A control method for ac-dc bidirectional conversion to improve system reliability

Abstract

The invention discloses a control method for improving system reliability through AC-DC bidirectional transformation. According to different states of rectification and inversion, a state zone bit Bg is set, where the value 1 of the Bg is high level, and 0 is low level. Vbus is defined to be high voltage, Vbat is defined to be low voltage, Vbus to Vbat is the AC / DC rectification state. When Bg=1, 1 is the high level and the 0 is the low level. Vbat to Vbus is the DC / AC inversion state. When Bg=0, judgment of Vbus voltage hardware detection is not shielded through the zone bit and when Bg=1, the judgment of Vbus voltage hardware detection is shielded. According to the invention, it is achieved that under the inversion mode, a pipe on the Vbat side of the low voltage side can be protected against damage in a conversion process from low voltage to high voltage, and ZCS cutoff is achieved on the pipe at the low voltage side, so cutoff loss is reduced, a Vds peak stress problem of the pipe caused by the cutoff is also eliminated and circuit EMC is improved.

Description

technical field [0001] The invention relates to a control method, in particular to a control method for improving system reliability by AC-DC bidirectional conversion. Background technique [0002] For the current energy storage and battery activation equipment, AC / DC bidirectional is already the current demand. Photovoltaic inverters can realize bidirectional flow of AC / DC energy, but they basically do not realize electrical isolation, which is not great for small and medium power applications. In order to achieve electrical isolation and obtain a more desired voltage, AC / DC bidirectional generally adopts two-stage conversion, one-stage AC→DC rectification, and the latter stage DC→DC isolation conversion. In the DC / DC isolation conversion topology, the LLC topology is the most applicable, and it can realize ZVS in almost the whole range, and there is also a fixed turn-off loss. [0003] The current AC / DC bidirectional converter uses a MOS tube as the switch tube. Its bidi...

AI Technical Summary

Problems solved by technology

[0003] The current AC / DC bidirectional converter uses a MOS tube as the switch tube. Its bidirectional conduction characteristics enable the circuit to realize AC / DC bidirectional conversion. The LLC topology in the DC / DC bidirectional converter is hard-off when the switch tube is turned off. , there are turn-off losses which cannot be avoided

In high and low voltage applications, such as high voltage conversion to low voltage, due to the large turn ratio, during AC / DC bidirectional conversion, that is, during DC / DC bidirectional conversion, when low voltage is converted to high voltage, the low voltage side is turned off. The current is very large, which causes a large Vds peak to the switching tube on the low-voltage side, and at the same time has a large turn-off loss, which greatly reduces the reliability of the circuit

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