Low-voltage precharging system for high-voltage variable frequency system, and control method of low-voltage precharging system

Abstract

The invention discloses a low-voltage precharging system for a high-voltage variable frequency system, and a control method of the low-voltage precharging system. The low-voltage precharging system comprises a high-voltage power supply, a high-voltage switch, a transformer, a low-voltage power supply and a low-voltage precharging circuit, wherein an input end of the high-voltage switch receives the high-voltage power supply; a primary side of the transformer is connected with an output end of the high-voltage switch; a secondary side of the transformer is connected with the high-voltage variable frequency system; an input end of the low-voltage precharging circuit receives the low-voltage power supply; an output end of the low-voltage precharging circuit is connected with a low-voltage winding of the transformer; and the low-voltage precharging circuit comprises a precharging switch, a precharging resistor connected in series with the precharging switch, a maintaining resistor connected in series with the precharging resistor, and a bypass switch connected in parallel with the maintaining resistor. Compared with a high-voltage precharging circuit, the low-voltage precharging system can greatly lower the product cost; the space volume of the system can be reduced effectively; impact of short-circuit current on a power supply system can be limited; and the power consumption of the precharging resistor can be reduced effectively.

Description

technical field [0001] The invention relates to the technical field of power electronics and high-voltage frequency conversion, in particular to a low-voltage pre-charging system used in a high-voltage frequency conversion system and a control method thereof. Background technique [0002] With the development of power electronics technology and the in-depth research on high-voltage inverter technology, high-voltage inverters are widely used in the drive systems of high-power mechanical equipment such as fans, water pumps, and compressors. [0003] There are energy storage elements such as capacitors in the high-voltage frequency conversion system. When the high-voltage switch is closed, an excitation surge current several times the rated current of the frequency conversion system will be generated. This excitation surge current will have a huge impact on the power frequency grid and the high-voltage frequency conversion system. , In serious cases, it will affect the normal s...

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Problems solved by technology

[0005] However, the cost of the high-voltage contactor (high-voltage switch) and high-voltage pre-charging resistor used in the prior art is relatively high, and the space occupied by it is relatively large. Therefore, this pre-charging scheme has become the key to restricting the effective cost control of high-voltage frequency conversion products. one of the factors

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