Pre-charging device and method of high-voltage frequency converter

Abstract

The invention discloses a high-voltage inverter pre-charging device and method, including a pre-charging circuit system and a pre-charging switching system; the pre-charging circuit system includes a pre-charging main circuit unit and a pre-charging control circuit unit; the pre-charging main The input end of the loop unit is connected to the low-voltage AC power supply, and the output end of the pre-charging main loop unit is connected to the DC bus capacitor of the high-voltage inverter; the pre-charging control loop unit is used to detect the final output DC voltage of the pre-charging main loop unit , according to the detected DC voltage to control the output voltage of the inverter in the pre-charging main circuit unit; the pre-charging switching system is used to detect the voltage at both ends of the DC bus capacitor of the high-voltage inverter, and send the detection signal to the inverter Control system: The frequency converter control system controls the pre-charging circuit system to cut out, controls the high-voltage switch of the frequency converter to close, or controls the pre-charging circuit system to cut in, and controls the high-voltage switch of the frequency converter to open according to the received signal.

Description

technical field [0001] The invention relates to the technical field of high-voltage frequency converters, in particular to a pre-charging device and method for high-voltage frequency converters Background technique [0002] With the development of power electronics technology, as a product of the development of power electronics technology, frequency converters have been widely used in various fields of the national economy, such as metallurgy, petrochemical, municipal, electric power and other industries, and are playing an increasingly important role. Yes, the application of high-voltage and high-power inverters is becoming more and more extensive. Among the high-voltage inverters, the high-voltage and high-power inverters composed of power modules connected in series are favored by many inverter manufacturers, scientific research institutes, engineering and technical personnel, and users as inverters that are suitable for China's national conditions and have excellent per...

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Problems solved by technology

Although this method can realize the charging of the frequency converter with a low-voltage power supply, there are still some problems, mainly because the rated capacity of the rectifier transformer is much larger than the rated capacity of its auxiliary winding, so when the auxiliary winding is excited, the steady-state excitation The current is very large. Excessive excitation current will cause an excessive voltage drop on the current limiting resistor. If fewer contactors are selected, the resistance value of each bypass is large, and each bypass is suddenly added to the auxiliary current. The voltage on the winding is relatively high, so every time a contactor is used to bypass the resistance, a large impact current will be generated on the low-voltage power supply, and it will also have a certain impact on the DC capacitor in the power unit. If more contactors are selected, Then the cost is higher; secondly, if in order to save costs, the last stage contactor is omitted, and the current limiting resistor used is not bypassed before disconnecting the charging circuit, then the pre-charging is not sufficient considering the voltage drop on the resistor , there will still be an inrush current when the high voltage is powered on; finally, due to the excessive excitation current, the resistor will be seriously heated, so this circuit needs to use a high-power resistor, which is large in size, high in cost and low in efficiency.

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