VSC alternating current fault ride-through method and device of extra-high voltage hybrid multi-terminal direct current system

Abstract

The invention discloses VSC alternating current fault ride-through method and device of an extra-high voltage hybrid multi-terminal direct current system. The method comprises the following steps: determining whether a receiving end VSC has an alternating current fault or not according to an alternating current voltage of the receiving end VSC, and generating a fault signal and enabling an alternating current low-voltage current limiting link, a direct current modulation link and a positive and negative sequence current control link of the receiving end VSC with the fault when the receiving end VSC has the alternating current fault; sending the fault signal to a rectifier station and a non-fault inverter station, controlling the rectifier station to enter a DC voltage control mode, and controlling the non-fault inverter station to perform short-time power increasing operation; after the alternating current fault is removed, the faulted receiving end VSC is recovered to the normal working state, and a fault removing signal is generated; sending the fault clearing signal to a rectifier station and a non-fault inverter station, and recovering the rectifier station and the non-fault inverter station to a normal working state so as to recover the direct-current power of the extra-high voltage hybrid multi-terminal direct-current system; the method can improve the ride-through and recovery characteristics when an AC fault occurs at the inversion side, and improves the operation safety of the system.

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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