Modular multilevel converter voltage-sharing control method

Abstract

The invention discloses a modular multilevel converter (MMC) voltage-sharing control method, belonging to the capacitance voltage control technical field. The method comprises: initializing capacitance voltage values of all sub modules in a voltage-sharing controller; collecting the bridge arm current of each phase of a MMC, utilizing the voltage and current relation of capacitors to perform differencing to obtain the capacitance voltage change values of all the sub modules in each control period, and correcting the capacitance voltage of all sub modules in the voltage-sharing controller; collecting a small amount of capacitance voltages to obtain the error between a capacitance voltage storage value in the voltage-sharing controller and a capacitance voltage collection value, and correcting the capacitance voltage of all sub modules in the voltage-sharing controller again. The method realizes MMC voltage-sharing control through collecting bridge arm current and a small amount of capacitance voltages, can avoid real time collection of a great amount of sub module capacitance voltages, and guarantee voltage-sharing control effects, and provides a feasible solution for reducing data traffic in practical voltage-sharing control, and improving engineering efficiency.

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, HVDC 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 superposition output i...

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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 a real-time simulator (RealTimeDigitalSimulation, RTDS), using optical fiber to transmit the capacitor voltage of 512 sub-modules takes time. 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 and then merge them together for sorting, which will also consume more control time

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