Harmonic resonance suppression method and system of flexible direct current power transmission system

Abstract

The invention discloses a harmonic resonance suppression method and system of a flexible direct current power transmission system, and relates to the technical field of power systems. The method comprises the following steps of: acquiring a three-phase current signal and sending the signal to an analog-to-digital converter to obtain a current digital signal; performing Hanning windowing Fourier transform processing on the current digital signal to obtain resonance information; according to the resonance information, constructing an ideal same-frequency positive-sequence three-phase voltage; performing phase locking processing on the same-frequency positive-sequence three-phase voltage to obtain a phase locking result; performing proportional integral control on a specific harmonic component of the current digital signal based on a phase locking result to obtain a preliminary voltage reference value; and superposing the initial voltage reference value with a voltage reference value generated by the current inner loop to obtain a final voltage reference value. According to the harmonic resonance suppression method, resonance mode information is determined through broadband resonance detection, harmonic current control is corrected according to the resonance mode information, and a set of complete closed-loop control strategy is formed; and the problem of suppression failure caused by the change of the system operation mode in the existing suppression method is avoided.

Description

technical field [0001] The invention relates to the technical field of power systems, in particular to a method and system for suppressing harmonic resonance of a flexible direct current transmission system. Background technique [0002] Modular multilevel converters are widely used in long-distance power transmission and grid asynchronous interconnection due to their advantages of modular structure, control flexibility and high power quality; The flexible DC transmission technology based on modular multilevel converters has been adopted in DC back-to-back networking projects. Stability problems in flexible DC systems have mostly occurred in the low-frequency and sub / supersynchronous frequency bands in the past, but in recent years there have been many actual high-frequency resonance events, with resonant frequencies reaching several thousand Hertz. High-frequency resonance events will cause accidents such as tripping of the flexible DC unit and system shutdown. The stabil...

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Problems solved by technology

[0004] In the existing technology, the system impedance will change continuously with the system operation mode (such as AC network topology, power grid strength, etc.), resulting in a wide frequency range of flexible direct broadband resonance, and the frequency difference of different resonance events in the same system can even be It can reach hundreds of hertz, and the suppression method designed according to a specific resonance event is difficult to solve the broadband resonance problem of the actual flexible DC transmission system

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