Six-half-bridge space vector pulse width modulation (SVPWM) control method for high-voltage high-power three-phase asynchronous motor

Abstract

The invention relates to the variable-frequency speed regulation technology of a three-phase asynchronous motor and aims at providing a six-half-bridge space vector pulse width modulation (SVPWM) control method for a high-voltage high-power three-phase asynchronous motor. A frequency converter used in the method consists of a direct current power supply or a capacitor and six half bridges, two power supply terminals of each phase of the converter are respectively connected with two ends of each phase winding of a three-phase asynchronous motor stator, two groups of half bridges are respectively subjected to the traditional three-half-bridge no-dead-time voltage space vector modulation, modulation signals of each corresponding switch tube are obtained, the obtained modulation signals pass through a no-dead-time optimization process based on the principle of identical output average voltage in each corresponding switch period before and after the optimization, and in addition, the dead-time time is added at the each phase output current inverting part to obtain final modulation signals of each switch tube. The method has the advantages that only one dead time is provided during the phase current inversing in each half period, the dead-time adding frequency is twice of the reference voltage frequency, and the influence of the added dead time can be nearly ignored through being compared with that of the switch frequency.

Description

technical field [0001] The invention relates to the technical field of frequency conversion and speed regulation of high-voltage and high-power three-phase asynchronous motors, in particular to a SVPWM control method capable of expanding the voltage output range without dead zones. Background technique [0002] The voltage space vector pulse width modulation (SVPWM) technology has the characteristics of high voltage utilization, less switching times, and good harmonic suppression characteristics. It has been widely used in high-voltage and high-power asynchronous motor AC variable frequency speed control systems. Traditional three-half-bridge SVPWM technology, the maximum output phase voltage fundamental amplitude output range is the DC bus voltage E times, the voltage stress that each switching tube bears is the DC bus voltage E. [0003] Generally, when the power level of the three-phase asynchronous motor reaches several kilowatts or more, for the convenience of power s...

AI Technical Summary

Problems solved by technology

However, the disadvantage of this power supply is poor reliability. The two inverters need to work together, and the output voltage phase of the two inverters must be strictly different from each other by π electrical angle. Once a certain inverter fails to work normally, it will directly cause the asynchronous motor to fail to work normally.

In addition, the working mode of the upper and lower switching tubes of each half-bridge of the two inverters is complementary conduction, so it is inevitable to introduce a dead zone

Due to the addition of dead time, it will inevitably lead to an increase in the harmonic content of the output voltage, and will cause a certain drop in the output voltage

Although many scholars have proposed dead zone compensation schemes, it is impossible to completely solve the impact of the dead zone, and it will definitely make the control more complicated.

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