A unidirectional direct current voltage conversion device and system and its control method

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 rear-stage switch circuit, a front-stage circuit, a front-stage auxiliary isolating switch, a rear-stage auxiliary isolating switch, and a main power circuit. Among them, the power main circuit is composed of a fully controlled H-bridge circuit, a high-frequency transformer, a resonant element, an uncontrolled H-bridge circuit and input / output capacitors, and the upper and lower bridge arms of each half-bridge of the uncontrolled H-bridge circuit adopt composed of multiple diodes connected in series. Combining pre-stage, post-stage switching circuits and isolating switches. The unidirectional DC voltage conversion device can use multiple units for free series and parallel combination to form a system, which has a wider application range for the voltage and current requirements of the load. At the same time, combined with the series diode technology, it can greatly reduce the single The number of used DC voltage conversion devices reduces the system cost and improves the power density of the conversion device.

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.

Images