Compensation method for pulse width modulation dead zone in three-phase grid-connected converter

Abstract

The invention discloses a compensation method for a pulse width modulation dead zone in a three-phase grid-connected converter. The compensation method has the advantages that the compensation method can solve the mis-compensation phenomenon caused by the oscillation of current in the vicinity of passing zero point, realize the real-time compensation for the dead zone and significantly improve the wave quality of the output current. The compensation method judges the dead-zone compensation phase and the dead-zone compensation direction by theta e which is defined by the invention, determines the compensation voltage amount by t'e which is defined by the invention, then determines the final three-phase voltage control amount by combining the dead-zone compensation phase, the dead-zone compensation direction and the compensation voltage amount, and controls the three-phase grid-connected converter to transmit the power to a grid by a digital signal processor according to the three-phase voltage control amount.

Description

technical field [0001] The invention relates to the technical field of pulse width modulation, in particular to a compensation method for a pulse width modulation dead zone in a three-phase grid-connected converter. Background technique [0002] At present, the vast majority of three-phase grid-connected converters adopt a three-phase six-tube bridge structure. In order to prevent the phenomenon of the same bridge arm from appearing when the three-phase grid-connected converter is working, it is necessary to The pulse width modulation signal (PWM) of the upper and lower switching tubes is added to the dead time, that is, in a switching cycle, the switching tube is turned off first during the switching process, and then the complementary switching tube is turned on. During this time, the two switches of a bridge arm are not turned on, forming a dead time. During this period, due to the existence of the inductor current, the switching device must maintain a certain freewheeli...

AI Technical Summary

Problems solved by technology

The authorized announcement number is CN1229909C, and the invention patent titled compensation method for dead zone of pulse width modulation type frequency conversion technology determines the direction of dead zone compensation according to the direction of sampling phase current, and in the power circuit, because the switching tube There is a lot of EMI interference during the turn-on and turn-off process, so there will be oscillation near the zero-crossing point of the phase current, resulting in multiple zero-crossing phenomena

The use of current filtering will introduce factors such as phase lag, which is not conducive to dead zone compensation

Because the oscillation of the phase current near the zero-crossing point will directly lead to the wrong judgment of the phase current direction, and the wrong judgment of the phase current direction will directly lead to the wrong judgment of the direction of the dead zone compensation, so the oscillation phenomenon of the phase current near the zero-crossing point makes the authorization The method provided by the invention patent with the notification number CN 1229909C has a false compensation phenomenon caused by the oscillation of the phase current near the zero-crossing point. This false compensation phenomenon makes the error voltage more enlarged, which leads to further deterioration of the current waveform and will cause Oscillations are formed near the zero crossing of the phase current

And the authorized announcement number is CN 100388610C, and in the invention patent named as UPS inverter and its pulse width modulation dead zone compensation method, a fixed value is used to compensate the dead zone. ) non-ideal operating characteristics, so that the influence of the dead zone on the output voltage will vary with the magnitude of the operating current. Therefore, the use of a fixed-time compensation method often results in false compensation

Whether it is the patent with the authorized announcement number of CN 1229909C, the patent with the authorized announcement number of CN 100388610C, or other existing technologies, it has not been able to make an accurate judgment on the determination of the dead zone compensation time, and has not performed real-time compensation for the dead zone.

Images