Cascaded two-level inverter SVPWM modulation method based on dodecagonal space voltage vectors

Abstract

The invention discloses a cascaded two-level inverter SVPWM modulation method based on dodecagonal space voltage vectors. First and second three-phase two-level inverters which are cascaded are comprised. The method comprises the steps that 1 a dodecagonal space voltage vector distribution map is constructed; 2 which sector in which a reference voltage vector Uref is located in twelve sectors of the dodecagonal space voltage vector distribution map is determined; 3 two non-zero voltage vector action times T1 and T2 and a zero voltage vector action time T0 in the area are calculated; 4 a spacevoltage vector switching point is calculated; and 5 switch positions corresponding to the voltage vectors are determined, and according to the principles of waveform symmetry and the minimum number oftimes of switch, the SVPWM waveform of the sector is determined. According to the invention, the output phase voltage amplitude is increased by 3.6% compared with hexagonal space voltage vector pulsewidth modulation; the direct current bus voltage utilization rate is increased by 11.5%; the phase voltage output by the inverters does not contain (6n+/-1) harmonics; and harmonic distortion is significantly improved.

Description

technical field [0001] The invention relates to a space voltage vector modulation method, in particular to a SVPWM modulation method of a cascaded two-level inverter based on a dodecagonal space voltage vector. Background technique [0002] With the continuous improvement of power electronics technology and the continuous improvement of the performance of semiconductor devices, multi-level inverters are widely used in high-power dragging variable-frequency speed-regulating motor loads, long-distance high-voltage transmission lines, and high-power equipment with high power quality requirements. And many other aspects. Cascaded inverter is a special form of multi-level inverter, and it is more and more widely used in fields such as motor control, reactive power compensation, and harmonic control. [0003] The modulation method of the cascaded inverter has always been a hot and difficult point of research. Different modulation methods make the cascaded inverter have different ...

AI Technical Summary

Problems solved by technology

At present, the PWM control methods of cascaded inverters mainly include sinusoidal pulse width modulation SPWM and space vector pulse width modulation SVPWM. SVPWM is significantly better than SPWM in terms of DC power utilization and low current ripple, but in the In multilevel inverter topologies with boundary voltage vectors, the fifth and seventh harmonics appear in the overmodulation region, and the resulting harmonic currents limit the bandwidth of the proportional-integral controller

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