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AC/DC decoupling control method of modular multi-level current converter and application thereof

A modular multi-level, decoupling control technology, applied in the direction of electrical components, etc., can solve the potential safety hazards of overcurrent or sub-module capacitor overvoltage, closed-loop control of DC current and sub-module capacitor voltage, and non-real-time monitoring of residual voltage on the DC side Value and other issues, to achieve the effect of simple and reliable control, avoid damage, and reduce DC voltage

Active Publication Date: 2017-03-15
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology

The scheme of Kong Ming et al. has similarities with the scheme of CN104300569, the difference is that the residual voltage value of the DC side is not monitored in real time, but the residual voltage value of the DC side is artificially set to zero. The module capacitor voltage forms a closed-loop control, so there is a potential safety hazard of overcurrent or submodule capacitor overvoltage. Figure 12 It can be seen that during the DC fault, the DC current value rises from 1.6kA in the steady state to about 8kA at the moment of the fault, and the DC overcurrent multiple is as high as 5 times, which may burn the MMC

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  • AC/DC decoupling control method of modular multi-level current converter and application thereof
  • AC/DC decoupling control method of modular multi-level current converter and application thereof
  • AC/DC decoupling control method of modular multi-level current converter and application thereof

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[0051] In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not constitute a conflict with each other.

[0052] Figure 1 to Figure 4 It is a typical MMC topology applicable to the control method proposed by the present invention in the prior art. Such as Figure 1~4 shown, where figure 1 It is a full-bridge MMC, and each bridge arm is composed of multiple full-bridge sub-modules connected in series. figure 2 It is an MMC topology composed of cross-connected sub-modules, figure 2 Each bridg...

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Abstract

The invention discloses an AC / DC decoupling control method of a modular multi-level current converter. The method comprises the steps of adding DC current control in current inner-loop control so that current inner-loop control comprises AC current control and DC current control, thereby using output of the AC current control and output of the DC current control as main components of an output voltage reference value of each phase leg of the modular multi-level current converter; respectively controlling reference values of the AC current control and the DC current control, and simultaneously controlling outputs of the AC current control and the DC current control, thereby realizing control on main components, and furthermore preventing current converter locking because of a leg overcurrent in DC fault. The invention further discloses application of the method in a flexible DC power transmission system. The AC current and the DC current of each current converter station and capacitance and voltage of each submodule are controlled into a safe range, thereby realizing DC fault crossing of the flexible DC power transmission system.

Description

technical field [0001] The invention belongs to the technical field of electric power transmission and distribution, and more specifically relates to an AC / DC decoupling control method for a modular multilevel converter and its application in an overhead DC transmission system. Background technique [0002] Modular Multilevel Converter (MMC) technology has the advantages of modular structure and easy expansion. Since it was proposed, it has been widely used in the industry. So far, all the MMC HVDC transmission projects in the world have adopted the half-bridge type MMC technology based on the half-bridge sub-module (HBSM) or the same type of half-bridge sub-module (HBSM). Flat (Cascaded two level, CTL) technology. However, both the half-bridge MMC and CTL have the problem of being unable to cope with DC faults. After a DC fault occurs on the transmission line, the AC system will continue to provide fault current to the fault point through the freewheeling diode of the hal...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J5/00
CPCH02J5/00
Inventor 林卫星文劲宇程时杰
Owner HUAZHONG UNIV OF SCI & TECH
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