Control method and system for modular multilevel flexible direct current converter station

Abstract

The invention provides a control method and system for a modular multilevel flexible direct current converter station. The control method comprises the steps of, obtaining an induced electromotive force and a voltage regulating voltage through three-phase alternating current information obtained by sampling via a virtual synchronous motor controller and a circulating current controller; according to the induced electromotive force and the voltage regulating voltage, obtaining a three-phase voltage reference value; and via modulation of the three-phase voltage reference value by PWM, outputting a switch signal, and achieving control of the modular multilevel converter station. The control method is advantageous in that, according to frequency and voltage variation of an alternating current system, active power and reactive power can be automatically adjusted and output, thereby effectively reducing frequency and voltage fluctuation of the alternating current 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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