A method for charging and discharging capacitors in Modular Multilevel Converter

Das, Anandarup; Nademi, Hamed; Norum, Lars

doi:10.1109/iecon.2011.6119454

Cited by 63 publications

(40 citation statements)

References 9 publications

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“…Additional charging methods for the capacitors are proposed in [17,18] to eliminate the unbalanced capacitor voltages in the charging process. These additional charging methods are quite different from the pulse width modulation (PWM) methods [22][23][24].…”

Section: Modular Multilevel Converter (Mmc) [1-4] Which Is Firstly Imentioning

confidence: 99%

“…Recent researches on start-up schemes for MMCs and conventional VSCs are presented in [17][18][19][20][21]. Additional charging methods for the capacitors are proposed in [17,18] to eliminate the unbalanced capacitor voltages in the charging process.…”

Section: Modular Multilevel Converter (Mmc) [1-4] Which Is Firstly Imentioning

confidence: 99%

“…Therefore, MMCs are considered as a more cost-and space-efficient VSC, which have drawn much attention of researchers recently [13][14][15]. However, for MMCs, the voltage balancing problem for the large number of flying capacitors is a great challenge [16].Recent researches on start-up schemes for MMCs and conventional VSCs are presented in [17][18][19][20][21]. Additional charging methods for the capacitors are proposed in [17,18] to eliminate the unbalanced capacitor voltages in the charging process.…”

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confidence: 99%

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A start strategy for synchronized connection of MMCs to an AC system

Liu

et al. 2015

International Journal of Electrical Power & Energy Systems

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Section: Modular Multilevel Converter (Mmc) [1-4] Which Is Firstly Imentioning

confidence: 99%

Section: Modular Multilevel Converter (Mmc) [1-4] Which Is Firstly Imentioning

confidence: 99%

mentioning

confidence: 99%

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A start strategy for synchronized connection of MMCs to an AC system

Liu

et al. 2015

International Journal of Electrical Power & Energy Systems

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“…In this condition, after the fault is cleared, the SM capacitors must be charged back to around the rated value as suggested in [16,17], and the MMC can then be restarted.…”

Section: Standby Operation Of the Dc/dc Converter During A Local Faultmentioning

confidence: 99%

AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

Rui

Fletcher

2016

Energies

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Abstract:The AC voltage control of a DC/DC converter based on the modular multilevel converter (MMC) is considered under normal operation and during a local DC fault. By actively setting the AC voltage according to the two DC voltages of the DC/DC converter, the modulation index can be near unity, and the DC voltage is effectively utilized to output higher AC voltage. This significantly decreases submodule (SM) capacitance and conduction losses of the DC/DC converter, yielding reduced capital cost, volume, and higher efficiency. Additionally, the AC voltage is limited in the controllable range of both the MMCs in the DC/DC converter; thus, over-modulation and uncontrolled currents are actively avoided. The AC voltage control of the DC/DC converter during local DC faults, i.e., standby operation, is also proposed, where only the MMC connected on the faulty cable is blocked, while the other MMC remains operational with zero AC voltage output. Thus, the capacitor voltages can be regulated at the rated value and the decrease of the SM capacitor voltages after the blocking of the DC/DC converter is avoided. Moreover, the fault can still be isolated as quickly as the conventional approach, where both MMCs are blocked and the DC/DC converter is not exposed to the risk of overcurrent. The proposed AC voltage control strategy is assessed in a three-terminal high-voltage direct current (HVDC) system incorporating a DC/DC converter, and the simulation results confirm its feasibility.

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“…Once the charging is completed, the resistances are bypassed through parallel-connected switches under normal operation. However, additional cost is a big issue due to large rating switches and resistances [17]. A pre-charging method using PWM switching techniques without additional circuits was proposed.…”

Section: Introductionmentioning

confidence: 99%

Improved Pre-charging Method for MMC-Based HVDC Systems Operated in Nearest Level Control

Kim¹,

Kim²,

Kim³

et al. 2017

Journal of Power Electronics

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Recently the researches on modular multi-level converter (MMC) are being highlighted because high quality and efficient power transmission have become key issues in high voltage direct current (HVDC) systems. This paper proposes an improved pre-charging method for the sub-module (SM) capacitor of MMC-based HVDC systems, which operates in the nearest level control (NLC) modulation and does not need additional circuits or pulse width modulation (PWM) techniques. The feasibility of the proposed method was verified through computer simulations for a scaled 3-phase 10kVA MMC with 12 SMs per each arm. Hardware experiments with a scaled prototype have also been performed in the lab to confirm the simulation results.

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A method for charging and discharging capacitors in Modular Multilevel Converter

Cited by 63 publications

References 9 publications

A start strategy for synchronized connection of MMCs to an AC system

A start strategy for synchronized connection of MMCs to an AC system

AC Voltage Control of DC/DC Converters Based on Modular Multilevel Converters in Multi-Terminal High-Voltage Direct Current Transmission Systems

Improved Pre-charging Method for MMC-Based HVDC Systems Operated in Nearest Level Control

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