Method and system for suppressing DC overvoltage after blocking fault based on virtual modulation

Abstract

The invention discloses a DC overvoltage suppression method after a blocking fault based on additional virtual modulation, which includes: measuring the DC voltage signal when the new energy island is connected to the flexible direct grid; judging whether the additional virtual modulation control strategy is put into use based on the DC voltage signal; The time to reach the DC voltage limit is extended by using the additional virtual modulation control strategy, and the DC overvoltage after the blocking fault is suppressed. The invention aims at connecting the new energy island to the system through the multi-terminal true bipolar flexible direct grid. When the receiving end converter station or the AC system fails and the power output is blocked, an additional virtual modulation control strategy is used to reduce the power flowing into the DC grid and extend the The time to reach the DC voltage limit can suppress the rising speed of the DC voltage, and the economic cost is low. The additional virtual modulation control strategy is automatically turned on and off according to the DC voltage situation.

Description

technical field [0001] The invention belongs to the technical field of flexible direct current transmission protection and control, in particular to a method and system for suppressing direct current overvoltage after a blocking fault based on virtual modulation. Background technique [0002] The statements in this section merely provide background information related to the present disclosure and do not necessarily constitute prior art. [0003] In recent years, renewable energy, especially wind energy, has developed rapidly, and a large number of new wind energy has been connected to the grid. However, new energy AC grid integration faces bottlenecks such as poor transmission stability and low efficiency, and it is difficult to meet the needs of large-scale new energy power generation grid integration only by relying on the traditional AC grid transmission mode. The flexible DC transmission has the advantages of realizing passive grid connection of new energy power genera...

AI Technical Summary

Problems solved by technology

When the converter at the receiving end of the flexible direct grid has a blocking fault, the power of the new energy received at the sending end will not change, and the input power in the DC grid is higher than the output power, which will cause the DC voltage to rise. Due to the low power electronic devices With damping and low inertia characteristics, it only takes tens of milliseconds for the DC voltage to reach the overvoltage. Higher DC voltage will cause irreversible damage to power electronic devices and capacitors, endangering the safe and stable operation of the converter station

[0005] The inventor found in the research that, in view of the above problems, energy-dissipating resistors are generally used in existing projects to consume the surplus power in the DC grid, but the energy-dissipating resistors cost a lot of money and occupy a large area

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