A kind of bidirectional dc/dc converter and its modulation method

Abstract

The present invention provides a bidirectional DC / DC converter and a modulation method thereof. According to the detected high-voltage side voltage and low-voltage side voltage of the bidirectional DC / DC converter, the voltage difference on both sides is determined, and the voltage difference on both sides is judged to be at a preset value. After the voltage difference range, the modulation mode of the control bidirectional DC / DC converter is switched from single-level modulation to dual-level modulation; that is, when the voltages at both ends are close to or consistent, dual-level modulation is used instead of single-level modulation to avoid single-level modulation down-regulation The system is too large to prevent the loss of duty cycle, so that the charge and discharge of the inductor can be balanced and the input and output current ripple is small, and the stable modulation of the bidirectional DC / DC converter in the full voltage range can be realized, and the current waveform is improved. quality, and improved system stability.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a bidirectional DC / DC converter and a modulation method thereof. Background technique [0002] The topology of a bidirectional DC / DC converter is as follows figure 1 As shown, in the prior art, single-stage modulation is usually used to control the operation mode of the bidirectional DC / DC converter, that is, chopping control is performed on the high voltage side, the outer tube is turned on and the inner tube is turned off at the low voltage side. When the current flows from the high-voltage side to the low-voltage side, it operates in the buck mode, that is, the step-down mode; when the current flows from the low-voltage side to the high-voltage side, it operates in the boost mode, that is, the boost mode; bidirectional buck-boost free switching. [0003] The above single-stage modulation method can operate stably and efficiently under most working conditions. Howeve...

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Problems solved by technology

[0003] The above single-stage modulation method can operate stably and efficiently under most working conditions. However, if the voltage at both ends of the bidirectional DC / DC converter is the same or the voltage difference is less than a certain value, the modulation will be too large, resulting in the emptying of the inner tube. The ratio is lost, and there is an out-of-control area, which will lead to large input and output current ripples, resulting in lower power quality and system oscillation when multiple machines are running in parallel.

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