Large-scale wind power integration flexible direct-current power transmission fault current cooperative inhibition method

Abstract

The invention relates to a large-scale wind power integration flexible direct-current power transmission fault current cooperative inhibition method, and belongs to the technical field of flexible direct-current power transmission. When it is detected that the direct-current voltage is lower than a threshold value Udcth and the direct-current change rate is larger than a threshold value epsilon, the converter station is immediately switched to active current limiting control, that is, the total input number of all phases of sub-modules is reduced to kN (k is smaller than or equal to 1) in thenearest level approximation modulation process, and the k value is determined according to the wind power plant grid-connected bus voltage requirement. A dissipation resistor configuration method integrated with a current limiting function is designed, dissipation resistors are distributed and configured on upper and lower bridge arms of each phase, and meanwhile, the capacity of solving the problem of power surplus and reducing the current stress of a converter valve is achieved. Finally, a coordination and cooperation method of the two and the direct-current circuit breaker is designed, fault current is restrained cooperatively while safe operation of the wind power plant is guaranteed, and therefore the requirements for the on-off speed, capacity and manufacturing cost of the direct-current circuit breaker are reduced. The method has the advantages of being scientific, reasonable, high in applicability and good in effect.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a method for collaborative suppression of fault current in flexible direct current transmission with large-scale wind power access. Background technique [0002] Modular multilevel converter based high voltage direct current (MMC-HVDC) technology has good application prospects in the fields of large-scale renewable energy generation integration, multi-energy complementarity and friendly grid connection. . In order to meet the needs of large-scale development and long-distance transmission of renewable energy, the use of overhead lines to construct multi-terminal flexible DC power grids has become an inevitable trend in the development of future power grids. Compared with cable lines, overhead lines increase the probability of short-circuit faults. Therefore, fault clearance and protection issues are research hotspots in this field. Using DC circuit ...

AI Technical Summary

Problems solved by technology

However, due to the difficulty in manufacturing the current limiting device and increasing the construction cost, the economy is poor, and the engineering practicability needs to be certified.

Another solution is to use the controllability of power devices to suppress the fault current by reducing the source-side voltage, that is, to use the regulation ability of the half-bridge MMC to realize the fault current limit, but the existing method will cause its AC outlet voltage to be zero, and the bridge The arm will be subjected to three-phase short-circuit overcurrent, and it will have a great impact on the AC system, which will endanger the safe and stable operation of the wind farm, and it is difficult to apply to the flexible DC transmission system for large-scale wind power access.

In addition, the existing current limiting measures are single, and the fault current cooperative suppression method is still blank

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