental Investigation on VSI-fed Induction Motor using Xilinx ZYNQ-7000 SoC Controller

In medium voltage and high-power drive applications, pulse width modulation (PWM) techniques are widely used to achieve effective speed control of AC motors. In real-time, an industrial drive system requires reduced hardware complexity and low computation time. The reliability of the AC drive can be improved with the FPGA (field programmable gate array) hardware equipped with digital controllers. To improve the performance of AC drives, a new FPGA-based Wavect real-time prototype controller (Xilinx ZYNQ-7000 SoC) is used to verify the effectiveness of the controller. These advanced controllers are capable of reducing computation time and enhancing the drive performance in real-time applications. The comparative performance analysis is carried out for the most commonly used voltage source inverter (VSI)-based PWM techniques such as sinusoidal pulse width modulation (SPWM) and space vector pulse width modulation (SVPWM) for three-phase, two-level inverters. The comparative study shows the SVPWM technique utilizes DC bus voltage more effectively and produces less harmonic distortion in terms of higher output voltage, flexible control of output frequency, and reduced harmonic distortion at output voltage for motor control applications. The simulation and hardware results are verified and validated by using MATLAB/Simulink software and FPGA-based Wavect real-time controller respectively.

LVRT Enhancement of DFIG-based WECS using SVPWM-based Inverter Control

Abstract: Across many countries, wind turbine generation systems (WTGS) have been established over the past few decades. In this paper, we augment the low voltage ride-through (LVRT) enrichment facility of driving a DFIG-based wind energy conversion system (WECS) using space vector pulse width modulation (SVPWM)-based inverter control. The proposed technique employs an SVPWM-based control algorithm to regulate the voltage and frequency of the output power during grid faults, thereby enhancing the WECS's ability to remain connected to the grid and provide power. The study focuses on decreasing transient current throughout the instant of fault. Modeling and control approaches were also discussed in this study. The performance of the proposed technique is evaluated using MATLAB/Simulink simulations, and the results demonstrate that the technique effectively improves the LVRT capability of the DFIG-based WECS. Background: Due to the variation in wind speed, the power generated by wind turbines is inconsistent. The power generated and the losses in wind turbines change correspondingly with changes in wind speed. The only type of machine that can generate power at speeds below the fixed speed is the doubly-fed induction generator (DFIG). But DFIG is oversensitive to network faults, which makes the bidirectional converters and DC link capacitor fail due to high inrush current and over-voltage. Methods: The converters connected to DFIG consist of an AC-to-DC converter, a boost converter, and a space vector pulse width modulation (SVPWM)-based DC-AC converter. The performance of the SVPWM controller is analyzed during symmetrical and unsymmetrical fault conditions. Results: The anticipated control provides adequate reactive power support to the network through the time of the fault and improves voltage and current waveform. The reactive power flow is also analyzed, and the effectiveness of the proposed controller is verified using MATLAB and Simulink. Conclusion: SVPWM (Space Vector Pulse Width Modulation)-based inverter control is an effective technique for wind energy conversion systems (WECS). The use of SVPWM can provide accurate and precise control of the AC voltage generated from the DC voltage source, resulting in improved system efficiency and reduced harmonic distortion in the output waveform. : The comparative analysis of THD suggests that SVPWM is a superior technique compared to other inverter control techniques such as sine-triangle pulse width modulation (SPWM) and carrier-based pulse width modulation (CPWM). SVPWM can help to reduce the distortion in the output waveform, leading to improved system efficiency, reduced wear on the system components, and overall better performance of the WECS. Furthermore, SVPWM offers several advantages over other inverter control techniques, including better utilization of DC voltage, improved voltage control, and better utilization of switching devices. These advantages make SVPWM a valuable tool for optimizing the operation of WECS and improving the reliability and performance of renewable energy systems. The value of THD for SVPWM inverter control in WECS is 1.53 under symmetrical fault and 1.34 for unsymmetrical fault, respectively. In summary, the use of SVPWM-based inverter control for WECS is an effective way to improve the efficiency and performance of the system while reducing the distortion in the output waveform and providing adequate reactive power support. The advantages of SVPWM over other inverter control techniques make it a valuable tool for the development and optimization of renewable energy systems.

