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Measured waveforms from hardware prototype operating as in Fig. 9: ac-coupled upper dc-bus voltage (2 ms/div, 5 V/div) illustrating reduction of third-harmonic ripple voltage (a) without neutral-point regulation and (b) with neutral-point regulation.
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The three-level diode-clamped multilevel converter commonly called the neutral-point-clamped converter has become established to be a preferred topology for high-power motor drive applications operating at several kilovolts. Although solutions to the problem of maintaining a stable neutral-point voltage in the converter continue to be the topic of...
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Citations
... This paper introduces a neutral-point voltage regulator for a three-level diode-clamped multilevel inverter, employing a multiple-carrier sine-triangle modulator and closed-loop control. The proposed approach minimizes voltage distortion and reduces the dc bus capacitance, validated through analytical, simulation, and experimental assessments [5]. D. G, N. R. Varma, A. Spandana, P. A. Kumar, B. Venumadhav, and B. P. Kumar, "Design and Implementation of Three-phase Three Level NPC Inverter," in 2023 7th International Conference on Trends in Electronics and Informatics (ICOEI), Tirunelveli, India: IEEE, Apr. ...
This study delves into the Three-Level Inverter, a notable innovation in power systems known for its enhanced voltage management features in comparison to conventional two-level inverters. By providing more voltage levels, it improves waveform control, which is essential for maintaining stability in the changing global energy environment. The inverter effectively tackles voltage instability concerns by using sophisticated modulation techniques, as shown by oscilloscope analysis and simulation results. The study's implications have a wide range of applications, including solar power systems and electronic device power supply, highlighting its social influence and potential for practical use in energy conversion.
... Refs. [15,16] proposed proportional integral (PI)-based regulation. The control method of the capacitor can suppress the DC voltage deviation and reduce the low-frequency fluctuation through PI parameter matching, but the instantaneous control effect of voltage balancing regulation is weakened when the load changes. ...
Three-level neutral-point clamped (NPC) inverters are widely used in the new energy power generation, motor drive, and many other occasions. However, the neutral-point voltage imbalance of an NPC inverter will affect the output of the inverter system, and the control of the neutral point voltage has become a popular research topic. In this paper, a compensation-voltage-injection-based neutral-point voltage balancing method is proposed. During the switching cycle, the average value model of the neutral-point current under different voltage vectors is applied to calculate the value of the compensation voltage that needs to be injected. The self-balance of the neutral-point voltage based on a switching cycle is realized, and the influence of modulation ratio and power factor on equalization ability is discussed. A MATLAB/Simulink simulation model and a small power prototype are established to verify the effectiveness of the method, and the simulation and experimental results show that the proposed method can effectively suppress the neutral-point voltage fluctuation in a wide range of modulation ratios and power factors.
... Multi-level inverter topologies such as neutral point clamped (3 level NPC) have a split DC bus. Under normal conditions, DC balance control [8] is used to equal the voltage on each section of the DC bus. An unbalance above a threshold indicates a mis-operation of the inverter and necessitates a trip. ...
p>Trips of inverter-based resources (IBR) have been observed more commonly during grid disturbance events in power systems. Such events have caused concerns due to the high penetration of IBRs and the magnitude of recent trip events. Inverter trips could potentially compromise system reliability due to loss of generation from resources. In this work, some major causes of inverter trips are explained and the root cause behind these trips are analyzed. While the performance of the inverter can vary with manufacturer, there are some underlying aspects of these trips that could be common to the industry. The link between the trips and resource behavior, physical limits and grid requirements are analyzed. Some approaches to mitigate such trips are proposed and simulation results are presented to validate the approach. The approaches proposed are deemed low risk since the changes proposed are rather simplistic and reduce the risk of inverter reaching a physical limit during grid disturbances. </p
... Multi-level inverter topologies such as neutral point clamped (3 level NPC) have a split DC bus. Under normal conditions, DC balance control [8] is used to equal the voltage on each section of the DC bus. An unbalance above a threshold indicates a mis-operation of the inverter and necessitates a trip. ...
