A frequency converter integrated braking system and its working method

Abstract

The invention discloses an integrated brake system for a converter and a working method of the integrated brake system. The integrated brake system for the converter is characterized by comprising theconverter and an AC brake unit, wherein an output end of the converter is connected with a motor; the AC brake unit is connected to the output end of the converter; in the braking process of the motor, the AC brake unit and the converter cooperatively work and generate braking torque at the same time or in a time-sharing manner; the integrated brake system for the converter comprises three working modes: an AC brake mode, an integrate brake mode and a variable-frequency brake mode in the braking process of the motor; when the integrated brake system for the converter is in the AC brake mode,the AC brake unit generates the braking torque and the converter does not generate the braking torque; when the integrated brake system for the converter is in the integrated brake mode, the AC brakeunit and the converter generate the braking torque; and when the integrated brake system for the converter is in the variable-frequency brake mode, the AC brake unit does not generate the braking torque.

Description

technical field [0001] The invention relates to a frequency converter braking system and its working method, and in particular discloses a frequency converter comprehensive braking system and its working method, which are applied in the field of motor frequency conversion drive. Background technique [0002] When using a frequency converter to drive the motor, if the motor needs to brake quickly, there are two commonly used solutions: Option 1 uses a frequency converter to achieve fast braking, such as adding chopper braking to the DC side of the frequency converter or using an active front-end rectifier ;Scheme 2 connects an AC switch and a resistor at the motor end, which is usually used for braking of a synchronous motor. When the motor brakes, close the AC switch, put the resistor in, and the motor is in the state of generating power. When it is used to excite a synchronous motor, it can also control the power absorbed by the AC resistance by controlling the motor termin...

AI Technical Summary

Problems solved by technology

These two schemes have their own advantages and disadvantages: scheme 1 can achieve constant power braking during the entire deceleration process, and can still provide sufficient braking torque when the motor speed is low, but if scheme 1 uses active front-end rectification , the system is complex and the cost is high; if DC chopper braking is used, the energy consumption will be large. In addition, when the frequency converter does not have a centralized DC bus, such as the unit series multi-level topology frequency converter, each DC chopper braking is added to the power unit. In the application of high-power braking, the structure of the power unit is complicated and not practical.

Scheme 2 adopts centralized AC resistance braking, which does not require additional components of the inverter. The system structure is simple and is applicable to all inverter topologies. However, the braking torque of Scheme 2 is directly related to the motor terminal voltage, while the motor terminal voltage is directly related to the The speed of the motor is related. When the speed of the motor is low, it cannot provide enough braking torque, and the deceleration time is difficult to guarantee.

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