A driving method for gray scale multiplication of electrowetting display based on hybrid modulation

In order to solve the problem of low gray level due to the few driving chips developed based on the photoelectric characteristics of electrowetting display, a driving method based on modulation is proposed to double the gray level of electrowetting display. In this method, the driving waveform based on pulse amplitude modulation and pulse width modulation hybrid modulation is designed, and the gray level–luminance curve of the electrowetting display is measured and analyzed. On this basis, the luminance nonlinear correction is carried out, and the improvement of 64 Gy levels to 127 Gy levels is realized by the principle of human visual persistence phenomenon. The experimental results show that the proposed driving scheme can break through the limitation of the driving chip and realize the multiplication of gray levels, in which 96% gray levels increase steadily with an average luminance difference of 0.07, and at the same time enhance the contrast and improve the display effect.

Investigation of magnetization dynamics in trilayer width-modulated nanowires

We have investigated the magnetization reversal processes and dynamic behavior of trilayered Py(50 nm)/Pd(tPd)/Py(20 nm) nanowires with periodic width modulation as a function of spacer layer thickness tPd in the range from 0 to 10 nm and compared them with single-layer nanowires. The ferromagnetic resonance spectra show more than three modes that result from a non-uniform demagnetizing field in width-modulated nanowires. We observe that the spacer layer thickness influenced the ferromagnetic resonance spectra, which showed different numbers and values of modes and frequencies due to the different magnetization configurations for different spacer layer thicknesses. We also found that the two ferromagnetic layers are exchange-coupled for tPd = 2 nm nanowire arrays, showing the sharp switching of magnetization from the static measurements and sharp frequency jump from 13.6 to 14.7 GHz around −18 mT from the dynamic measurements. However, for tPd = 10 nm, the two layers switch at different fields, indicating a gradual decrease in magnetization as the reversal is mediated through dipolar coupling. The origin of modes is well explained from the spatial mode profiles of top and bottom magnetic layers. The dynamic responses in this spin-valve-type structure are useful for designing microwave-based spintronic devices.

Comparative Study of Advanced Modulation and Control Schemes for Dual Three-Phase PMSM Drives With Low Switching Frequencies

In this paper, multiple advanced low-switching-frequency modulation and control schemes are investigated for dual three-phase permanent-magnet synchronous motor (PMSM) drives. The modulation schemes under investigation include multisampling space vector modulation (MS-SVM), selective harmonic elimination pulse width modulation (SHEPWM) and synchronous optimal pulse width modulation (SOPWM) while the control schemes include complex vector control, model predictive control (MPC) and flux trajectory control-based model predictive pulse pattern control (MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C). The difference between three-phase and dual three-phase PMSM drives at low switching frequencies is analyzed. Moreover, an optimal pulse width modulation (PWM)-based MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C scheme is proposed for the dual three-phase PMSM, where the optimal PWM modulation and MP <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> C control are combined such that the optimal steady-state and dynamic control performance is achieved among the modulation and control schemes investigated. Experimental results are given to compare and validate the proposed control scheme.

A generalized model for monitor units determination in ocular proton therapy using machine learning: A proof-of-concept study

Objective. Determining and verifying the number of monitor units is crucial to achieving the desired dose distribution in radiotherapy and maintaining treatment efficacy. However, current commercial treatment planning system(s) dedicated to ocular passive eyelines in proton therapy do not provide the number of monitor units for patient-specific plan delivery. Performing specific pre-treatment field measurements, which is time and resource consuming, is usually gold-standard practice. This proof-of-concept study reports on the development of a multi-institutional-based generalized model for monitor units determination in proton therapy for eye melanoma treatments. Approach. To cope with the small number of patients being treated in proton centers, three European institutes participated in this study. Measurements data were collected to address output factor differences across the institutes, especially as function of field size, spread-out Bragg peak modulation width, residual range, and air gap. A generic model for monitor units prediction using a large number of 3748 patients and broad diversity in tumor patterns, was evaluated using six popular machine learning algorithms: (i) decision tree; (ii) random forest, (iii) extra trees, (iv) K-nearest neighbors, (v) gradient boosting, and (vi) the support vector regression. Features used as inputs into each machine learning pipeline were: Spread-out Bragg peak width, range, air gap, fraction and calibration doses. Performance measure was scored using the mean absolute error, which was the difference between predicted and real monitor units, as collected from institutional gold-standard methods. Main results. Predictions across algorithms were accurate within 3% uncertainty for up to 85.2% of the plans and within 10% uncertainty for up to 98.6% of the plans with the extra trees algorithm. Significance. A proof-of-concept of using machine learning-based generic monitor units determination in ocular proton therapy has been demonstrated. This could trigger the development of an independent monitor units calculation tool for clinical use.

