A five-level sub-module capacitor voltage balance control method for a modular multilevel converter

Abstract

The present invention provides a five-stage sub-module capacitor voltage balance control method of a modular multilevel converter, which superimposes an additional energy balance control component between bridge arms on the existing control method, and balances with the existing bridge arm internal voltage The combination of control methods is applicable to half-bridge sub-modules, full-bridge sub-modules and hybrid sub-module multilevel circuits. The five-level sub-module capacitor voltage balance control methods include the first-level single sub-module capacitor voltage closed-loop feedback control, the second-level half-bridge arm capacitor voltage closed-loop feedback control, the third-level full-bridge arm capacitor voltage closed-loop feedback control, and the fourth-level Closed-loop feedback control of capacitor voltage between two bridge arms and closed-loop feedback control of capacitor voltage between five-stage three-phase three-bridge arms. The invented control method is helpful to improve the stability of the system under different load conditions, improve the power quality of the capacitor voltage of the direct current transmission system, reduce the investment cost of the modularized multi-level power transmission system, and improve the stability and reliability.

Description

technical field [0001] The invention relates to a five-level sub-module capacitor voltage balance control method of a modular multilevel converter in the field of power systems. Background technique [0002] In recent years, with the increasingly serious problems of energy crisis and environmental pollution, countries around the world are vigorously developing and utilizing clean energy. However, in view of the large population expansion and limited power supply and transmission lines, there is an urgent need for more flexible, economical and environmentally friendly power transmission methods Realize more stable and efficient power transmission. Modular multilevel converter (Module Multilevel Converter, MMC) technology effectively provides power supply mode and quality, and solves the withstand voltage problem of switching devices. At the same time, because this converter adopts a highly modular structure and has strong scalability, it is widely used to implement flexible ...

AI Technical Summary

Problems solved by technology

[0004] To sum up, the existing sub-module capacitor voltage balance control technology is mainly through a large number of programming, detection and sorting software control or additional additional devices to achieve auxiliary control, which increases costs and uncertain factors. For reliable and stable capacitors Voltage balance control, these control methods or strategies are more difficult in practical application

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