Improved switched capacitor-accessed two-way DC transformer and control method thereof

Abstract

The invention discloses an improved switched capacitor-accessed two-way DC transformer and a control method thereof, and belongs to the technical field of electric power. The transformer is formed by connecting n identical DC conversion units at one port in series and at the other port in parallel; and each DC conversion unit comprises eight semiconductor switches, two auxiliary semiconductor switches, two DC capacitors, a high-frequency inductor and a high-frequency transformer. The method comprises the steps as follows: under the normal condition, high-voltage sides of the n DC conversion units are connected in series and then are connected to a high-voltage DC side through a DC electric reactor; low-voltage sides of the n DC conversion units are connected in parallel and then are directly connected to a low-voltage DC side; when smaller than k DC conversion units have internal faults, the DC conversion units with the faults are directly bypassed; and when an external fault appears at the high-voltage or low-voltage DC side, the semiconductor switches and the auxiliary semiconductor switches of all DC conversion units are turned off and the capacitor voltage can be kept constant. According to the improved switched capacitor-accessed two-way DC transformer, the operation economy and reliability of a device are improved.

Description

technical field [0001] The invention belongs to the technical field of electric power and relates to a solid-state transformer, in particular to an improved double-active full-bridge high-frequency link bidirectional DC transformer. Background technique [0002] With the development of power electronic control technology and device manufacturing technology, flexible DC transmission based on fully controlled voltage source converter (VSC) has achieved rapid development. Compared with the traditional DC transmission technology, flexible DC transmission does not have the problem of commutation failure, and can be applied to supply power to passive loads; using pulse width modulation (PWM) technology, the harmonic content of voltage and current is less, and the filtering link can be omitted. It makes the footprint smaller; the control is flexible, and the independent decoupling control of active power and reactive power can be quickly realized, and the fast reversal regulation o...

AI Technical Summary

Problems solved by technology

However, the addition of three semiconductor switches increases the cost of the switch by 37.5%, and the semiconductor switches S1 and S2 flow a current equivalent to the load current, resulting in increased loss, which reduces efficiency and power density to a certain extent

In addition, two and one semiconductor switches are added to the full bridge on the high and low voltage sides respectively, which reduces the modularity of the conversion unit to a certain extent.

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