A kind of mmc-based solid-state transformer and its control method

Abstract

The invention provides a modular multilevel converter (MMC) based solid-state transformer and a control method thereof. The solid-state transformer comprises a high-voltage AC / DC converter, an isolated DC / DC converter and a low-voltage DC / AC converter, wherein the high-voltage AC / DC converter is connected with the isolated DC / DC converter through a high-voltage DC bus, and the isolated DC / DC converter is connected with the low-voltage DC / AC converter through a low-voltage DC bus parallel module. In the MMC based solid-state transformer, a medium- and low-voltage DC side adopts a DC bus staggered parallel topological structure, so that the unbalanced mutual influence of a high-voltage side system and a low-voltage side system of the solid-state transformer is solved from structure, and the power supply reliability is automatically improved; with the mutually-balanced solid-state transformer based on an MMC structure, the influence of a three-phase unbalance on a power grid and the influence of three-phase unbalance occurring in the power grid on an AC load can be prevented by controlling the constant voltage of a high-voltage common DC bus.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and in particular relates to an MMC-based solid-state transformer and a control method. Background technique [0002] Solid-state transformer is also called power electronic transformer or flexible transformer. It is a new type of transformer based on power electronic conversion technology and electromagnetic induction technology. It completely changes the system structure of traditional transformers. On the basis of basic functions such as electrical isolation and energy transfer, it can also realize many additional functions such as bidirectional power flow control and power quality control. It is the key equipment for the construction of the next generation of smart grid. Restricted by the development level of power electronic components, solid-state transformers that meet the requirements of the power grid for high voltage, high power, and high current that meet four-quadrant operat...

AI Technical Summary

Problems solved by technology

Currently, the commonly used solid-state transformer main circuit topology suitable for high-voltage and high-power occasions is mainly based on the H-bridge cascaded type (such as figure 1 ), solid-state transformers of neutral-point clamped multilevel converters, these topologies have many advantages, but there are also disadvantages such as difficult modular construction, complex control, and too many components required. The solid-state transformers of this type of topology The transformer does not have the function of automatically suppressing the mutual power quality interference between the grid and the load

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