Double-load three-phase nine-switch group mmc inverter and its control method

Abstract

The invention provides a double-output three-phase nine-switch-block MMC inverter and a control method thereof. The inverter comprises a direct-current power supply, a first bridge arm, a second bridge arm, a third bridge arm, a first three-phase load and a second three-phase load. Each of the first bridge arm, the second bridge arm and the third bridge arm is formed by connecting an upper switch group, a middle switch group, a lower switch group and coupling inductors in series. The three ends of the first three-phase load are connected with the upper ends of the middle switch blocks of the first bridge arm, the second bridge arm and the third bridge arm respectively. The three ends of the second three-phase load are connected with the lower ends of the middle switch blocks of the first bridge arm, the second bridge arm and the third bridge arm respectively. The inverter is controlled by carrier phase-shifting PWM and has two circuits of three-phase alternating-current output of the level with the voltage of 2N+1, the voltage stress borne by each switching tube in each power switch unit is only 1 / N of the voltage of the direct-current power supply, and the inverter is suitable for high-voltage, large-power, three-phase alternating-current and double-load occasions. Each pair of coupling inductors in the inverter can be replaced by two independent inductors.

Description

technical field [0001] The invention relates to the field of module combination multilevel (MMC) converters, in particular to a dual-output three-phase nine-switch group MMC inverter and a control method thereof. Background technique [0002] At present, power converters are developing in the direction of miniaturization, high reliability and low loss. Under this trend, there are two directions for improving the converter: reducing passive components or improving the topology of the converter to reduce active components. New progress in the direction of source devices. Compared with the traditional twelve-switch converter, the three-phase nine-switch converter reduces three switches and the corresponding drive circuit, and has certain advantages in applications considering cost and volume. However, the two single-phase outputs of the nine-switch converter are both two-level, and the output AC waveform is relatively poor. In addition, the voltage stress of each of the nine ...

AI Technical Summary

Problems solved by technology

However, when two AC lines with different frequencies are connected, two MMC converters are required, which greatly increases the engineering cost

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