A control method and system for modular multi-level flexible DC converter station

Abstract

The present invention provides a control method and system for a modular multi-level flexible DC converter station. The control method includes the steps: the three-phase AC information obtained by sampling is respectively passed through a virtual synchronous motor controller and a circulating current controller, Obtain the induced electromotive force and voltage regulation; obtain the three-phase voltage reference value according to the induced electromotive force and voltage regulation; modulate the three-phase voltage reference value through PWM, and output switching signals to realize the control of the modular multi-level converter station. The control method proposed by the invention can automatically adjust the output active power and reactive power according to the frequency and voltage variation of the AC system, thereby effectively reducing the frequency and voltage fluctuations of the AC system.

Description

technical field [0001] The invention relates to the technical field of flexible direct current transmission, in particular to a virtual synchronous motor control method and system for a modular multi-level flexible direct current converter station. Background technique [0002] In the face of the worldwide fossil energy crisis, global climate change and environmental degradation, countries around the world have fully realized that the development and utilization of energy must transition from traditional fossil energy to green, renewable and clean energy. As important renewable energy sources, wind power and photovoltaic power generation have become the main forms of energy supply. As the penetration rate of distributed energy increases, the installed capacity of traditional synchronous generators decreases, and the rotating reserve capacity and moment of inertia of the power system are relatively reduced. In addition, due to the joint action of distributed energy fluctuatio...

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Problems solved by technology

In traditional flexible HVDC transmission systems, space-oriented vector decoupling is easily affected by system control parameter changes and mismatches

In addition, the grid-connected converter under the traditional vector control strategy is difficult to provide appropriate damping in the low frequency band, which is likely to cause subsynchronous resonance of the AC system and large-scale off-grid of the grid-connected converter station, which seriously threatens the voltage and frequency of the power system. The stability of the system, especially during the transient fault of the power system, the grid-connected converter station cannot provide enough inertia, which can easily cause system frequency instability

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