Neutral-point voltage balance and common-mode voltage suppression method for three-level inverter

Abstract

The invention relates to a neutral-point voltage balance and common-mode voltage suppression method for a three-level inverter, and mainly provides a novel visual space vector modulation (VSVM) method. The method comprises the following steps: defining a new visual zero vector to just include zero vector 000; defining a novel visual small vector to be composed of an original negative small vector and two negative small vectors adjacent to the original negative small vector; and defining a new visual medium vector to be composed of an original medium vector and two medium vectors adjacent to the original medium vector. By using the space vector definition method, each composite vector cannot cause neutral-point voltage to be fluctuated, and basic vectors forming the novel visual space vector do not include positive small vectors and zero vector PPP and NNN, so that the output common-mode voltage is relatively small. When external nonlinear factors enable the neutral-point voltage to be fluctuated, on the basis of a new visual space vector modulation strategy, the action time distribution factors for each composite vector are appropriately adjusted by comparing the size of three-phase load current, so that neutral-point voltage balance is controlled.

Description

technical field [0001] The invention relates to a three-level inverter control strategy, in particular to a method for neutral point voltage balance and common-mode voltage suppression of a three-level inverter. Background technique [0002] In order to ensure the long-term reliable and stable operation of the multilevel NPC inverter, it is necessary to ensure the neutral point voltage balance. In recent years, the problem of midpoint voltage balance has been widely concerned by scholars at home and abroad. Its control strategies mainly include the following types: (1) Carrier sinusoidal PWM injected with zero-sequence components; (2) Based on specific harmonic elimination PWM, by fine-tuning the specific harmonic elimination PWM switching angle to change the action time of the zero state to achieve control point voltage; (3) based on space vector PWM (Space Vector Modulation, SVM), the control of the midpoint voltage is realized by controlling the vector action time distri...

AI Technical Summary

Problems solved by technology

Existing studies rarely consider the balance of the mid-point voltage when suppressing the common-mode voltage. If the mid-point voltage fluctuates greatly, the amplitude of the common-mode voltage will also change accordingly, resulting in a greater impact on the output waveform.

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