A switching method between high-voltage variable frequency and power frequency

Abstract

The invention discloses a high-voltage variable frequency and power frequency switching method, which comprises the steps of 1) connecting a high-voltage frequency converter to a load motor, starting the high-voltage frequency converter so as to supply power to the load motor, and getting into a variable-frequency power supply mode; 2) switching the variable-frequency power supply mode into a power-frequency power supply mode, connecting a power-frequency power grid to the load motor, blocking pulses of the high-voltage frequency converter, disconnecting the high-voltage frequency converter after the pulses are blocked, and supplying power to the load motor by the power-frequency power grid and the high-voltage frequency converter simultaneously after the power-frequency power grid is connected and before the pulses are blocked; and 3) switching the power-frequency power supply mode into a variable-frequency power supply mode, starting the high-voltage frequency converter, connecting the high-voltage frequency converter to the load motor when running to the power frequency, disconnecting connection between the power-frequency power grid and the load motor, supplying power to the load motor by the power-frequency power grid and the high-voltage frequency converter simultaneously after the high-voltage frequency converter is connected and before the power-frequency power grid is disconnected, and returning back to the step 2). The method disclosed by the invention has the advantages of simple implementation method, stable system operation, and ability of realizing two-way switching between the power frequency and the variable frequency without power loss switching time.

Description

technical field [0001] The invention relates to the field of motor control, in particular to a method for switching between high-voltage frequency conversion and power frequency. Background technique [0002] Since the invention of the AC motor, it has been widely used in mining, petrochemical and other fields due to its simple structure, high reliability and excellent drag performance. However, due to the inherent starting characteristics of AC motors, the starting current during direct starting can be up to 15 times the rated current of the motor, which will generate a large inrush current to the power grid. Soft start technology came into being under this background. The soft start technology of the motor has been applied and developed for many years, and a variety of technical solutions have been produced. The traditional technical solutions include star-delta conversion soft start, autotransformer soft start, and saturated reactor soft start. Level, in the conversion p...

AI Technical Summary

Problems solved by technology

[0006] (1) If the control method of power-off switching is adopted, the load motor may generate a large current impact during the power-off switching process due to the long power-off time;

[0007] (2) There is no effective measure to suppress the current impact of the soft start process

This scheme adopts the control method of power-off switching. The motor may generate a large current impact during the power-off process due to the long power-off time, and there are certain difficulties and technical risks.

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