Three-phase inverter dead band time online adjustment and compensation method

Abstract

The invention discloses a three-phase inverter dead band time online adjustment and compensation method. By adjusting the dead band time online and modulating the dead band voltage into synthesized voltage of fundamental wave and third-harmonic square wave, the influence of harmonic voltage caused by a dead band on current is eliminated. The defect that the dead band time is close to zero when the current crosses zero is overcome. Moreover, current direction detection is not needed, calculation is simple, implementation is easy, and the method has engineering practical value.

Description

technical field [0001] The invention relates to the technical field of power electronic circuit control, in particular to an online adjustment and compensation method for the dead time of a three-phase inverter. Background technique [0002] The three-phase voltage source inverter (VSI) has been widely used now. Its commutation is completed between the upper and lower switching devices of the same bridge arm. The driving signal adopts complementary PWM signals. shutdown takes some time, and usually t off >t on , so there may be a phenomenon that the upper and lower switching devices are turned on at the same time (that is, one is not completely closed while the other is already open). Such as figure 1 As shown, when the upper and lower switching devices of the same phase bridge arm are turned on at the same time, it will cause a short circuit of the DC side power supply. In order to prevent this phenomenon, a certain time interval is usually added between the conducti...

AI Technical Summary

Problems solved by technology

[0002] The three-phase voltage source inverter (VSI) has been widely used now. Its commutation is completed between the upper and lower switching devices of the same bridge arm. The driving signal adopts complementary PWM signals. shutdown takes some time, and usually t off >t on , so it is possible that the upper and lower switching devices are turned on at the same time (that is, one is not completely closed and the other is already open)

[0003] The setting of the dead time will bring some negative effects to the inverter system, which will lead to output voltage and current distortion, which is not allowed in the occasions requiring high control performance, so it is necessary to compensate the dead time

[0004] In the existing methods, some methods are to calculate the error voltage vector caused by the dead zone and then compensate the error, but it is necessary to judge the direction of the current

Some methods use space vector modulation without dead zone, but this method needs to accurately obtain the current direction, and when the current is close to 0, due to PWM noise, current clamping effect, etc., it becomes very difficult to accurately detect the current zero crossing point. makes this method no longer effective near 0 current

There is also an adaptive online compensation method, which uses the difference between the given voltage and the estimated voltage to compensate the error voltage caused by the dead zone and the voltage drop of the switching tube, but the estimation algorithm depends on the motor parameters controlled by the inverter , and the calculation is complicated, so it is not suitable for engineering application

Images