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Modular multilevel converter with thyristor DC-link switch for full-torque variable-speed drives

Zhou, Shaoze, Li, Binbin, Xu, Dianguo and Li, Gen ORCID: 2023. Modular multilevel converter with thyristor DC-link switch for full-torque variable-speed drives. CSEE Journal of Power and Energy Systems 9 (1) , pp. 293-305. 10.17775/CSEEJPES.2021.00500

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The modular multilevel converter (MMC) is a promising topology for medium-voltage drive applications due to its high-quality output waveforms, low device switching frequency and voltage rating. However, the large cell capacitor voltage ripple is a severe challenge faced by MMC at low motor speeds. Recently, a hybrid MMC (HMMC) topology is proven to be a competitive solution because of its lower cell capacitor voltage ripple and no common-mode voltage (CMV) problem compared with other methods. However, the dc-link switch with IGBT limits HMMC to be applied for high-voltage applications. This paper uses the thyristor instead of IGBT as the dc-link switch. To ensure the thyristor can be softly turned on and safely turned off, a new control scheme is proposed. When using this proposed scheme, HMMC can also tolerate the failure of thyristor's turning-off without shutting down the system, improving the reliability effectively. The cell capacitor voltage ripple analysis is presented considering the effects of the thyristor switching process. In addition, a decoupled energy balancing control is utilized to suppress the fluctuation of dc current. Experimental results obtained from a 380 V/7.5 kW downscaled prototype validate the effectiveness of starting up a motor from the standby mode to rated speed with full-torque.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Engineering
Publisher: IEEE
ISSN: 2096-0042
Date of First Compliant Deposit: 10 June 2021
Date of Acceptance: 10 June 2021
Last Modified: 07 Nov 2023 01:07

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