A seamless switching control method for AC/DC parallel systems based on vsc-hvdc

Abstract

The invention provides an alternating current-direct current parallel system seamless switching control method based on VSC-HVDC. According to the method, the phase shift angle delta, relative to a voltage vector Uw of a wind power plant PCC point, of a voltage vector Us of a power grid connected with an alternating current circuit is adjusted by controlling a synchronous rotation angle theta of a VSC-HVDC wind power plant side convertor station so that active power transmitted by an alternating current power transmission circuit can be controlled, and the rest of the active power is completely absorbed by a VSC-HVDC power transmission system. As the phase position of the voltage of the wind power plant PCC point is controlled to be ahead of the phase position of the voltage of the alternating current power grid all the time, the current of the alternating current power transmission circuit will not turn over; when the alternating current circuit stops operating, any external signal does not need to be detected, the control mode of the VSC-HVDC wind power plant side convertor station does not need to be changed either, and when the alternating current-direct current parallel operation mode is converted into the operation mode that wind power has access to the VSC-HVDC independently, all wind power is absorbed automatically.

Description

technical field [0001] The invention relates to the field of high-voltage direct current transmission, in particular to a VSC-HVDC-based seamless switching control method for an alternating current and direct current parallel system. Background technique [0002] With the increasingly prominent environmental protection and energy demand, wind power has become the most commercially developed emerging industry, and may become the most important alternative energy in the future. With its own characteristics, offshore wind power will become the focus of future wind power development. However, with the continuous increase of wind farm capacity and power transmission distance, the impact of wind farm AC grid connection on grid stability and power quality is becoming more and more serious. Among them, the system voltage stability and voltage fluctuation problems caused by grid-connected wind farms are the most typical. , has become a restrictive factor for wind farms to connect to...

AI Technical Summary

Problems solved by technology

However, the disadvantages of this method are: 1) The amplitude, frequency or phase of the stator voltage of the wind turbine often does not change clearly enough at the moment when the grid-connected mode changes, resulting in the inability to switch the control mode of the converter station in time, resulting in the failure of the AC-DC parallel system switching; 2) The moment of switching the control mode of the converter station often produces a large impact

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