Combined-type SVPWM method

Abstract

The invention discloses a combined-type SVPWM (Space Vector Pulse Width Modulation) method. Different SVPWM methods are adopted according to different stator frequencies of an AC motor; when the stator frequency of the AC motor is lower than the low-frequency sector, a half-frequency method is adopted; when the stator frequency of the AC motor is in the medium-and-low frequency sector, a flat-top SVPWM method is adopted; when the stator frequency of the AC motor is in the medium-and-high frequency sector, a seven-segment SVPWM method is adopted; and when the stator frequency of the AC motor is in the high-frequency sector, an FFC (Fundamental Frequency Clocking) SVPWM method. Usually, for power loss of an inverter, the seven-segment SVPWM method is larger than the flat-top SVPWM method, the flat-top SVPWM method is larger than the half-frequency SVPPWM method, and the half-frequency SVPPWM method is larger than the FFC SVPWM method; and for the torque control precision, the four methods are optimal within different frequency ranges. According to the invention, the four SVPWM method are used together, different SVPWM methods are adopted according to different working conditions of the motor so as to play respective potentials; and therefore, lower power loss of the inverter and higher torque control precision are drawn into consideration, and the output power of the motor running in the high-frequency sector is increased.

Description

technical field [0001] The present application relates to a control method of an AC motor, in particular to a SVPWM (space vector PWM, voltage space vector pulse width modulation) method. Background technique [0002] SVPWM is a control method for AC motors. This method considers the inverter and the AC motor as a whole, and no longer sticks to making the output voltage of the inverter as close as possible to the three-phase symmetrical sine wave, but focuses on making the AC The motor tries to form a circular flux linkage trajectory, and uses this as a goal to control the switching state of the inverter to form a PWM waveform. [0003] Commonly used SVPWM methods include seven-segment SVPWM, Flat-Top SVPWM, half-frequency SVPWM, FFC (Fundamental Frequency Clocking) SVPWM, and the like. [0004] see figure 1 , which is a schematic diagram of a three-phase inverter powering an AC motor. The three-phase inverter has three bridge arms A, B, and C, and each bridge arm is comp...

AI Technical Summary

Problems solved by technology

[0021] First, large inverter losses will make the motor drive system inefficient, which will affect the range of electric vehicles

[0022] Second, the high loss of the inverter will also generate relatively high heat, resulting in excessive heat dissipation load of the cooling system of new energy vehicles

Considering that the actual cooling capacity of the inverter is limited, in order to prevent the inverter from generating a lot of heat, it is necessary to limit the current flowing through the inverter so that it cannot be too large, thus limiting the current output capability of the inverter

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