Hybrid multilevel converter

Abstract

The invention relates to a hybrid multilevel converter. The hybrid multilevel converter comprises a plurality of phase unit circuits, wherein each phase unit circuit comprises a first bridge arm, a second bridge arm, a third bridge arm, a first reactor, a second reactor, a first conduction switch and a second conduction switch, outgoing line positive electrode ends of DC sides of all phase unit circuits are connected, outgoing line negative electrode ends of the DC sides are connected, and an outgoing line end of an AC side of each phase unit circuit is connected with a power grid. Good AC / DC side harmonic characteristic can be acquired by filtering of reactors among the bridge arms, a DC filter is not needed to be additionally arranged, and the cost is effectively reduced; and moreover, rapid response can be achieved during the transient transition process, a surge current caused by discharge of the DC filter during the DC fault process is also prevented, and the circuit safety is guaranteed.

Description

technical field [0001] The invention relates to the technical field of power transmission, in particular to a hybrid multilevel converter. Background technique [0002] With the development of high-voltage flexible DC transmission technology, modular multilevel converters have become the preferred topology of flexible DC converter stations. However, there are a large number of sub-modules in the modular multi-level converter, and each sub-module includes capacitors and related measurement and control components, which greatly increases the cost and volume of the converter. In order to reduce the number of sub-modules inside the converter, existing research mainly uses cascaded insulated-gate bipolar transistors (IGBTs) in modular multilevel converters, that is, the design includes both cascaded IGBTs and IGBTs. Hybrid multilevel converter with cascaded sub-modules. [0003] In the hybrid multi-level converter, a design scheme is to use cascaded IGBTs inside the sub-modules...

AI Technical Summary

Problems solved by technology

However, since its cascaded IGBTs are located on the DC side, the harmonic characteristics of the DC side are poor, requiring a larger DC side filter

As the DC voltage increases, the size and cost of the DC side filter will increase significantly, thus limiting the application of these two converters in ultra-high voltage flexible DC transmission; in addition, in power steps, power flow reversals, etc. In the transient process, a larger DC side filter will prolong the time for the converter to transition to a steady state; during a DC fault, the discharge of the DC filter will cause a large surge current, which may damage the line and slow down the fault latching time

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