A combined high-voltage DC circuit breaker with DC power flow control capability and its control strategy

Abstract

The invention discloses a combined high voltage DC circuit breaker with DC power flow control and a control strategy thereof. The daily flow passage branch of the traditional combined high voltage DC circuit breaker is improved, a load transfer switch is changed from the original IGBT series into the full bridge sub-module series, and an overvoltage energy drain branch is additional provided. The invention controls the size of the positive resistance effect in the branch by controlling the frequency of the load transfer switch sub-module capacitor, so as to realize the purpose of the power flow control. Compared with the prior art, the load transfer switch of the circuit breaker topology of the invention has the dual function of the circuit breaker and the power flow controller, so as to reduce the repeated investment and reduce the construction cost of the power grid. In addition, the IGBT obtains power directly from the sub-module capacitor thereof while the external power supply is not required, the insulation problem difficult to solve in the project is avoided, and the application prospect in the high voltage DC power grid is enhanced.

Description

technical field [0001] The invention belongs to the technical field of power electronic systems, and in particular relates to a combined high-voltage direct current circuit breaker with direct current flow control capability and a control strategy thereof. Background technique [0002] The DC power grid is one of the important directions for the future development of my country's power grid. Compared with the traditional two-terminal DC transmission system, the DC power grid has the following advantages: (1) The economy of the system operation is greatly enhanced, and the traditional point-to-point transmission is changed to networked transmission. , reducing the number of converter stations required by the DC system, not only reducing the area occupied by the converter stations, saving transmission corridor resources, but also reducing the overall transmission loss of the system and reducing the difficulty of controlling the DC network; (2) The operating flexibility of the sy...

AI Technical Summary

Problems solved by technology

For this reason, several implementation forms of DC power flow controllers have been proposed in the literature, but this kind of power flow controller needs to add additional power electronic equipment, which increases the cost of the DC power grid.

[0006] In addition, both the DC circuit breaker and the DC power flow controller need to be connected in series in the DC line. At present, the external power supply is mainly used to supply the drive circuit of the IGBT in the device. Due to the high voltage level, it is difficult to achieve the insulation and withstand voltage indicators of the external power supply circuit. This defect greatly limits the application of DC power grid technology in the field of high voltage technology.

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