Fault current-limiting control method and system for MMC type flexible direct-current power grid

A flexible DC, fault current limiting technology, applied in emergency protection circuit devices for limiting overcurrent/overvoltage, power transmission AC networks, information technology support systems, etc., can solve the problem of high cost of DC circuit breakers, reduce The effect of breaking capacity and cost reduction

Active Publication Date: 2020-02-11
HUAZHONG UNIV OF SCI & TECH
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Problems solved by technology

[0004] Aiming at the problem of high cost of the DC circuit breaker of the flexible DC grid in the prior art, the present invention provides a fault current limiting control method and system of the MMC type flexible DC grid. The purpose is to reduce the fault current of the flexible DC grid and reduce Technical Difficulties of DC Circuit Breakers

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  • Fault current-limiting control method and system for MMC type flexible direct-current power grid
  • Fault current-limiting control method and system for MMC type flexible direct-current power grid
  • Fault current-limiting control method and system for MMC type flexible direct-current power grid

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Embodiment Construction

[0042] 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.

[0043] Such as figure 1 As shown, the half-bridge modular multilevel converter is composed of three phase units connected in parallel, and each phase unit is composed of upper and lower bridge arm units and bridge arm inductors. Wherein, each bridge arm is formed by cascading half-bridge sub-modules.

[0044] Such as figure 2As shown, the sub-module hybrid modular multilevel converter compos...

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Abstract

The invention discloses a fault current-limiting control method and system for an MMC type flexible direct-current power grid, which belong to the field of power transmission and distribution of powersystems. By introducing a control variable of the modulation coefficient, the number of submodules actually inputted by a bridge arm unit of a converter is determined by the control signal outputtedby a pole controller and the modulation coefficient together, so that the bus voltage of the direct-current side outlet of the converter is positively correlated with the modulation coefficient. For aflexible direct-current power grid constructed by any type of modular multilevel converter, the number of submodules inputted by the bridge arm unit of the converter is obtained by multiplying the control signal outputted by the converter pole controller by the modulation coefficient. Under a fault condition, the modulation coefficient is reduced, the number of submodules inputted by the bridge arm unit is actively reduced by each converter, so that the DC voltage of the DC side outlet of the converter is reduced when a fault occurs, the fault current of the DC power grid is limited, the on-off capacity of the circuit breaker and the energy absorption of the parallel lightning arrester of the DC circuit breaker are reduced, and the cost is reduced.

Description

technical field [0001] The invention belongs to the field of power transmission and distribution of power systems, and more specifically relates to a fault current limiting control method and system of an MMC (Modular Multilevel Converter, modular multilevel converter) type flexible direct current grid. Background technique [0002] Flexible DC transmission technology has technical advantages such as decoupling control of active power and reactive power, and no commutation failure. It is an effective means to solve the problems of large-scale grid connection and long-distance transmission of wind power and photovoltaics. Due to the distribution characteristics of renewable energy in my country, the construction of flexible DC power grids based on overhead lines is an inevitable trend in future development. On the one hand, the application of overhead lines increases the failure probability of the DC grid. On the other hand, the DC system has low damping and the current rise ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J3/36H02H9/02
CPCH02H9/02H02J3/36Y02E60/60Y04S10/52
Inventor 文劲宇倪斌业向往周猛左文平姚伟
Owner HUAZHONG UNIV OF SCI & TECH
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