A Modular Multilevel Converter Voltage Equalization Control Method

Abstract

The invention discloses a voltage equalization control method for a modularized multilevel converter, which belongs to the technical field of capacitor voltage control. Initialize the capacitor voltage values ​​of all sub-modules inside the voltage equalizing controller; collect the bridge arm current of each phase of the modular multi-level converter, and use the voltage-current relationship of the capacitor for differential differentiation to obtain each control cycle of all sub-modules Correct the capacitor voltage of all sub-modules inside the voltage equalizing controller; by collecting a small amount of capacitor voltage, obtain the error between the stored value of the capacitor voltage inside the voltage equalizing controller and the collected value of the capacitor voltage, and correct the voltage equalizing control again Capacitor voltage of all sub-modules inside the device. The voltage equalization control of the modular multilevel converter is realized by collecting the bridge arm current and a small amount of capacitor voltage, which can avoid the real-time acquisition of the capacitor voltage of a large number of sub-modules and ensure the effect of voltage equalization control. In order to reduce the data communication in the actual voltage equalization control Quantity, improve engineering efficiency to provide a practical solution.

Description

technical field [0001] The invention belongs to the technical field of capacitor voltage control, and in particular relates to a voltage equalization control method for a modularized multilevel converter. Background technique [0002] With the development of voltage source converter (voltage source converter, VSC) and pulse width modulation technology, high-voltage direct current transmission technology has received more and more attention, and can be widely used in low-power transmission, renewable energy grid connection and Passive network powered. However, VSC usually adopts a 2-level or 3-level topology, which has disadvantages such as difficult dynamic voltage equalization and high switching frequency. Modular multilevel converter (MMC), as a new type of voltage source converter, has received more and more attention in research at home and abroad. Each bridge arm of the MMC is composed of multiple modular sub-modules and bridge arm inductors in series, and multi-level...

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Problems solved by technology

When the value of N becomes larger, the number of capacitor voltages to be collected will increase correspondingly, and the requirements for the control cycle will also be higher: In the real-time simulator (Real Time Digital Simulation, RTDS), the capacitor voltage of 512 sub-modules is transmitted by optical fiber, It takes 4 small steps with a total period of about 10us; in actual engineering, the voltage equalization control needs to collect the capacitor voltages of the sub-modules arranged in series in a scattered manner, and then merge them together for sorting, which will also consume more control time

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