Flying capacitor NPC three-level topology

Abstract

The invention provides a flying capacitor NPC three-level topology, comprising: two half-bus capacitors and at least one bridge arm, wherein the bridge arm comprises a flying capacitor, two inner tubeunits, two outer tube units and two clamping diodes; the capacitance value of the flying capacitor is greater than a specific value. Since the flying capacitor has a clamping effect on the two innertube units and has a large capacitance value, the voltage fluctuation cannot cause the overvoltage of a switching tube no matter what kind of short circuit fault occurs, thereby avoiding the overvoltage damage to the switching tube unit and further improving circuit safety.

Description

technical field [0001] The invention belongs to the technical field of circuit short circuit protection, and more specifically relates to a flying capacitor type NPC three-level topology. Background technique [0002] At present, the voltage stress of each switching tube of the three-level topology is only half of the input voltage, and at the same time it can effectively reduce the harmonic content and improve the quality of the output waveform. It is widely used in voltage applications. [0003] The NPC (Neutral Point Clamp, diode-clamped) three-level topology is the most classic and widely used three-level topology. see figure 1 , an NPC three-level bridge arm is composed of four reverse conduction switch tubes and two clamping diodes, the reverse conduction switch tubes S1 and S4 are outer tubes, and the reverse conduction switch tubes S2 and S3 are inner tubes. The reverse conduction switch can be a MOSFET or an IGBT with a reverse diode. Capacitors Cd1 and Cd2 are ...

AI Technical Summary

Problems solved by technology

[0004] However, when a short circuit occurs in the NPC three-level topology, the switching logic during normal operation is destroyed, and the NPC three-level topology has no clamping effect on the inner tube, which may cause overvoltage damage to the inner tube, which in turn will cause the entire bridge arm and even the entire bridge arm to be damaged. circuit damage

The NPC three-level topology cannot effectively protect all short-circuit conditions, and after a short-circuit occurs in the inner tube, it must be delayed for a period of time before it can be turned off, which increases the possibility of damage to the switch tube and makes the circuit less safe.

Images