A three-level space vector modulation method

Abstract

The invention relates to a three-level space vector modulation method, which divides the entire space vector diagram into six large areas A-F, each of which is similar in nature, and divides the 27 basic vectors of the three-level inverter according to the modulus length Divided into 6 large vectors, 6 medium vectors, 6 pairs of positive and negative small vectors, and 3 zero vectors, and designed a new virtual medium vector VNMi=kA0VMi+kA1VSi+kA2VS(i+1)(i=0 ,1,2...5); use the gh coordinate system in the new space vector diagram, and use a simple logical judgment method to calculate the vector partition and vector action time; the reference vector is synthesized from the latest three new space vectors . The present invention proposes a new space vector definition method, so that when the reference vector is located in any area of ​​the space vector diagram, its composite vector contains two paired positive and negative small vectors, which can avoid some problems in the traditional space vector modulation method. The problem that the midpoint voltage in some areas cannot be completely balanced.

Description

technical field [0001] The invention relates to a three-level inverter modulation method, in particular to a new three-level inverter space vector pulse width modulation (Space Vector PWM, SVPWM) method. Background technique [0002] With the advancement of science and technology, the requirements for the quality of inverter output power and output power are constantly increasing, and multi-level converters are increasingly used in fields such as industry and social life to provide better quality power and higher Output Power. [0003] The SVPWM modulation method starts from the perspective of how to make the motor obtain a circular magnetic field with a constant amplitude, based on the ideal magnetic flux of the AC motor when the three-phase symmetrical sinusoidal voltage is supplied, and the actual magnetic flux generated by the different switching modes of the inverter. By approaching the reference flux circle, the switching state of the inverter is determined by the com...

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Problems solved by technology

[0004] However, when the traditional SVPWM method is used in a multi-level diode-clamped inverter, there are no pairs of small vectors to participate in the synthesis of reference vectors when the modulation degree is large, so the control of the midpoint voltage cannot be effectively realized.

And in some areas with a large modulation degree in the space vector diagram, there is no or only one pair of positive and negative small vectors in the basic vectors participating in the synthesis. While controlling the balance of the midpoint voltage, there is no redundant pairing Small vector to achieve other control objectives

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