Multi-level mutually balanced solid-state transformer with bidirectional power flow control and its realization method

Abstract

The invention relates to a multi-level mutually balanced solid-state transformer with bidirectional power flow control and a realization method thereof. The solid-state transformer is a three-phase solid-state transformer designed with a mutual balance structure. It adopts a three-stage AC-DC-AC conversion structure, including a high-voltage stage, an isolation stage, and a low-voltage stage. The high-voltage stage and the isolation stage are transformers with the same three-phase structure; They are all composed of sub-units; the low-voltage level is a separate integral module to realize an automatic mutual balance structure; the three-phase sub-units of the high-voltage level are connected in a star form, and the low-voltage level is an AC output terminal in a three-phase four-wire connection mode; the solid-state transformer can realize power two-way flow. The entire three-phase system adopts an independent structure to facilitate independent control and modular production of three phases. The parallel module of low-voltage DC bus makes it have the function of automatic mutual balance of three-phase electric energy, thus solving the practical problem of solid-state transformers.

Description

technical field [0001] The invention relates to a power electronic transformer, in particular to a multi-level mutual balance solid-state transformer with bidirectional power flow control and a realization method thereof. Background technique [0002] Solid-state transformer, also known as power electronic transformer or flexible transformer, is a new type of transformer based on power electronic conversion technology and electromagnetic induction technology. It has completely changed the system structure of traditional transformers and is the key equipment for the construction of the next generation of smart grid. However, due to the limitation of the development level of power electronic devices, the high-voltage, high-power, and high-current solid-state transformers that meet the needs of the power grid are still far from practicality. [0003] Solid-state transformer is a new type of power transformer that has been gradually developed with the development of high-power p...

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Problems solved by technology

However, at present, the maximum withstand voltage of this kind of device is lower than 6.5 kV, and the current low-voltage distribution transformer of the distribution network is also above 10 kV. If the device is used for voltage equalization in series, additional voltage equalization must be installed Even if the circuit and control method adopts a two-level structure in which power devices are directly connected in series, there are problems of dynamic and static voltage equalization, and the dv / dt is relatively large, which will cause difficult-to-handle electromagnetic interference problems, and there are power device failures or even shocks. wear and other hidden dangers

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