A zero-common-mode modulation method suitable for mmc

Abstract

The invention discloses a zero-common-mode modulation method suitable for modular multilevel inverters, which includes: adjusting the carrier signal, the rising edge comparison value of PWM and the falling edge comparison value of PWM, so that each switch The first part of the PWM pulse signal of the upper bridge arm of the b-phase is connected with the tail of the PWM pulse signal of the upper bridge arm of the a-phase in the period, the first part of the PWM pulse signal of the upper bridge arm of the c-phase is connected with the tail of the PWM pulse signal of the upper bridge arm of the b-phase, and b The head of the PWM pulse signal of the lower bridge arm of the phase is connected with the tail of the PWM pulse signal of the lower bridge arm of the a phase, and the head of the PWM pulse signal of the lower bridge arm of the c phase is connected with the tail of the PWM pulse signal of the lower bridge arm of the b phase. By adopting the zero-common-mode modulation algorithm of the present invention, the pulse position of the inverter is controlled in real time. Compared with the traditional modulation algorithm, the instantaneous common-mode voltage is always zero, which can effectively reduce system leakage current and common-mode noise.

Description

technical field [0001] The invention belongs to the field of power electronics, and more particularly, relates to a zero-common-mode modulation method suitable for a modular multilevel converter (modular multilevel converter, MMC). [0002] technical background [0003] Modular multilevel inverter MMC, as a promising power electronic interface, has been applied in medium voltage, high voltage and other fields, and has many advantages, such as: low switching frequency, low harmonic distortion and low electromagnetic interference, etc. Modular multilevel modulation algorithms are mainly divided into two types: (1) low switching frequency algorithms, such as: nearest level approximation, selective harmonic cancellation algorithms; (2) high switching frequency algorithms, such as carrier phase shift modulation, Carrier layer modulation. [0004] In the previous modular multilevel modulation algorithms, the research on common mode voltage is less. However, there are high-freque...

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Problems solved by technology

[0005] Aiming at the improvement needs of the prior art, the present invention provides a zero-common-mode modulation method suitable for modular multilevel inverters, which aims to solve the problems of high-frequency common-mode voltage and common-mode voltage in the existing MMC system. Leakage current and common mode interference can be generated through stray capacitance, which can endanger the technical problems of motor bearings and photovoltaic systems

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