A Multilevel Converter with Common DC Side Capacitors

Abstract

The invention relates to a novel multilevel converter with a common direct current side capacitor. When 2k+j (k is a positive integer, j is equal to 1 or 2) level is output, the common direct currentside capacitor is formed by connecting (2k+j-1) voltage equalization capacitors in series; any bridge arm is formed by connecting 2(2k+j-1) switches composed of a controllable power device with an anti-parallel diode; 2k layers are provided in nodes between the voltage equalization capacitors; k forward and reverse switch branch circuits are respectively extracted from two ends to the middle part;the other ends of the branch circuits are connected to corresponding layers, from two ends to the middle part, of the node between the bridge arms, wherein the ith branch circuit is formed by connecting i switches in series (i= 1,2...k). When j is equal to 1, the k forward and reverse switch branch circuits have a common connection point, and the switches can only retain the anti-parallel diodes;or the two branch circuits are connected in series, the two ends are respectively connected to a middle point of the common direct current side capacitor and the bridge arms. According to the novel multilevel converter with the common direct current side capacitor, the number of devices used in the multilevel converter is decreased and the size and complexity of the system are reduced. In a multi-phase equilibrium system, the capacitance required by the multilevel converter is significantly reduced.

Description

technical field [0001] The invention relates to a multi-level converter topology with common DC side capacitors, belonging to the technical field of power electronic converters. Background technique [0002] Limited by the withstand voltage level of existing controllable power devices, traditional two-level converters need to use switches in series in applications of medium and high voltage levels, which has the problem of dynamic and static voltage equalization of switches, and its output The waveform distortion rate is high, and a larger volume filter is required. [0003] Compared with the two-level converter, the multi-level converter can reduce the harmonic content of the output waveform while achieving a higher level of output voltage, and effectively reduce the volume and insulation level of the filter, which is very suitable for high-voltage and high-power occasions . [0004] However, in the existing multi-level topology, the number of clamping devices in the diod...

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Problems solved by technology

[0004] However, in the existing multi-level topology, the number of clamping devices in the diode-clamped and capacitor-clamped topologies will increase sharply as the number of levels increases, resulting in complex structures and reduced reliability; the cascaded H-bridge topology It needs to be powered by a large number of independent power sources, which increases the size of the device in disguise; the modular multi-level topology uses a large number of switches and floating capacitors, and its control complexity and cost are relatively high

These shortcomings have limited the popularization and application of current multilevel converters.

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