A High-Capacity Interleaved Parallel Full-Bridge LLC Converter for External Charging Applications

This paper explores innovative converter designs tailored to meet the evolving demands of modern electric vehicle (EV) charging and power conversion systems. The first investigation centres on an AC to DC converter featuring an input series inductor and an output capacitor, enhancing power factor correction, reducing harmonics, and optimizing voltage regulation through advanced simulation tools. Comparative analysis highlights its superior power factor maintenance and efficiency. The second proposal introduces an interleaved parallel LLC (Inductor-Inductor-Capacitor) DC/DC converter, incorporating hybrid pulse frequency modulation (PFM) and pulse width modulation (PWM) control. This design extends the adjustable output voltage range, ensuring precise voltage control. A meticulous analysis and parametric design demonstrate an output voltage range of 50–80 V and a maximum power of 20 kW through simulation results. These innovations hold promise for various applications, including renewable energy, electronic device power supplies, and EV charging, offering practical solutions to enhance energy efficiency and power quality across modern electrical systems and EV infrastructure.

Switched capacitor based 7-level and 9-level multilevel inverters with single DC source and reduced voltage stress

This paper proposes two different switched capacitor based Multilevel Inverter topologies having single dc voltage source. One of the proposed MLIs is a seven-level structure whereas the other circuit successfully generates a nine-level output voltage. The special features of the seven-level topology consist of reduced number of circuit elements, lower voltage stress on switches, and boosted output voltage. The nine-level MLI having unity gain also possess the reduced switch count along with lower value of switch voltage stress. Fundamental frequency based Nearest Level Control modulation and Level-Shifted Pulse Width Modulation have been used for generating the required voltage levels. Successful implementation of the proposed MLI circuits has been done with the help of a laboratory prototype and its results are presented and explained in the paper to show its practical suitability. Other type of analysis include loss analysis which has been done in PLECS software. From this analysis, the efficiency has been estimated. A comparative analysis of both the proposed structures has been carried out with some other similar topologies on different performance parameters. From the analysis and comparison, it is evident that the proposed MLIs are better than some of the existing topologies and can be used for industrial applications.

Error performance analysis for chaotic pulse width position modulation in free space optical communication system

Abstract In this paper, a pulse time modulation method called chaotic pulse width position modulation (CPWPM) is studied for free space optical communication system. This is a digital modulation technique that combines pulse position modulation and pulse width modulation with chaos. In this scheme, the binary information is carried by both the position and width of the pulses, which are modulated by a chaotic signal. Hence, on a single pulse, two bits of information are encoded, which results in higher bit rates, better privacy, and larger effective bandwidth as compared to chaotic pulse position modulation (CPPM) and chaotic pulse width modulation (CPWM) techniques. Probability of error is investigated for different FSO scenarios, i.e., varying turbulence conditions and link lengths for CPWPM scheme. Finally, the performance of CPWPM-FSO system is compared with a commonly used differential chaos shift keying (DCSK) scheme. CPWPM-FSO system shows comparable results as DCSK-FSO system (for probability of error, P e = 10−4 average signal-to-noise ratio (SNR) required for DCSK and CPWPM scheme is 40 dB and 41 dB, respectively, for same length and system conditions), while data rate is doubled in latter, and this verifies the validity of using CPWPM in FSO communication system.

Gate‐Last MoS2 Transistors for Active‐Matrix Display Driving Circuits

AbstractAdvancements in display technology have primarily focused on discovering new materials to develop thin‐film transistors (TFTs) that complement mainstream technologies. The emerging 2D semiconductors are one of the most promising candidates due to their ultra‐thin thickness, exceptional electrical qualities, and large‐scale availability. However, these atomically thin materials are delicate and typically prepared through standard gate‐first fabrication processes, necessitating their transfer onto specific substrates. In this study, a demonstration of an in situ gate‐last process for 2D semiconductor‐based TFTs technology is presented. This approach bypasses the yield‐limiting transfer process, enabling large‐scale display applications. The as‐fabricated MoS2 TFTs retains their intrinsic properties with a current density reaching ≈≈10 µA µm−1. Additionally, it is successfully showcased that the two transistor‐one capacitor active‐matrix display driving circuits with a high pixel yield. The patterned matrix exhibits no crosstalk and can be driven by either the pulse amplitude modulation or pulse width modulation scheme, offering flexible applications.

Non-Isolated Current-Fed Series Resonant Converter with Hybrid Control Algorithms for DC Microgrid

Module-level power electronics can optimize the power generation of photovoltaic panels, which requires a simple topology structure, high power conversion efficiency, and wide voltage gain, corresponding to irradiance variations. This paper proposes a non-isolated current-fed L-C series resonant converter and its control algorithms. The proposed converter can obtain a buck–boost voltage gain with the hybrid control algorithm utilizing the switching frequency modulation and asymmetric pulse width modulation. The proper power stage design can guarantee the soft-switching capability for the entire operating range. Also, the control strategy is designed to obtain a small rms current. The operational principle of proposed converter is analyzed in order to design the resonant tank and control strategy. The performance of designed converter can be verified with the experimental results with a 500 W prototype converter.

