Grid fault ride-through control method for flexible direct-current transmission system

Abstract

The invention discloses a grid fault ride-through control method for a flexible direct-current transmission system. Grid fault non-communication ride-through of the system is achieved by switching converter station control modes, direct-current side voltage is detected in real time to judge whether a grid breaks down or not, control module switching is carried out, grid fault ride-through is achieved, and a controller supporting grid fault non-communication ride-through of the flexible direct-current transmission system is formed. By optimizing an original controller with the control method, direct-current voltage is effectively controlled in a grid fault of a constant direct-current voltage side converter station when no communication exists between converter stations under the condition that no hardware circuit is additionally arranged, the converter stations still keep operating during the grid fault, and meanwhile the system can be restored to an operating state before the fault as soon as possible after the fault is removed; grid fault non-communication ride-through of the flexible direct-current transmission system is achieved on the whole, the alternating-current fault ride-through capability of flexible direct-current transmission is improved, and a good operating environment is provided for the safety and stability of the system.

Description

technical field [0001] The invention belongs to the technical field of flexible power transmission and transformation, and relates to a method for grid fault ride-through control of a flexible DC power transmission system. Background technique [0002] The flexible DC transmission system based on the modular multilevel converter (MMC) will encounter AC grid drop faults in practical engineering applications. In order to reduce the impact on the AC grid and ensure the safety and reliability of the converter equipment itself, it is required When there is a grid voltage drop fault (such as a three-phase short-circuit fault, etc.), the converter should not perform fault blocking as much as possible but keep running, because the fault blocking of the converter and the re-closing after the fault recovery will affect the entire inverter. The DC parallel system brings great impact, and at the same time, the damage to the flexible DC transmission system is also huge. [0003] In orde...

AI Technical Summary

Problems solved by technology

In the case of no communication transmission between double-ended converter stations, if the grid fault occurs in the converter station on the constant DC voltage side, the converter station on the constant power side will continue to transmit to the converter station on the constant DC voltage side according to the state before the fault. power, the DC voltage of the system is out of control, and eventually the system of the flexible direct transmission system cannot operate normally

[0004] So far, the existing method of grid fault ride-through control of the converter station on the fixed DC voltage side of the flexible DC transmission system is mainly to add an additional circuit to the flexible DC transmission system. When the grid voltage fails, the remaining power is consumed to ensure the stability of the DC bus voltage. Although this method can Solve the DC out-of-control problem of the double-ended flexible direct current transmission system without inter-station communication, but the system adds additional circuits, which greatly increases the complexity of the system and reduces the reliability of the system. Therefore, the grid failure of the flexible direct current transmission system without additional circuits is designed The no-communication ride-through control method ensures that the constant DC voltage control converter station can stabilize the DC bus voltage after a grid fault occurs in the case of no communication between stations. The research work is extremely important

Images