M3C pre-charging method based on staggered grouping

Abstract

The invention discloses an M3C pre-charging method based on staggered grouping. According to the invention, on the premise that the capacitor voltage of an M3C system is charged, the pre-charging timeis shortened as much as possible and the control is simple, the pre-charging voltage can still reach a required set value when the input side (charging power supply) is relatively low and the numberof sub-module capacitors is relatively large and the voltage is relatively high, and meanwhile, the sub-module capacitor voltage is balanced. On the basis of the analysis, a grouping method is reformulated instead of simply dividing into two types, and an interleaved charging method is used at the same time, so that the charging time difference is reduced as much as possible, and the capacitor voltage is prevented from changing greatly after the charging is completed.

Description

technical field [0001] The invention relates to a sub-module capacitor precharging method of a modular multilevel matrix converter, and the specific method is suitable for any M3C topology converter. Background technique [0002] Modular multilevel matrix converter (M3C for short) is a new type of AC-AC power conversion device, which can realize arbitrary conversion of different amplitudes, frequencies, and power factors at the input and output terminals. The advantages of both matrix converter (MC) and modular multilevel converter (MMC) have great advantages in high-voltage and large-capacity power electronic conversion. In addition, M3C can also realize bidirectional conversion of power. Therefore, the M3C system has great prospects in future research and application. like figure 1 The topological structure of the M3C converter and its sub-modules is shown: the 3×3 M3C topology has 9 bridge arms, and each bridge arm is composed of a bridge arm inductor L and several ful...

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Problems solved by technology

However, this method has two serious disadvantages: 1) When the voltage on the input side (charging power supply) is low and the voltage on the output side is high, when the number of sub-modules is large and the capacitor voltage is high, this method only Capacitor voltage of the sub-module can be charged to a relatively low value, but often cannot reach the predetermined value, so this method will not be applicable in this case (for example, the voltage on the input side is 300V, the capacitor voltage of the sub-module is 250V, and the number of sub-modules is 2 and above); 2) Due to factors such as capacitor internal resistance loss, line loop loss, and power supply to the sub-module control power supply, the capacitor voltage of the first-charged sub-module will drop, making the two groups of capacitor voltages before and after There is a deviation, which will cause the energy imbalance of the bridge arm in severe cases, and will cause a large inrush current when the system enters the normal working time

Therefore, in actual use, this method has a large limitation

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