High-frequency link interconnected three-port MMC-SST topology and control strategy

Abstract

The invention discloses a high-frequency link interconnected three-port MMCSST topology. The topology comprises a modular multilevel converter structure, a half-bridge and capacitor structure, a resonant push-pull converter and a three-phase bridge arm, wherein the resonant push-pull converter and the half-bridge and capacitor structure form an isolation sub-module; a high-frequency link of the resonant push-pull converter interconnects all the isolation sub-modules together to form a low-voltage direct-current bus, each phase of bridge arm in the three-phase bridge arm is divided into an upper bridge arm and a lower bridge arm, each phase of upper bridge arm comprises n isolation sub-modules and upper bridge arm inductors Lg1, Lg3 and Lg5, and each phase of lower bridge arm comprises n isolation sub-modules and lower bridge arm inductors Lg2, Lg4 and Lg6, according to the topology, SM capacitor voltage ripples and double-frequency circulating currents in bridge arms are eliminated, and voltage balance among all SM is realized.

Description

technical field [0001] The invention relates to the field of a solid-state transformer applied to a medium-low voltage hybrid AC-DC networking system, in particular to a three-port MMC-SST topology and control strategy for high-frequency link interconnection. Background technique [0002] With the increase of renewable energy penetration rate and the gradual increase of the proportion of DC load, DC system has been more and more widely used in power transmission and smart grid. Compared with the AC system, the DC system has more advantages in reducing the number of conversion stages, reducing transmission loss, avoiding harmonics and reactive power, and improving system response speed and stability. Hybrid AC and DC transformer technology has also received more and more attention. Solid-state transformers, also known as power electronic transformers, are new power electronic devices that combine power electronics technology with high-frequency power conversion technology. ...

AI Technical Summary

Problems solved by technology

However, these are all realized based on the closed-loop control of additional circuits, which require a large number of detection circuits and control computing resources.

And all the above studies on voltage ripple suppression are based on the precondition of SM capacitor voltage balance, so the system also needs to design a voltage balance control strategy

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