Voltage-equalizing and power-equalizing control method for three-phase multi-module cascade solid-state transformer

Abstract

The invention discloses a voltage-equalizing and power-equalizing control method for a three-phase multi-module cascade solid-state transformer. A three-phase SST system power main circuit part applied in the method comprises an input stage, an intermediate stage and an output stage, wherein a control policy based on three-phase d-q-0 vector control is adopted in the input stage, a common duty ratio control policy is adopted in modules in the same phase so as to achieve the unit power factor of an input end of an electric network; a control policy based on voltage feedforward and voltage feedback is introduced for each module in the intermediate stage, the voltage feedforward is used as a reference of the voltage feedback, and an error between the voltage feedforward and the voltage feedback is used as a reference of an inner current loop of each module after being output by a voltage PI adjuster. The two control policies of the front stage and the intermediate stage interact so as to achieve the functions of voltage and power equalization of each SST module, electrical network side unit power factor, high electrical network current sine degree, low switching tube voltage stress and the like.

Description

technical field [0001] The invention relates to the application of power electronics technology in power systems, in particular to a three-phase 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, heavy; the output voltage cannot be kept constant; its main function is to achieve isolation and voltage level conversion, 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 three-phase multi-module cascaded solid-state transformer voltage equalization and power control method for the shortage of unbalanced voltage and power existing in the existing cascaded modules

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