On-line reliability monitoring system of NPC type three-level inverter and method thereof

Abstract

The invention discloses an on-line reliability monitoring system of an NPC type three-level inverter and a method thereof. The method comprises: switching states of twelve power switching devices in a three-phase bridge arm are determined based on a current flowing path of an NPC inverter, micro adjustment of PWM waveforms within each period is carried out to select a proper measurement time period, and detection work is carried out on a normal working condition; an external auxiliary power supply unit injects currents with two kinds of amplitudes into a measured device within the detection period, and a data acquisition unit measures on-state voltage drops of the IGBT power devices and diodes connected with the devices in an anti-parallel mode; and an analysis reliability unit generates a breakover drop and junction temperature relation graph as a calibration curve by using measured voltages as temperature-sensitive parameters, and a reference look-up table is obtained based on the obtained junction temperatures and on-state voltage drops. When amplifications of breakover drops of the devices are monitored to exceed a threshold value under high currents in an on-line mode, occurrence of bonding wire failure phenomena inside the IGBT devices can be determined. And healthy states of all devices are obtained successively to obtain a reliability detection result of the inverter.

Description

technical field [0001] The invention belongs to the field of online health monitoring of power devices, in particular to a reliability monitoring system and method for three-level NPC inverter topology. Background technique [0002] Compared with the traditional two-level inverter, the multi-level inverter has the advantages of increasing the number of output levels, better harmonic spectrum, and less voltage stress on the device, but because the multi-level circuit uses a large number of More switching devices lead to a corresponding reduction in the reliability of the circuit, and any device failure may cause the entire circuit to stop working, and even affect the safety of other circuits, resulting in immeasurable economic losses. [0003] Device junction temperature is one of the main factors to measure the thermal reliability of IGBT power devices. At present, there are few studies on the mechanism of performance degradation and reliability decline of power devices und...

AI Technical Summary

Problems solved by technology

However, this method can only quickly identify the main circuit voltage change after the device fails, and cannot realize the diagnosis and prediction before the device fails.

[0006] In the existing patents, the use of contact or non-contact direct measurement methods for measuring junction temperature cannot achieve online real-time monitoring of the inverter operating state

Images