High-step-down-ratio multi-end DC transformer with fault ride-through capability

Abstract

The invention discloses a high-step-down-ratio multi-end DC transformer with a fault ride-through capability. The DC transformer is composed of two converters and is suitable for the interconnection of medium-and-low-voltage DC systems. The front-stage converter is connected with a medium-voltage DC line, is formed by cascaded full-bridge submodules, and realizes step-down and DC fault ride-through functions. The rear-stage converter is composed of a plurality of modules connected in parallel. Each module is composed of a bridge circuit and a high-frequency transformer, and is connected with alow-voltage DC line to realize isolation and voltage stabilization functions to meet different load requirements. When a bipolar short-circuit fault occurs at the medium-voltage side of the DC transformer, a fault characteristic is detected, the front-stage converter of the DC transformer is quickly locked, the reverse voltage is supplied to the DC line, the fault current is quickly reduced to zero, and the DC transformer restores to normal operation after the fault is cleared. In the whole fault occurrence, detection, clearing and recovery process, there is no need to disconnect the DC lineby a DC breaker, which is beneficial to the rapid recovery of the system to complete the bipolar short-circuit fault ride-through and achieve the stable operation of the DC system.

Description

technical field [0001] The invention belongs to the field of power electronics application technology, and in particular relates to a high step-down ratio multi-terminal DC transformer with fault ride-through capability. Background technique [0002] In the future, a large amount of clean energy and DC loads will be connected to the grid, and structural changes will occur on the source and load sides of the grid. With the maturity of power electronics technology, DC system can effectively integrate DC power supply and DC load, which is a very promising grid model. [0003] In the fields of communication, transportation, and renewable energy, low-voltage DC application technology has been well promoted. At the same time, with the joint efforts of scholars and enterprises, the high-voltage direct current transmission technology for high-power electric energy transmission has also made great progress. However, due to the lack of corresponding conversion and protection technol...

AI Technical Summary

Problems solved by technology

In addition to the requirements for voltage conversion and isolation, since DC transformers use power electronic devices, their reliability is lower than that of existing AC transformers, so DC transformers also need to have DC line fault ride-through capability

[0004] Few studies have been done on the high transformation ratio requirements of the interconnection of medium and low voltage DC systems and the safety of DC lines and DC transformers after a fault occurs. Therefore, it is urgent to propose a high step-down ratio DC transformer with fault ride-through capability.

Images