Energy Equivalent Modeling Method for Modular Multilevel Converter

Abstract

The invention relates to an energy equivalent modeling method of a modular multilevel converter. Establish a modular multilevel converter bridge arm and sub-module electrical independent model; in the sub-module equivalent process, classify the conduction voltage drop of the sub-module switching device and the sub-module capacitor voltage, simplify the calculation process, and use energy conservation The principle is to update and calculate the capacitor voltage of the sub-module to ensure the internal characteristics of the converter; the bridge arm of the modular multi-level converter is equivalent to the whole by the controlled voltage source to ensure the accurate output characteristics of the converter. The method of the present invention can efficiently and accurately realize MMC modeling in electromagnetic transient simulation, and its electromagnetic transient simulation calculation complexity is greatly reduced; it has a good reference effect for MMC researchers, so that the subsequent system simulation analysis work can be carried out smoothly .

Description

technical field [0001] The invention relates to an energy equivalent modeling method of a modular multilevel converter. Background technique [0002] Modular multilevel converter (MMC) has received extensive attention since it was proposed, and has shown great advantages in high voltage direct current transmission (HVDC) engineering applications, becoming the future development direction of this field. The application of MMC solves the shortcomings of traditional DC transmission, such as easy failure of commutation, low output voltage, and high harmonic content of output voltage and current, and can realize reliable and effective power flow control. Comply with the application requirements of flexible power transmission in the current environment of interconnection of large power grids and smart grids. [0003] Since the MMC technology is still in the stage of application development, the operating data of the system under different working conditions are incomplete, and it...

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Problems solved by technology

[0013] The model modeling method based on Thevenin's equivalent principle is relatively complicated, and the sub-module capacitance update adopts traditional integration methods such as trapezoidal integration method and backward Euler method, and the calculation process ignores the capacitance voltage variation of each sub-module in the same simulation cycle The independence of the MMC affects the simulation accuracy of the internal characteristics of the MMC

The general equivalent model of the controlled source contains a large number of nonlinear elements in large-scale MMC simulation, which makes the simulation time greatly increase with the increase of the number of levels, which is not suitable for large-scale simulation

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