Study on diagnostics and tolerant operation of open-circuit fault in three-phase PWM converters

Abstract

The three-phase pulse width modulated (PWM) converters are widely used in motor drive and power quality applications such as powered wheelchairs, aerospace, medical and military applications, nuclear power plants, uninterruptible power system, active power filters, and more recently, in renewable energy systems and electric/hybrid vehicles. In these applications, because an accident or fault can result in huge damages to the human life and environments, the reliability is one of the most important factors to guarantee the safe, continuous and high performance operation under even some accidents or faults. Generally, when an accident or fault occurs, the system has to be stopped for emergency or non-programmed maintenance schedule. Due to the high cost of unexpected maintenance, the development of a reliable system is an area of great interest during the last years.Some statistical studies show that about 38% of the failures are found in power converters and the most of faults are occurred to the power switches. More recently, an industry-based survey considering the reliability in power converters also shows that power switches, capacitors, and gate control circuits are the most susceptible components. Another study shows that semiconductor, soldering, and printed circuit board (PCB) failures in device modules have total 60% of the system failures. Most of power converters use insulated gate bipolar transistors (IGBTs) as power switches because of their high voltage and current ratings and ability to handle short-circuit currents for periods exceeding 10us. In general, IGBT failures can be broadly categorized as short-circuit faults and open-circuit faults. The short-circuit fault may happen due to an improper gate signal so that both power switches in a leg of the converter are turned on. This results in a short circuit of the capacitor in the DC-link that blows out the other compo-nents particularly switching devices. Therefore, the short-circuit fault is on...