Bi-directional power flow controlled multi-level mutual balance solid state transformer and realization method thereof

Abstract

The invention relates to a bi-directional power flow controlled multi-level mutual balance solid state transformer and a realization method thereof. The solid state transformer is a three-phase solid state transformer which is designed by using a mutual balance structure, and uses an AC-DC-AC three step type transform structure. A high voltage level, an isolation level and a low voltage level are comprised. The high voltage level and the isolation level are transformers with the same three-phase structure and are composed of sub units. The low voltage level is a single whole module which realizes an automatic mutual balance structure. Three-phase sub units of the high voltage level are connected in a star mode. The low voltage level is an alternating current output end with a three-phase four-wire wiring mode. The solid state transformer can realize power bi-directional flow. The whole three-phase system uses an independent structure, which is convenient for three-phase independent control and modular production. Through the direct current bus parallel module of the low voltage level, a three-phase electric power automatic mutual balance function is realized, so that the practical problem of the solid state transformer is solved.

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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