A control method and a device for connecting wind power to a flexible HVDC transmission system

Abstract

The invention provides a control method and a device for connecting wind power to a flexible HVDC transmission system. Firstly, the actual frequency of an AC grid at a receiving end, the actual frequency of an AC bus bar at a wind farm side, the actual voltage at a DC side of a receiving end converter station are obtained, and the reference voltage at the DC side of the receiving end converter station is determined. Then, the voltage of DC line, the frequency of AC bus and the active power of wind farm are controlled separately, which has high reliability, short frequency modulation response time and good frequency modulation effect. Virtual synchronous machine droop control is adopted in the sending-end converter station, which improves the response speed of frequency regulation and shortens the time of frequency modulation. The frequency of the alternating current bus on the wind farm side is controlled by fixed frequency control or frequency conversion control, The active power of wind farm is controlled by virtual inertia, which makes the increased or decreased power released or supplemented in time when the flexible HVDC system provides frequency modulation for the receiving AC network, and reduces the risk of HVDC line voltage exceeding the limit, and greatly improves the reliability of HVDC system.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a control method and device for connecting wind power to a flexible direct current transmission system. Background technique [0002] As the installed capacity of wind farms increases, the proportion of wind power grid-connected to the entire grid capacity is also increasing, and the impact on the grid is also increasing. Long-distance large-scale wind farms can be integrated into the AC power grid at the receiving end through the flexible DC transmission system. In the power system, the rotors of synchronous motors and DC motors have rotational inertia and damping components, which contain a large amount of kinetic energy. When the power grid is disturbed or faulty, the rotor kinetic energy can be fully utilized to maintain the stability of the power grid. However, the flexible DC transmission system effectively decouples the direct connection betwe...

AI Technical Summary

Problems solved by technology

[0006] In order to overcome the shortcomings of low reliability, long frequency modulation response time and poor frequency modulation effect in the above-mentioned prior art, the present invention provides a control method and device for connecting wind power to a flexible direct current transmission system. The actual frequency of the AC bus on the wind farm side, the actual voltage of the DC side of the receiving end converter station, and determine the DC side reference voltage of the receiving end converter station according to the actual frequency of the receiving end AC grid; then based on the receiving end AC grid The actual frequency and the actual voltage of the DC side of the receiving-end converter station control the voltage of the DC line. Based on the actual DC-side voltage of the receiving-end converter station and the reference voltage of the DC side of the receiving-end The frequency is controlled, and the active power of the wind farm is controlled based on the actual frequency of the AC bus on the wind farm side, with high reliability and short frequency modulation response time. Considering the mutual cooperation between the flexible direct current transmission system and the wind farm control mode, the frequency modulation effect is good

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