Control method for overmodulation of variable frequency motor

Abstract

The invention relates to an air conditioner control technology, and provides a control method for overmodulation of a variable frequency motor, and the control method is used for solving the problems that a vector control method is quite high in calculated amount and control errors are prone to occurring. Firstly, the duty ratio is calculated out by a system according to the fundamental current amplitude of reference voltage and DC bus voltage values, secondly, the normalization value of control voltage on DC bus voltage is calculated out by the system according to the control voltage and the DC bus voltage, then, the correspondence of the duty ratio and the normalization value is set up by the system and stored, and finally, three-phase voltage control time is calculated out by the system to control operation of the motor according to the correspondence of the duty ratio and the normalization value. A vector control technical framework, especially a linear region modulation control and overmodulation control technical framework is rebuilt from a brand new angle, action time of the zero vector and the like does not need to be calculated, a calculating method is simplified, and calculating time is shortened. The control method is suitable for overmodulation control over the variable frequency motor.

Description

technical field [0001] The invention relates to the air conditioner control technology, in particular to the overmodulation control of the variable frequency motor. Background technique [0002] The traditional variable frequency motor vector control method, according to the on / off combination method of the upper and lower bridge backs of 6 inverters, forms 8 vectors, the two vectors corresponding to the upper and lower bridge backs are fully open and fully closed are zero vectors, and space vector synthesis is used The method is calculated to control the PWM of the six bridge backs to control the operation of the motor. Dividing a cycle into 6 sectors yields 8 vectors including two zero vectors, as in figure 1 As shown, in each sector, use two adjacent non-zero vectors and the corresponding zero vector to synthesize any vector in the sector, and thus calculate the action time T0 of the two adjacent non-zero vectors and the zero vector . Patent 2 0 0 8 1 0 1 0 1 4 9 7.0 (...

AI Technical Summary

Problems solved by technology

[0004] However, the vector control method needs to record and distinguish the positions of the six working sectors where the current vector is located, and the control theory is complicated and difficult to understand, with a large amount of calculation. The derivation of the control theory in the over-modulation area is more complicated and difficult to understand, and the control methods are various. In the same way, the control results are quite different, and control errors are prone to occur

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