Single-phase direct-hanging AC-DC-AC converting system based on MMC (Modular Multilevel Converter)

Abstract

The invention discloses a single-phase direct-hanging AC-DC-AC converting system based on a MMC (Modular Multilevel Converter), which is formed by six MMC bridge arms in connection. P power modules with the same structures and an MMC bridge arm inductor L are connected in series to form each MMC bridge arm; the power module has a single-phase half-bridge structure and is formed by an IGBT half bridge and a DC energy storage capacitor; the six MMC bridge arms are in a three-phase connection and form two single-phase AC ports; and the two single-phase AC ports share the two MMC bridge arms in the six MMC bridge arms. The voltage phase difference of the two single-phase AC ports is 90 DEG, and the capacity of each sharing MMC bridge arm is the square root of 2 times of the capacity of the remaining MMC bridge arms. According to the single-phase direct-hanging AC-DC-AC converting system based on a MMC (Modular Multilevel Converter), voltage conversion and active power transfer between the two single-phase AC ports can be realized, the two single-phase AC ports can compensate reactive power respectively, and the system can be applied to frequency conversion occasions; a traction and matched transformer can be omitted, the occupied area and the investment can be reduced, the loss is reduced, and the efficiency is improved; and the system of the invention is advanced in technology, reliable and easy in implementation.

Description

technical field [0001] The invention relates to an MMC-based single-phase direct-connected AC-DC converter system, in particular to the technical fields of AC electrified railways and power electronics. Background technique [0002] With the rapid development of technology, the technology of power electronic devices to achieve voltage conversion and power transmission has been widely valued and applied. Compared with transformers, it has some obvious advantages: small size, less land occupation; output voltage amplitude remains constant (does not vary with load ), and can be adjusted smoothly; the current, voltage, and power are well controllable; the power factor is adjustable; it has the function of a circuit breaker, which can quickly limit and cut off faults, etc. There is also the performance that the transformer does not have - it can change the frequency and phase. [0003] There are two types of AC voltage conversion and power transfer realized by power electronics ...

AI Technical Summary

Problems solved by technology

The second is to adopt AC-DC conversion + medium-high frequency transformer + AC-DC conversion method, which is called power electronic transformer (PET, power electronic transformer) or solid-state transformer (SST, solid-state transformer), and the medium-high frequency transformer realizes voltage matching and isolation. The advantage is that the input side and the output side can be cascaded and are suitable for higher voltages. The volume of the medium and high frequency transformers is greatly reduced, but the structure is obviously complicated and the investment is increased.

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