VSC AC fault ride-through method and device for UHV hybrid multi-terminal DC system

Abstract

The invention discloses a VSC AC fault ride-through method and device of an ultra-high voltage hybrid multi-terminal DC system. According to the AC voltage of the receiving end VSC, it is judged whether an AC fault occurs in the receiving end VSC, and a fault signal is generated when an AC fault occurs in the receiving end VSC. And enable the AC low-voltage current limiting link, DC modulation link and positive and negative sequence current control link of the faulty receiving end VSC; send the fault signal to the rectifier station and the non-faulty inverter station, control the rectifier station to enter the DC voltage control mode, and Control the non-faulty inverter station to increase power for a short time; when the AC fault is cleared, restore the faulty VSC to the normal working state and generate a fault clearing signal; send the fault clearing signal to the rectifier station and the non-faulty inverter station , to restore the rectifier station and the non-faulty inverter station to the normal working state, so as to restore the DC power of the UHV hybrid multi-terminal DC system; the invention can improve the ride-through and recovery characteristics when the AC fault occurs on the inverter side, and improve the safety of the system operation .

Description

technical field [0001] The invention relates to the technical field of high-voltage direct current transmission, in particular to a VSC AC fault ride-through method and device for an ultra-high voltage hybrid multi-terminal direct current system. Background technique [0002] In the conventional DC transmission system, the inverter side is the LCC converter. When the AC voltage drops, the commutation failure is very likely to occur, which brings serious stability problems to the AC-DC system. When there are multiple DC drop in the same AC grid At this point, the stability problem is more prominent. The hybrid multi-terminal DC transmission system using LCC on the rectifier side and VSC on the inverter side does not have the problem of commutation failure, and is especially suitable for multi-drop DC applications, which is the trend of future power system development. [0003] However, there is no operation experience of this kind of hybrid DC system at present, which leads ...

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Problems solved by technology

[0003] However, there is no operation experience of this kind of hybrid DC system at present, which leads to many problems in actual operation. For example, when an AC fault occurs on the VSC side of the receiving end, the AC voltage drops and the DC side power cannot be sent. At this time, the DC side It will continue to charge the capacitor of the sub-module, which will cause the DC voltage to rise; the firing angle of the rectifier side will decrease rapidly, and when it reaches the minimum firing angle limit, it will lose the ability to adjust the DC voltage. If no appropriate control measures are taken at this time, The DC voltage will continue to soar; and the faulty VSC station is in an AC fault and has limited output current capability, so the ability to rely solely on VSC to discharge energy to avoid overvoltage is extremely limited, especially in the mixed operation mode of both ends

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