High-frequency link technology-based isolation type modular multi-level converter

Abstract

The invention discloses a high-frequency link technology-based isolation type modular multi-level converter. The converter adopts a three-phase system structure and consists of single-stage high-frequency isolation type sub modules; the converter comprises three phase units connected between high-voltage direct current ports PH and NH in parallel; each phase unit consists of upper and lower bridgearms; the electric connecting point N1, N2 and N3 outgoing lines of the upper and lower bridge arms of the three phase units are connected with a filtering inductor in series to form high-voltage alternating current ports a, b and c; each bridge arm consists of n novel single-stage type high-frequency isolation type sub modules and a bridge arm electric reactor Lm; each single-stage type high-frequency isolation type sub module comprises a front-stage part, a high-frequency transformer part and a back-stage part; and the alternating current side of the front-stage part is connected with the primary side of the high-frequency transformer. By virtue of a combination of the high-frequency link technology and the modular multi-level technology, capacitor supporting and voltage-sharing controlon the high-voltage side of each module are not needed; and meanwhile, the problems of secondary side current conversion, voltage spike and the like of the conventional single-stage type converter are overcome.

Description

technical field [0001] The invention relates to the technical field of isolated modular multilevel power conversion, in particular to an isolated modular multilevel converter based on high frequency link technology. Background technique [0002] Isolated medium and high voltage AC-DC hybrid conversion technology will play an important role in the fields of new energy AC-DC hybrid smart grid, high-power motor drive and ship electric drive in the future. At present, the cascaded H-bridge type and the modular multilevel converter (MMC) type topology are widely used as two-stage power conversion systems. The problem is that the independent DC side of each module requires a large number of voltage stabilizing capacitors to buffer the single-phase system. The secondary power fluctuations make the device bulky, low power density, and high cost; at the same time, there is voltage imbalance between modules, requiring complex voltage balance control, which reduces system reliability. ...

AI Technical Summary

Problems solved by technology

At present, the cascaded H-bridge type and the modular multilevel converter (MMC) type topology are widely used as two-stage power conversion systems. The problem is that the independent DC side of each module requires a large number of voltage stabilizing capacitors to buffer the single-phase system. Secondary power fluctuations make the device bulky, low power density, and high cost; at the same time, there is voltage imbalance between modules, requiring complex voltage balance control, which reduces system reliability

Images