Modular multilevel DC transformer and its modulation method

Abstract

The invention provides a modular multi-level DC transformer and a modulation method thereof, wherein the DC transformer includes a transformer sub-module; the transformer sub-module includes a primary side part, a secondary side part and an energy storage capacitor part; the primary The three parts of the side part, the secondary side part and the energy storage capacitor part are cascaded; the energy storage capacitor part includes a capacitor; the primary side part and the secondary side part are connected to the energy storage capacitor through a switch tube in reverse series partially connected. The topology of the invention has no internal AC link transformer, realizes the direct power conversion between the DC primary side and the DC secondary side, improves the transmission efficiency, and reduces the size of the device; the modular structure of the topology increases the system redundancy and can improve the reliability of the device ; The application of the new sub-module can realize the large-scale online adjustment function of the transformation ratio of the DC transformer system.

Description

technical field [0001] The present invention relates to the field of direct current transmission and the field of design and control of power electronic converters, in particular to a modular multilevel direct current transformer and its modulation method, especially to the topology design and operation of a modular multilevel direct current transformer control. Background technique [0002] DC power grid is an important direction for future power grid development. Medium-voltage and large-capacity DC transformers are one of the key core components of DC power grids. Scholars at home and abroad have increasingly in-depth research on DC transformers, and have proposed a variety of topological structures. Resonant DC transformers are developed from low-voltage switching power supplies and have the advantages of high power density and high change efficiency. However, the design of the inductance and capacitance parameters is complex, and the switching devices have limited wit...

AI Technical Summary

Problems solved by technology

like Figure 5 The shown is a DC transformer based on a new sub-module structure. Based on the idea of ​​shared capacitors and modular switching, it also significantly reduces the size and cost of the device, and has the ability to dynamically adjust the ratio. However, its sub-module structure is relatively complicated. Control strategy design is more complex

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