A method for identifying short-circuit faults inside hbsm-mmc based on AND-OR logic

Abstract

The invention discloses a method for recognizing an internal short-circuit fault of an HBSM-MMC (Half Bridge Sub-Module Modular Multilevel Converter) based on AND-OR logic. The method comprises the steps of (1) monitoring the state Sn of an nth HBSM; (2) monitoring capacitive voltage ucn of the nth HBSM, and calculating capacitive current icn of the nth HBSM; (3) calculating a ratio [lambda]n of the capacitive current of the nth HBSM and bridge arm current; (4) defining a threshold value K, recording [beta]n to be equal to 1 when the ratio [lambda]n is greater than or equal to the threshold value K, and recording [beta]n to be equal to 0 when the ratio [lambda]n is less than the threshold value K; and (5) when the state Sn is equal to 1, enabling the state Sn and the [beta]n to perform anAND operation, wherein AND is represented by *, and defining [rho]n1=Sn*[beta]n, and when the state Sn is equal to 0, enabling the state Sn and the [beta]n to perform an OR operation, wherein OR is represented by +, and defining [rho]n2=Sn+[beta]n, and [rho]n1=[rho]n2=0, wherein it is indicated that there is a short-circuit fault in the nth HBSM. The calculation method adopted by the invention issimple and convenient, the calculation result is simple in form and only has two forms such as 0 and 1, and the fault in the HBSM-MMC can be recognized and positioned quickly and accurately by using fewer parameters.

Description

technical field [0001] The invention belongs to the technical field of internal protection configuration of the HBSM-MMC body, in particular to a method for identifying short-circuit faults inside the HBSM-MMC based on "AND" and "OR" logic. Background technique [0002] Modular Multilevel Converter (MMC) is a new topology based on Voltage-sourced Converter based HVDC (VSC-HVDC). With the rapid development of power electronic devices such as insulated gate bipolar thyristor (Insulated Gate bipolar transistor, IGBT), MMC has been more and more widely used in the world. Compared with the traditional two-level or three-level VSC topology, MMC can reduce the switching frequency of the device, reduce the voltage change rate and current change rate of the device, thereby reducing the loss of the device and the difficulty of voltage equalization. [0003] The sub-module is the most critical component in the MMC topology. It not only assumes the role of the DC side capacitor of the ...

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Problems solved by technology

[0005] At present, there are few domestic and foreign literatures on short-circuit fault identification methods in HBSM-MMC. Wang Bo et al. (Wang Bo, Hu An, Tang Yong, etc. Analysis of IGBT voltage breakdown characteristics[J]. (8):145-150) analyzed the mechanism of IGBT overvoltage breakdown, but did not analyze the fault characteristics after breakdown; Liu Zhouzhou et al. [J]. Electric Transmission, 2015,45(3):77-80.) studied the mechanism of IGBT short-circuit protection, but did not have a corresponding solution; Chen Xikun et al. (Chen Xikun, Chen Xin, Kang Yong, etc. .A new type of IGBT short-circuit protection circuit design[J]. Automation and Instrumentation, 2003,9:45-47.) A method for directly detecting the short-circuit fault of the IGBT in the H-bridge is proposed, and the short-circuit fault of the IGBT is analyzed in detail Based on the detection principle, the corresponding IGBT short-circuit protection circuit is given, but there are differences between the short-circuit fault characteristics of the IGBT in the H-bridge and the IGBT in the HBSM, so this scheme cannot be directly used for the identification of the IGBT short-circuit in the HBSM; Sang Zixia et al. (Sang Zixia, Mao Chengxiong, Liu Jiming, etal.Analysis and simulation of fault characteristics of power switch failures in distribution electronic power transformers[J].Energies, 2013,6(8):4246-4268.) For cascaded H-bridge type IGBT short-circuit faults in power electronic transformers have been analyzed for fault characteristics, but no corresponding protection scheme has been given, and the fault characteristic analysis cannot be directly used for MMC

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