Rapid frequency-superposed braking control method for high-voltage frequency converter

Abstract

The invention relates to a rapid frequency-superposed braking control method for a high-voltage frequency converter, and belongs to the field of power electronics and electrical transmission control.The adopted method comprises the steps that a deceleration instruction is extracted according to the variable quantity given by the target rotating speed, a voltage-frequency curve is adjusted, and smooth transition of the voltage-frequency curve is achieved through slope output according to given voltage. 250Hz positive-sequence or negative-sequence voltage is injected in the given direction of the rotating speed, double closed-loop control of direct-current bus voltage and motor current modulus is adopted, a given value of the direct-current bus voltage is set between a no-load bus voltage value and an overvoltage protection value, PI adjustment is conducted on the given value of the direct-current bus voltage and an actual value of the direct-current bus voltage, and output of an adjuster serves as a frequency-superposed current given value; and then proportional adjustment is performed with a motor current module value, and the output of the regulator is used as a frequency-superposed voltage given value. After the target rotating speed is reached, the modulation degree is smoothly transited to the initial voltage frequency curve, and the braking process is completed.

Description

technical field [0001] The invention belongs to the field of power electronics and electric transmission, and relates to a fast overlapping frequency braking control method of a high-voltage frequency converter. Background technique [0002] The high-voltage inverter adopts the H-bridge power unit cascade topology, and the output voltage ranges from 3kV to 10kV. It has the advantages of low output voltage harmonics, simple control and high cost performance. It is widely used in fan, water pump and other process speed regulation and energy saving occasions. However, the application of high-voltage inverters is also limited, and the topology structure determines that its braking performance is greatly limited. In the occasions with high requirements on braking performance such as mine hoists and belt conveyors, four-quadrant high-voltage inverters need to be used, and there are problems such as complex systems, many fault points and high prices. In order to avoid using the fo...

AI Technical Summary

Problems solved by technology

However, the application of high-voltage frequency converters is also limited, and the topology determines that its braking performance is greatly limited.

In the occasions that have high requirements on braking performance, such as mine hoists and belt conveyors, four-quadrant high-voltage inverters are required, and there are problems such as complex systems, many fault points, and high prices.

In order to avoid the use of four-quadrant high-voltage inverter solutions, some manufacturers at home and abroad try to improve the braking performance of high-voltage inverters by using the overlapping frequency braking method, which reduces the braking time by 40%. The control method mostly adopts fixed-frequency and fixed-amplitude open-loop control , the superimposed frequency braking power cannot be adjusted. In order to adapt to different working conditions, the superimposed frequency power must be much greater than the mechanical power, and there are defects such as large energy consumption and large bus voltage fluctuations.

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