Bidirectional DC/DC converter and modulation method thereof

Abstract

The invention provides a bidirectional DC / DC converter and a modulation method thereof, and the method comprises the steps: determining the voltage difference between two sides according to the detected high-voltage side voltage and low-voltage side voltage of the bidirectional DC / DC converter, and controlling the modulation mode of the bidirectional DC / DC converter to be switched from single-stage modulation to double-stage modulation after the voltage difference between the two sides is judged to be in a preset voltage difference range, namely when voltages at the two ends are close or consistent, two-stage modulation is used for replacing single-stage modulation, the problem that the modulation degree of single-stage modulation is too large is avoided, the duty ratio is prevented from being lost, inductor charging and discharging energy is balanced, input and output current ripples are small, stable modulation of the bidirectional DC / DC converter in a full-voltage range section canbe achieved, the waveform quality of currents is improved, and the stability of the system is improved.

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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