• Title, Summary, Keyword: Multilevel converters

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Asymmetric Cascaded Multi-level Inverter: A Solution to Obtain High Number of Voltage Levels

  • Banaei, M.R.;Salary, E.
    • Journal of Electrical Engineering and Technology
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    • v.8 no.2
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    • pp.316-325
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    • 2013
  • Multilevel inverters produce a staircase output voltage from DC voltage sources. Requiring great number of semiconductor switches is main disadvantage of multilevel inverters. The multilevel inverters can be divided in two groups: symmetric and asymmetric converters. The asymmetric multilevel inverters provide a large number of output steps without increasing the number of DC voltage sources and components. In this paper, a novel topology for multilevel converters is proposed using cascaded sub-multilevel Cells. This sub-multilevel converters can produce five levels of voltage. Four algorithms for determining the DC voltage sources magnitudes have been presented. Finally, in order to verify the theoretical issues, simulation is presented.

Optimal Topologies for Cascaded Sub-Multilevel Converters

  • Babaei, Ebrahim
    • Journal of Power Electronics
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    • v.10 no.3
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    • pp.251-261
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    • 2010
  • The general function of a multilevel converter is to synthesize a desired output voltage from several levels of dc voltages as inputs. In order to increase the steps in the output voltage, a new topology is recommended in [1], which benefits from a series connection of sub-multilevel converters. In the procedure described in this reference, despite all the advantages, it is not possible to produce all the steps (odd and even) in the output. In addition, for producing an output voltage with a constant number of steps, there are different configurations with a different number of components. In this paper, the optimal structures for this topology are investigated for various objectives such as minimum number of switches and dc voltage sources and minimum standing voltage on the switches for producing the maximum output voltage steps. Two new algorithms for determining the dc voltage sources magnitudes have been proposed. Finally, in order to verify the theoretical issues, simulation and experimental results for a 49-level converter with a maximum output voltage of 200V are presented.

Advanced Cascade Multilevel Converter with Reduction in Number of Components

  • Ajami, Ali;Oskuee, Mohammad Reza Jannati;Mokhberdoran, Ataollah;Khosroshahi, Mahdi Toupchi
    • Journal of Electrical Engineering and Technology
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    • v.9 no.1
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    • pp.127-135
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    • 2014
  • In this paper a novel converter structure based on cascade converter family is presented. The suggested multilevel advanced cascade converter has benefits such as reduction in number of switches and power losses. Comparison depict that proposed topology has the least number of IGBTs among all multilevel cascade type converters which have been introduced recently. This characteristic causes low cost and small installation area for suggested converter. The number of on state switches in current path is less than conventional topologies and so the output voltage drop and power losses are decreased. Symmetric and asymmetric modes are analyzed and compared with conventional multilevel cascade converter. Simulation and experimental results are presented to illustrate validity, good performance and effectiveness of the proposed configuration. The suggested converter can be applied in medium/high voltage and PV applications.

A Pulsed Mode Operating DC Power Supply Based on Modified Multilevel Converter (Modified 멀티레벨 컨버터 기반 펄스모드 동작 직류전원장치)

  • Ahn J.S.;Nho E.C.;Kim I.D.;Kim H.G.;Chun T.W.
    • Proceedings of the KIPE Conference
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    • pp.264-268
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    • 2003
  • This paper describes a high voltage high power DC power supply which has the ability of pulsed mode operation. The power supply Is constructed with several series connected power converters based on modified multilevel converters. The modified multilevel converters are suitable for the protection of frequent output short-circuit. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there is no overshoot of the do voltage because the dc output capacitors keep undischarged state. Analysis, simulations, and experiments are carried out to Investigate the operation and usefulness of the proposed scheme.

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A Novel Analytical Method for Selective Harmonic Elimination Problem in Five-Level Converters

  • Golshan, Farzad;Abrishamifar, Adib;Arasteh, Mohammad
    • Journal of Power Electronics
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    • v.17 no.4
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    • pp.914-922
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    • 2017
  • Multilevel converters have attracted a lot of attention in recent years. The efficiency parameters of a multilevel converter such as the switching losses and total harmonic distortion (THD) mainly depend on the modulation strategy used to control the converter. Among all of the modulation techniques, the selective harmonic elimination (SHE) method is particularly suitable for high-power applications due to its low switching frequency and high quality output voltage. This paper proposes a new expression for the SHE problem in five-level converters. Based on this new expression, a simple analytical method is introduced to determine the feasible modulation index intervals and to calculate the exact value of the switching angles. For each selected harmonic, this method presents three-level or five-level waveforms according to the value of the modulation index. Furthermore, a flowchart is proposed for the real-time implementation of this analytical method, which can be performed by a simple processor and without the need of any lookup table. The performance of the proposed algorithm is evaluated with several simulation and experimental results for a single phase five-level diode-clamped inverter.

