Voltage-sharing and power-sharing control method of single-phase multi-module cascading solid-state transformer

Abstract

The invention discloses a voltage-sharing and power-sharing control method of a single-phase multi-module cascading solid-state transformer. A power main circuit part of the single-phase solid-state transformer is composed of an AC / DC rectifying input stage, a DC / DC middle stage and a DC / AC output stage. The rectifying stage and the middle stage serve as a system for controlling and designing, a common duty ratio control strategy based on single-phase d-q vector control is adopted in the input stage, the output direct voltage of the middle stage serves as feedback quantity of an outer voltage loop, the stability of the output direct voltage of the middle stage is achieved, and a unity power factor of an input end of a power grid is achieved; a control strategy based on voltage feed-forward and voltage feed-backward is introduced into all modules in the middle stage at the same time, the voltage feed-forward serves the benchmark of the voltage feed-backward, and errors of the voltage feed-forward and voltage feed-backward serve as the benchmark of a module current inner loop after being output by a voltage PI regulator. The front stage control strategy is interacted with the middle stage control strategy, and therefore the purposes that voltage and the power of modules of an SST are balanced, the power grid side unity power factor is achieved, the power grid current sine degree is high, the voltage stress of a switch tube is low, and the ripple of the output direct voltage of the middle stage is low.

Description

technical field [0001] The invention relates to the application of power electronics technology in power systems, in particular to a multi-module cascaded SST (solid-state transformer) voltage equalization and power control method. Background technique [0002] Since the traditional power transformer was invented, it has become an indispensable and important part of the power system because of its reliable operation and simple structure, and has a huge number of applications. But it has significant disadvantages: bulky, bulky; output voltage cannot be maintained constant, etc. Its main function is to realize isolation and voltage level transformation, the function is simple, and it has no ability to improve the power quality of the grid. [0003] The concept of solid-state transformer has long been proposed, and it mainly realizes voltage conversion and energy transfer by using power electronic devices and power electronic technology. Its outstanding feature is that it can...

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Problems solved by technology

[0006] The purpose of the present invention is to provide a single-phase multi-module cascaded solid-state transformer voltage equalization power control method for the shortage of unbalanced voltage and power existing in the existing cascaded modules

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