p>Trips of inverter-based resources (IBR) have been observed more commonly during grid disturbance events in power systems. Such events have caused concerns due to the high penetration of IBRs and the magnitude of recent trip events. Inverter trips could potentially compromise system reliability due to loss of generation from resources. In this work, some major causes of inverter trips are explained and the root cause behind these trips are analyzed. While the performance of the inverter can vary with manufacturer, there are some underlying aspects of these trips that could be common to the industry. The link between the trips and resource behavior, physical limits and grid requirements are analyzed. Some approaches to mitigate such trips are proposed and simulation results are presented to validate the approach. The approaches proposed are deemed low risk since the changes proposed are rather simplistic and reduce the risk of inverter reaching a physical limit during grid disturbances. </p
... The dc voltage deviation will reduce the effect of the filter on CMV suppression. In multilevel inverters, main balancing approaches are the use of auxiliary balancing networks [23], [29] and the control of redundant switch states [30]- [32]. Due to the different reasons of the dc voltage deviation and the different circuit structures, the voltage balancing method used in multilevel inverters cannot be used in active filters. ...
In three-phase inverters, high output common-mode voltage (CMV) will bring many negative effects. The active filter with a capacitive voltage divider (CVD) can effectively suppress the peaks of CMV both in the time-domain and frequency-domain. In practice, it is found that the dc voltage of active filter from the CVD will deviate. In this paper, it is found that the deviation comes from the switching dead-time of the active filter. Based on the study in regard to the influence of switching dead-time on the dc voltage of CVD, a variable switching dead-time (VSDT) scheme is proposed. The VSDT scheme can make the voltage of CVD approach the ideal voltage and lead the maximum spectral peak of the CMV to the lowest. The feasibility and effectiveness of the VSDT scheme are verified by the simulations and experiments in a three-phase inverter.
... T is the inverter current vector and C dc = C 1 = C 2 . The transfer function of this neutral-point potential with respect to compensation signal d v is a nonlinear expression with a complex structure, where a complete analysis for NPC converters is reported in [37]. However, the main dependence of this variable is the capacitor voltage dynamic. ...
An important requirement of the power grid with high penetration of renewable energy sources is the mitigation of potential harmonic interactions between different distributed large grid-tie inverters and the mains. This work presents the harmonic interaction between multiple multilevel photovoltaic (PV) inverters based on the well-known T-type neutral-point-clamped inverter (3L-TNPC). The multiple 3L-TNPC is connected in parallel to a common ac bus by using distribution voltage feeders. The analysis is performed by using the Norton equivalence model of each power circuit, its admittance matrix modeling, and the potential overall impedance resonances with the ac grid. The main contribution of this work is the development of a current harmonic injection model of the system operating under a polluted voltage grid for harmonic analysis, while overall filtering design restrictions due to impedance limits based on current and voltage standards are considered. The proposed impedance Norton model is compared with the electromagnetic transient model (EMT model) by using comprehensive simulations, showing good match between both models.
... Furthermore, DC-link voltage balance is another important point in a three-level converter. Control algorithm should be adopted to guarantee the voltage balance of neutral point [27]. e difference between u dc1 and u dc2 should be considered to eliminate its negative impact on the power quality, especially for even-order harmonic performance of PCS. ...
Finite control set model predictive control (FCSMPC) is a highly attractive and potential control method for grid-tied converters. However, there are several challenges when employing FCSMPC in an LCL filter-based T-type three-level power conversion system (PCS) for battery energy storage applications. These challenges mainly include the increasing complexity of control algorithm and excessive cost of additional sensors, which deteriorate the performance of PCS and limit the application of FCSMPC. In order to overcome these issues, this paper proposes a simplified FCSMPC algorithm to reduce the computation complexity. Furthermore, full-dimensional state observers are adopted and implemented to estimate the instantaneous values of grid-side current and capacitor voltage for purpose of removing unnecessary electrical sensors. The implementation of proposed FCSMPC algorithm is described step by step in detail. Simulation results are provided as a verification for the correctness of theoretical analysis. Finally, a three-phase T-type three-level PCS prototype rated at 2.30 kVA/110 V is built up. Experimental results extracted from the prototype can verify the effectiveness of the proposed control strategy.