A New Symmetric Multilevel Inverter Topology Using Single and Double Source Sub-Multilevel Inverters

  • Ramani, Kannan;Sathik, Mohd. Ali Jagabar;Sivakumar, Selvam
    • Journal of Power Electronics
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    • v.15 no.1
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    • pp.96-105
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    • 2015
  • In recent years, the multilevel converters have been given more attention due to their modularity, reliability, failure management and multi stepped output waveform with less total harmonic distortion. This paper presents a novel symmetric multilevel inverter topology with reduced switching components to generate a high quality stepped sinusoidal voltage waveform. The series and parallel combinations of switches in the proposed topology reduce the total number of conducting switches in each level of output voltages. In addition, a comparison between the proposed topology with another topology from the literature is presented. To verify the proposed topology, the computer based simulation model is developed using MATLAB/Simulink and experimentally with a prototype model results are then compared.

Design of Multilevel Variable Output Voltage AC-DC Converter for Power Amplifier of Underwater Acoustic Sensor (수중 음향센서용 전력증폭기를 위한 멀티레벨 가변전압출력 AC-DC 전원회로 설계)

  • Lee, Chang-Yeol;Kim, In-Dong;Nho, Eui-Cheol;Moon, Won-Kyu;Kim, Won-Ho
    • The Transactions of the Korean Institute of Power Electronics
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    • v.18 no.1
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    • pp.72-83
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    • 2013
  • The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

A Novel Modulation Scheme and a DC-Link Voltage Balancing Control Strategy for T-Type H-Bridge Cascaded Multilevel Converters

  • Wang, Yue;Hu, Yaowei;Chen, Guozhu
    • Journal of Power Electronics
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    • v.16 no.6
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    • pp.2099-2108
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    • 2016
  • The cascaded multilevel converter is widely adopted to medium/high voltage and high power electronic applications due to the small harmonic components of the output voltage and the facilitation of modularity. In this paper, the operation principle of a T-type H-bridge topology is investigated in detail, and a carrier phase shifted pulse width modulation (CPS-PWM) based control method is proposed for this topology. Taking a virtual five-level waveform achieved by a unipolar double frequency CPS-PWM as the output object, PWM signals of the T-type H-bridge can be obtained by reverse derivation according to its switching modes. In addition, a control method for the T-type H-bridge based cascaded multilevel converter is introduced. Then a single-phase T-type H-bridge cascaded multilevel static var generator (SVG) prototype is built, and a repetitive controller based compound current control strategy is designed with the DC-link voltage balancing control scheme analyzed. Finally, simulation and experimental results validate the correctness and feasibility of the proposed modulation method and control strategy for T-type H-bridge based cascaded multilevel converters.

Modeling, Analysis, and Enhanced Control of Modular Multilevel Converters with Asymmetric Arm Impedance for HVDC Applications

  • Dong, Peng;Lyu, Jing;Cai, Xu
    • Journal of Power Electronics
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    • v.18 no.6
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    • pp.1683-1696
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    • 2018
  • Under the conventional control strategy, the asymmetry of arm impedances may result in the poor operating performance of modular multilevel converters (MMCs). For example, fundamental frequency oscillation and double frequency components may occur in the dc and ac sides, respectively; and submodule (SM) capacitor voltages among the arms may not be balanced. This study presents an enhanced control strategy to deal with these problems. A mathematical model of an MMC with asymmetric arm impedance is first established. The causes for the above phenomena are analyzed on the basis of the model. Subsequently, an enhanced current control with five integrated proportional integral resonant regulators is designed to protect the ac and dc terminal behavior of converters from asymmetric arm impedances. Furthermore, an enhanced capacitor voltage control is designed to balance the capacitor voltage among the arms with high efficiency and to decouple the ac side control, dc side control, and capacitor voltage balance control among the arms. The accuracy of the theoretical analysis and the effectiveness of the proposed enhanced control strategy are verified through simulation and experimental results.

Investigation of Capacitor Voltage Regulation in Modular Multilevel Converters with Staircase Modulation

  • Shen, Ke;Wang, Jianze;Zhao, Dan;Ban, Mingfei;Ji, Yanchao;Cai, Xingguo
    • Journal of Power Electronics
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    • v.14 no.2
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    • pp.282-291
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    • 2014
  • This paper presents a detailed theoretical analysis and performance assessment of the capacitor voltage balancing strategies for staircase modulated modular multilevel converters (MMC) in terms of the algorithm structures, voltage balancing effect, and switching frequency. A constant-frequency redundancy selection (CFRS) method with minimal switching loss is proposed and the function realization of specific modules of the algorithm is given. This method is simple and efficient in both switching frequency and regulation capacity. Laboratory results show very good agreement with the theoretical analysis and numerical simulations.