Device open-circuit fault diagnosis circuit for diode neutral point clamped (NPC) three-level inverter

Abstract

The invention discloses a device open-circuit fault diagnosis circuit for a diode NPC three-level inverter. The circuit comprises three open-circuit fault diagnosis unit circuits with same structures. The open-circuit fault diagnosis unit circuits are composed of signal sampling units, signal adjusting units, narrow pulse filtering units, first and second pulse missing detection units and upper and lower bridge arm circuit determining units. The signal sampling units isolate and sample bridge arm voltages, the signal adjusting units perform rectification, voltage separation and filtering on voltage signals after isolation and sampling, the narrow pulse filtering units and the first and second pulse missing detection units determine whether open-circuit faults occur to devices in bridge arm circuits, and the upper and lower bridge arm circuit determining units distinguish that fault devices are devices in an upper bridge arm circuit or a lower bridge arm circuit. By means of the device open-circuit fault diagnosis circuit for the diode NPC three-level inverter, which device in the three-level inverter is subjected to open-circuit fault can be detected accurately, the diagnosis speed is fast, and the diagnosis accuracy is high.

Description

technical field [0001] The invention relates to an inverter fault detection technology, in particular to a device open-circuit fault diagnosis circuit for a diode mid-point clamped three-level inverter. Background technique [0002] The multi-level converter is a new type of converter that realizes high-voltage and high-power output by changing the topology of the converter itself, and it does not need a buck-boost circuit and a voltage-balancing circuit. The most typical multilevel converter is the diode neutral point clamped (Neutral Point Clamped, NPC) three-level inverter, the main circuit of which is as follows figure 1 shown. Compared with the traditional two-level inverter, the diode NPC three-level inverter has a better harmonic spectrum due to the increase in the number of output voltage levels, and the voltage stress on each switching device is smaller. Therefore, the diode NPC three-level inverter has been widely used in practice, such as the frequency converter...

AI Technical Summary

Problems solved by technology

This solution has the advantages of fast diagnosis and high reliability, but the diagnosis result does not accurately locate a certain switching device, and it needs to be searched manually, and the judgment of whether the PWM voltage waveform is abnormal is all through human eyes on the oscilloscope. It is obtained by observing the displayed waveform on the screen, which greatly affects the accuracy of the diagnostic results.

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