Pulse‐Modulation Controllable Monolithic Full‐Color Semipolar GaN‐based Light Emitting Diodes

AbstractMonolithic multi‐color light‐emitting diodes (LEDs) offer numerous advantages as multi‐functional lighting sources. However, the achievement of full‐color monolithic LEDs spanning from red to blue wavelengths is limited by the InN‐GaN material system. To overcome this limitation, this work demonstrates a new approach using hexagonal epitaxial lateral overgrowth to reduce the density of crystal defects and form micro‐surface structures. By utilizing arrowhead‐like surfaces in semipolar GaN films, indium incorporation can be controlled, leading to larger band‐filling effects and enabling full‐color red, green, and blue emissions from a single LED. Nonetheless, the red emission in monolithic full‐color LEDs is weaker than the blue emission due to the band‐filling induced blueshift that occurs with increasing current injection. To address this issue, pulse amplitude modulation and pulse width modulation modes are introduced to control the emission intensity from red to blue wavelengths. As a result, the study achieves a monolithic trichromatic white LED with color coordinates of (0.2985, 0.3948) and a color temperature of ≈6700 K by simultaneously emitting red, green, and blue LEDs with the same emission intensities. This achievement holds great promise for the development of high‐performance full‐color LEDs for multifunctional lighting sources that can span red, green, and blue wavelengths.

Excitation and quasi-transition of rogue waves in a one-dimensional quantum droplet

We study the dynamics of rogue wave excitations and quasi-transitions in one-dimensional quantum droplets, whose homogeneous-density flat top provides an applicable background wave for nonlinear excitation. Using a quenching technique and a localized space modulation technique for the nonlinear effect coefficient, the rogue wave is excited on droplets. The excitation modes of rogue waves can be transitioned to dispersive shock waves or Kuznetsov–Ma breathers by regulating their modulation amplitude and width, and their maximal density and width can be regulated by modulation their amplitude. Meanwhile, two Gaussian modulations for droplets also bring the second-order rogue wave’s dynamics, whose maximal amplitude can approach 3.6 times that of the amplitude of droplets. Our results provide guidance for rogue wave excitation and transition on self-bound background waves and deepen our understanding of quantum droplets.

Design and Performance Analysis of New Multilevel Inverter for PV System

Multilevel inverters (MLIs) have recently attracted more attention in medium-voltage and high-power applications as they can provide an effective interface with photovoltaic (PV) systems. Conventional MLIs are used to generate higher voltage levels, which improve power quality and reduce the requirement for passive filters. However, recent research has focused on designing new MLI topologies using reduced switch counts and less voltage stress. This study, as such, proposes a new nine-level symmetric MLI for PV systems with a minimum number of switches. This decrease in the number of switches reduces the voltage stress across the switches and the number of driving circuits, which lowers the complexity of the control circuit and, as a result, lowers the cost and size of the system. This article compares the proposed MLI with other topologies based on the DC sources, switches count, gate driver circuits (Ngd), total standing voltage per unit (TSVPU), cost function (CF), and components count per level (CC/L). The proposed topology is integrated with the PV system. MATLAB software is used to evaluate the performance of MLI at step change in irradiance and under variable load conditions. The total harmonic distortion (THD) of the proposed topology is reduced with the implementation of phase disposition pulse width modulation (PD-PWM). In addition, PD-PWM is compared with phase opposition disposition pulse width modulation (POD-PWM) and alternative phase opposition disposition pulse width (APOD-PWM) modulation techniques. The simulation results reveal the improved performance of the proposed topology at variable irradiance and under varying load conditions. The comparison results reveal minimum (TSVPU), CC/L, CF, and switch count compared to existing topologies. Hence, the proposed topology of MLI is cost-effective and superior in all aspects compared to other topologies. In summary, it offers overall improved performance, and thus, it is feasible for the PV system.

