Stepped Two-Level Operation of Nonisolated Modular DC/DC Converter Applied in High-Voltage DC Grid

The most critical problem of the modular DC-DC converter (MDCC) is the voltage balancing of the submodule (SM) capacitors, the MDCC with stepped 2-level modulation has been developed and presents a good solution, however, this type of modulation has many restrictions when there is a wide range of capacitance tolerance of the SM capacitors that results inaccurate capacitor voltages balancing. To solve this problem, this paper discusses a proposed method of capacitor voltage balancing. Compared with stepped 2-level modulation, the voltage balancing method using modified duty cycle modulation offers the merits: i) reduction in output voltage and SM capacitor voltages overshoot during dynamic operation and improvement in the time response of the system and; ii) accurate voltage balancing over wide range of capacitance tolerance of each SM capacitor; and iii) the sorting algorithm replaced with modified duty cycle modulation method for the SM capacitor voltages balancing which reduces the computation burden. The proposed method ensures a stable voltage balancing, improves the time response of the system, and decreases the voltage and current overshoot during the dynamic response compared with prior art of MDCCs, where the stepped 2-level modulation is adopted. An analytical simulation of the MDCC is presented using MATLAB/Simulink to explain the operation.

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“…According to You and Cai [29], the voltage-second balance of filter inductor Lf can be achieved, it easy to get.…”

Section: Steady State Operation and Analysismentioning

confidence: 99%

“…Combining ( 4) and ( 5) I1max and I1min can be expressed as: Returning to Figure 3, according to the waveforms of i1 and vCl1, chain link 1 absorb energy WCl1 in one period, and can be calculated as shown [29]:…”

Section: Steady State Operation and Analysismentioning

confidence: 99%

Capacitor voltages balancing method for buck modular DC/DC converter

Salih

Hassan

2022

IJPEDS

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“…When strict electrical isolation is not necessary and compact design is preferred, nonisolated MMDC becomes a better choice due to its small volume, high efficiency, and low cost. In order to avoid multilevel transformation, You and Cai 14 adopt the upper and lower arms of MMC to form a direct coupled MMDC topology. However, because of the different charging and discharging effects of dc current in upper and lower arms SMs, this kind of converter needs a power transmission circuit between the two arms to ensure power balance.…”

Section: Introductionmentioning

confidence: 99%

Multicell nonisolated resonant modular multilevel dc‐dc converter with self‐voltage balancing and step‐up conversion

Zhu

Jiang

Jin

et al. 2023

Circuit Theory & Apps

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SummaryWith the rapid development of renewable energy power generation technologies in high‐voltage direct‐current (HVDC) system, the high step‐up ratio dc‐dc conversion plays an important role to connect dc grids with different voltage levels. This paper presents a multicell nonisolated resonant modular multilevel dc–dc converter (MMDC) for medium‐ and high‐voltage applications. The converter exhibits expandability without using transformer. Moreover, by adding additional switched‐inductor (SL) cells, switched‐capacitor (SC) cells, and the upper arm submodules (SMs), the proposed converter can obtain high gain with low voltage stresses on switches and diodes. The operating states of SMs is regulated by the carrier phase‐shifted pulse width modulation (CPS‐PWM) to guarantee the number of inserted SMs is constant to support the high‐side load at any moment. The converter is operated in resonant mode with resonance between SM capacitors and arm inductor. The step‐up ratio could be regulated by adjusting the number of SL cells, SC cells, and upper arm SMs; thus, more flexible voltage regulation can be realized. In addition, the proposed converter has the voltage self‐balancing capability of capacitors in SMs and SC‐cells without additional balancing control strategy. The topology configuration, parameter design guideline, operating principle, and comparison with other MMDCs are presented. Finally, the theoretical analysis is verified by the simulation and bench‐scaled experimental prototype results.

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“…The Modular Multilevel Converter (MMC) fundamental structure have been used in a wide variety of topologies, given the provided modularity and the possibility to use relatively low voltage semiconductors in medium and high voltage dc and ac applications. Focusing on dc-dc converters, the Front-to-Front medium frequency isolated [1], the dc auto transformer [2] and the modular multilevel dc-dc family [3,4] are some topology examples recently approached in the literature.…”

Section: Introductionmentioning

confidence: 99%

Switching cell based on Hybrid Switched Capacitor and Modular Multilevel Converter

Novaes¹,

Soares²

2022

Preprint

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A switching cell based on Hybrid Switched Capacitor and Modular Multilevel Converters is presented. Automatic arms voltages clamping are achieved, while the current spikes and the efficiency dependence on duty cycle can be reduced by a proper design. A Buck type topology simulation and experimental results are presented and an example of cell application as a single-phase inverter is shown.

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Stepped Two-Level Operation of Nonisolated Modular DC/DC Converter Applied in High-Voltage DC Grid

Cited by 24 publications

References 32 publications

Capacitor voltages balancing method for buck modular DC/DC converter

Capacitor voltages balancing method for buck modular DC/DC converter

Multicell nonisolated resonant modular multilevel dc‐dc converter with self‐voltage balancing and step‐up conversion

Switching cell based on Hybrid Switched Capacitor and Modular Multilevel Converter

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