Bidirectional high voltage dc/dc control method for multi-coil single-phase intermediate frequency square wave transformer

Abstract

The invention discloses a bidirectional high-voltage DC / DC control method of a multi-coil single-phase intermediate-frequency square wave transformer. Specifically, the intermediate-frequency transformer is that high-voltage and / or low-voltage windings adopt multi-coil structures in the same magnetic core coupling magnetic field, and each coil is independently led to a controller. The controller is of a modular multilevel half-bridge serial structure, each half bridge consists of two parallel branch circuits, one branch circuit consists of two power switch tube series circuits including antiparallel freewheel diodes, the other branch circuit consists of two series capacitors, and a middle point of the branch circuits is respectively connected with a coil of the transformer windings. The bidirectional high-voltage DC / DC control method can effectively improve the time change rates of voltage and current in the bidirectional intermediate-frequency transformer winding power flow control process, automatically achieves capacitor voltage balance, is flexible in control, can effectively solve the problem of uncontrollable voltage borne by power devices due to the fact that power control devices trigger breakover asynchronization and effectively inhibits charging current of a direct current capacitor and current ripples of a direct current power supply.

Description

technical field [0001] The invention relates to a multi-coil single-phase intermediate-frequency square-wave transformer, in particular to a bidirectional high-voltage DC / DC control method for a multi-coil single-phase intermediate-frequency square-wave transformer. Background technique [0002] With the development of HVDC transmission and distributed power utilization technology, multi-terminal DC power grid is the key technology of future distributed transmission and distribution network. There are no two AC grid interconnections in different grades of DC grids. The phase, frequency and amplitude matching conditions of the voltage must be met. It is isolated by an intermediate frequency transformer and adopts a topology of DC / AC / IF transformer / AC / DC to realize the DC grid. Interconnection, good fault tolerance. [0003] Sine wave intermediate frequency transformers need to adopt multi-level phase-shift control technology. The topology of multi-level control circuits usua...

AI Technical Summary

Problems solved by technology

Since half-bridge DC / DC converters are used before and after each isolation transformer, the efficiency of the multi-transformer system is low, and the withstand voltage of the single half-bridge control unit for the three-phase input of the system is low, which is not suitable for high-voltage DC input. In addition, although the output passes through the H-bridge control unit High voltage can be formed in series, but the output control unit has a large number of power switch tubes, which is not suitable for high-voltage direct current transmission

Images