Three-level space vector modulation method

Abstract

The invention relates to a three-level space vector modulation method. A whole space vector diagram is divided into six big regions from A to F, wherein the big regions have similar properties; 27 basic vectors of the three-level inverter are divided into six big vectors, six middle vectors, six pairs of positive and negative small vectors and three zero vectors according to the module length; a new virtual middle vector is designed, wherein V<NMi>=k <A0>V+k<A1>V<Si>+k<A2>V<S(i+1)> (i = 0, 1, 2 until 5); a gh coordinate system is applied to the new space vector diagram; vector partitioning and vector action time calculation are carried out by a simple logic judgment method; and a reference vector is synthesized by three latest new space vectors. The invention provides the new space vector defining method; when the reference vector is positioned in any region of the space vector diagram, the obtained resultant vector comprises a positive small vector and a negative small vector in pairs; and the problem that the neutral-point voltage in certain regions cannot be fully balanced in the conventional space vector modulation method can be avoided.

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 (SpaceVectorPWM, 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 compa...

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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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