A unidirectional DC voltage conversion device and system and a control method thereof

Abstract

The invention discloses a unidirectional DC voltage conversion device and system and a control method thereof. The unidirectional DC voltage conversion device is composed of a front-stage switch circuit, a back-stage switch circuit, a front-stage circuit, a front-stage auxiliary isolation switch, a back-stage auxiliary isolation switch and a power main circuit. The main power circuit consists of afully controlled H-bridge circuit, a high-frequency transformer, a resonant element, an uncontrolled H-bridge circuit and an input / output capacitor. The upper and lower arms of each half-bridge of the uncontrolled H-bridge circuit are composed of a plurality of series diodes. Combine the front and back switching circuits and isolation switches. The one-way direct current voltage conversion devicecan adopt multiple units to combine freely in series and parallel, Combined with series diode technology, it can greatly reduce the number of unidirectional DC voltage converter, reduce the cost of the system and increase the power density of the converter in high voltage system.

Description

technical field [0001] The invention belongs to the field of power electronics applications, and specifically relates to a unidirectional DC voltage conversion device and system and a control method thereof, and is especially suitable for applications such as photovoltaic and other new energy DC grid-connected, ice-melting devices, and the like. Background technique [0002] As an important component of DC power grids, DC voltage conversion devices have attracted more and more attention from scholars in the field of DC power grids. In order to realize the power conversion of the medium / low voltage to high voltage DC bus, due to the influence of the stress and cost of the switch tube device, it is easy to use multiple isolated DC voltage conversion devices, each device is used as a sub-unit, and its high-voltage ports are connected in series, After the low-voltage ports are connected in parallel (ISOP or IPOS structure), it is applied to occasions with higher voltage levels a...

AI Technical Summary

Problems solved by technology

[0004] However, with the development of photovoltaic new energy and other DC grid-connected requirements, in order to reduce line loss and realize longer transmission distance and transmission capacity of photovoltaic power generation, the system voltage level is continuously improved, but the voltage tolerance of a single device is certain. In order to meet the application of higher voltage levels, the high-voltage side of the existing DC voltage conversion device needs to be equipped with more series sub-modules, which will not only reduce the reliability of the system, increase the cost of the system, but also make the control strategy of the system more complicated

[0005] In addition, for some specific applications, such as using a unidirectional DC voltage conversion device to melt ice on a DC line, the length of the ice-melting line is uncertain, the equivalent load resistance is uncertain, and the operating range of the device is higher.

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