Mitigation of harmonics for five level multilevel inverter with fuzzy logic controller

Introduction. The advantages of a high-power quality waveform and a high voltage capability of multilevel inverters have made them increasingly popular in recent years. These inverters reduce harmonic distortion and improve the voltage output. Realistically speaking, as the number of voltage levels increases, so does the quality of the multilevel output-voltage waveform. When it comes to industrial power converters, these inverters are by far the most critical. Novelty. Multilevel cascade inverters can be used to convert multiple direct current sources into one direct current. These inverters have been getting a lot of attention recently for high-power applications. A cascade H-bridge multilevel inverter controller is proposed in this paper. A change in the pulse width of selective pulse width modulation modulates the output of the multilevel cascade inverter. Purpose. The total harmonic distortion can be reduced by using filters on controllers like PI and fuzzy logic controllers. Methods. The proposed topology is implemented with MATLAB/Simulink, using gating pulses and pulse width modulation methodology and fuzzy logic controllers. Moreover, the proposed model also has been validated and compared to the hardware system. Results. Total harmonic distortion, number of power switches, output voltage and number of DC sources are analyzed with conventional topologies. Practical value. The proposed topology has been very supportive for implementing photovoltaic based multilevel inverter, which is connected to large demand in grid and industry.

Comparison of DC Motor Speed Calculation Efficiency between Inductive Proximity Sensor and Rotary Encoder

This study examines the level of effectiveness and efficiency of a sensor on the calculation of the rotational speed (RPM) of a DC motor, considering that the calculation of the rotational speed of an electric motor, both AC motors and DC motors, greatly influences the output of the system. the speed of motor rotation is very influential in several fields, such as power generation, which will affect the output voltage that will be generated. There are many methods for measuring the rotational speed of a motor, including using an inductive proximity sensor and a rotary encoder combined with a PLC as a control center and data processor so that the rotational speed can be read. the output of the proximity sensor and rotary encoder will be connected to the PLC input pin so that data will appear in the form of a pulse value which can be seen in the program that has been made. The data obtained will be processed in a program that uses special instructions, namely PRV. In comparison, the speed of a dc motor will be changed using a PWM module or pulse width modulation to adjust the rotational speed of the motor. From the results of experiments that have been carried out using the proximity sensor, it gives an average motor speed reading of 6420 Rpm with an error of -10.3, and experiments carried out using a rotary encoder give an average motor speed reading of 6409.3 Rpm with an error of 0.4 so that it can be concluded that the use of a rotary encoder is more accurate than the use of a proximity sensor to calculate motor speed.

Double scattering and pencil beam scanning Monte Carlo workflows for proton therapy retrospective studies on radiation-induced toxicities

PurposeMonte Carlo (MC) simulations can be used to accurately simulate dose and linear energy transfers (LET) distributions, thereby allowing for the calculation of the relative biological effectiveness (RBE) of protons. We present hereby the validation and implementation of a workflow for the Monte Carlo modelling of the double scattered and pencil beam scanning proton beamlines at our institution. MethodsThe TOPAS/Geant4 MC model of the clinical nozzle has been comprehensively validated against measurements. The validation also included a comparison between simulated clinical treatment plans for four representative patients and the clinical treatment planning system (TPS). Moreover, an in-house tool implemented in Python was tested to assess the variable RBE-weighted dose in proton plans, which was illustrated for a patient case with a developing radiation-induced toxicity. ResultsThe simulated range and modulation width closely matches the measurements. Gamma-indexes (3%/3mm 3D), which compare the TPS and MC computations, showed a passing rate superior to 98%. The calculated RBE-weighted dose presented a slight increase at the necrosis location, within the PTV margins. This indicates the need for reporting on the physical and biological effects of irradiation in high dose regions, especially at the healthy tissues and increased LET distributions location. ConclusionThe results demonstrate that the Monte Carlo method can be used to independently validate a TPS calculation, and to estimate LET distributions. The features of the in-house tool can be used to correlate LET and RBE-weighted dose distributions with the incidence of radiation-induced toxicities following proton therapy treatments.

Topology and Modulation of Fractional-Level MMC for DC Distribution Grids

For the modular multilevel converter (MMC) with a small quantity of submodules, neither nearest level modulation (NLM) nor carrier phase-shifted pulse width modulation (CPS-PWM) can achieve high voltage quality and low operation loss simultaneously. In this paper, a novel fractional-level MMC (FLMMC) topology is proposed, in which fractional-level submodules are introduced to multiply the output levels. To balance the capacitor voltages between conventional submodules and fractional-level submodules, this paper develops a fractional-level modulation (FLM) method suitable for FLMMC. Considering control complexity and device quantity, the FLMMC with two half-level or one-third-level submodules in each arm is investigated in this paper. Simulation and experiment tests are carried out to validate the effectiveness and superiority of FLMMC under FLM. FLMMC can improve the voltage quality without increasing control complexity, circulating current and switching loss, so as to comprehensively adapt to the power quality requirements of dc distribution grids.