Modular solid-state transformer and its control method based on distributed high-frequency conversion

Abstract

The invention discloses a modular solid-state transformer based on distributed high-frequency conversion and its control method, which includes a plurality of cascaded modules, and each module includes two sub-converters SCi1 and SCi2, a high-frequency transformer and an auxiliary inductance L i , where i represents the i-th module. The sub-converter is composed of four power sub-modules, and the structure of the power sub-modules can be a half-bridge structure or a full-bridge structure. Each half bridge structure includes a capacitor, two IGBTs and diodes connected in reverse parallel with the IGBTs; each full bridge structure includes a capacitor, four IGBTs and diodes connected in reverse parallel to the IGBTs. The input end of the transformer is high voltage, and multiple modules are connected in series as the input end; the output end of the transformer is low voltage, and multiple modules are connected in parallel as the output end. The present invention can control the output voltage V of SCi1 hi1 and SCi2 output voltage V hi2 to control the current i hi1 The flow direction, that is, the control of the power flow direction, and the completion of voltage conversion and isolation.

Description

technical field [0001] The invention relates to a modularized solid-state transformer based on distributed high-frequency conversion, which is suitable for the application occasion of bidirectional conversion from high voltage to low voltage. Background technique [0002] Due to the vigorous development and utilization of new energy, the development of power electronics technology and the promotion of energy Internet, DC power grid technology has developed rapidly. Existing studies have shown that DC power grid technology is an effective way to solve problems such as cross-regional and large-scale power transmission and distribution, large-scale wide-area distributed new energy development and utilization, and can greatly ease the gap between large power grids and distributed energy. Contradictions, give full play to the benefits of distributed energy. The development of DC power grid has been widely concerned and recognized by experts and scholars from all over the world. ...

AI Technical Summary

Problems solved by technology

However, because this method increases the transition time of the voltage level change, it will bring a certain power loss compared with the direct use of square wave modulation.

At the same time, with the current high-frequency transformer production process, it is difficult to develop an insulation level of hundreds of kilovolts, but a high-frequency transformer with a capacity of megawatts can usually only obtain a higher insulation level by reducing the operating frequency. This limits the application of this topology in high voltage direct current (HVDC) transmission

In order to solve this problem, some scholars have proposed a structure in which multiple small-capacity high-frequency transformers are connected in series to replace a single high-frequency transformer. Uneven input voltage

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