... where N balance needs to be selected to produce a sufficiently fast capacitor voltage balancing response without imposing high switching loss. Although the bandwidths of neutral point voltage balancing control grid-connected DC/AC multi-level inverters are usually at the magnitude of hundred Hz [17] to mitigate the third order harmonic injection, it is not necessary to have such high bandwidths in DC/DC converters. In this paper, N balance = 1000 is used with a switching frequency of 20kHz, which produces a bandwidth of 20Hz for capacitor voltage balancing. ...
In order to reduce the volume, weight and cost of conventional hybrid energy storage system (HESS) while properly exploring the complementary features of different energy storage devices for DC microgrid applications, this paper proposes a multiple‐port three‐level DC/DC converter. It possesses multiple ports sharing one front‐end three‐level DC/DC converter with an inductor and supercapacitor bank. Different types of batteries and/or multiple battery banks can be interfaced through the multiple terminals. Such a converter structure facilitates the cooperation of different energy storage devices to satisfy various power demands of DC microgrids with intermittent renewable generation plants. Moreover, the proposed structure allows power sharing among different energy storage devices, which enables more efficient cooperation of different battery banks or different types of batteries. Experimental results are presented to verify the efficacy of the proposed converter structure and its control.
... This dictates that, industries pays more attention on the application of AC drives in support of various power electronic based control topologies in cost effective mode. In order to meet the required demand in industrial applications, it is necessary to switch high power voltage applications of the AC drives [1]- [4]. Also, it is necessary to obtain the operation of these AC drives at high power voltage applications industries in cost effective with high efficiency and reliable. ...
... Many researchers are proposed modular multilevel converters (MMC) for medium to high power voltage AC drive applications with their own control strategies to obtain the efficient performance of variable AC drives. Multilevel converters such as neutral point clamped converter [1] and flying capacitor converter [2] are employed to AC drive applications to obtain lower dv/dt stresses and harmonics in output voltages. But these converters are limited to number of levels only [3]. ...
Variable speed drive applications in the industrial vicinity playing a vital role in nation development. The majority of the industries are engaged with AC induction machine drives due to easy, smooth and reliable drive operations for its various variable drive applications. Recent advances in power electronic technologies makes the efficient control schemes to obtain a smooth and reliable variable speed drives. Modular multilevel converter (MMC) technique plays a significant role in applications of high power rating such as HVDC. The application of these modular multilevel converter techniques now extended to various variable induction machine speed drive applications in industrial services due to its superior benefits of investment and life cycle cost. Modular multilevel converters designed in number of modules to obtain ripple and harmonic less voltage out puts of the induction machines. Different topologies and control strategies of modular multilevel converters are observed and employed by the various researchers elsewhere in the world. This paper presets a novel review on applications of modular multilevel converters used in different drive applications. Also, this paper presents a detail review on different topologies and control schemes used elsewhere in the world and made suggestion on application of efficient modular multilevel converter technique configuration to obtain effective performance of induction machine at different drive applications
... Inverters is divided into two parts according to the dependence of its sources, the one that depends on the source of the voltage in general (divided into three new sections: a flying capacitor inverter [1], a diode clamp inverter [2,3], and a cascade H bridge inverter [4][5][6]), and another that depends on the current source [7]. ...
Many industries used multilevel inverter in high-voltage applications, this transformer attains many merits
such power factor rectification, product voltage arranging from power transmission and reduction of overall harmonic
distortions with a two-level inverter installed. As the numeral of planes growing, producing waveform which
has more steps, resulting in a sine wave that oncoming very closely to the in-demand wave, so the waveforms with
higher quality as THD approaches zero (reducing harmonics her the harmonic deformation rate of single-phase
from three -thirteen (three, five, seven, nine, eleven and thirteen) level AC-DC converter will be presented.
