MMC capacitor voltage equalization control method based on phase-shift space vector modulation

Abstract

The invention discloses a MMC capacitor voltage equalization control method based on phase-shift space vector modulation, which realizes capacitor voltage equalization of each sub-module based on phase-shift space vector modulation. The space vector of the first three-phase sub-module is calculated by using two-level space vector modulation algorithm in alpha' - beta' coordinates; In order to realize the control of the remaining (n-1) three-phase sub-modules, the first three-phase sub-module space vector modulation signal is phase shifted to obtain the modulation signals of the other (n-1) three-phase sub-modules; And forming a pulse signal based on the modulated signal and distributing the pulse signal to each half bridge sub-module to control the on-off of each half bridge sub-module insix bridge arms; In order to realize capacitor voltage equalization, the space vectors of n groups of three-phase sub-modules are distributed cyclically according to the reference voltage period in the next (n * 1) reference voltage periods. This method is easy to implement and has good scalability. It can significantly simplify the MMC sub-module capacitor voltage equalization control.

Description

technical field [0001] The present invention relates to the field of sub-module capacitor voltage equalization control method of modular multilevel converter (MMC) in the field of power electronics and automatic control, and relates to a MMC sub-module capacitor voltage based on phase-shifting space vector modulation The equalization control method specifically refers to a control method that adopts a cyclic phase-shifting space vector modulation strategy under the α'-β' coordinates to realize equalization of the capacitor voltage of the MMC sub-module. Background technique [0002] As a very popular circuit topology for medium-voltage and high-power converters, MMC has the following main advantages: highly modular structure, easy to expand system capacity and industrial production; no need for multiple isolated DC power supplies and output transformers, simplifying The circuit structure is improved to reduce the system loss; the low withstand voltage switching device is use...

AI Technical Summary

Problems solved by technology

However, when the SVPWM method is used in multilevel converters, with the increase of the number of levels, the number of basic vectors increases greatly, and the redundant switch state vectors also increase greatly. The selection of switch state vectors and the calculation of their action time are extremely complicated. It is difficult to implement the SVPWM method, especially when it is used for MMC modulation, it is difficult to achieve sub-module capacitor voltage balance control, so the SVPWM method is not suitable for MMC

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