Open-circuit fault diagnosis in 3-phase uncontrolled rectifiers

This paper proposes a detection method for open-circuit faults in a 3-phase uncontrolled rectifier that forms the input stage of a single-phase current controlled power converter. The rectifier is driven by a 3-phase wind generator with variable amplitude and frequency. The algorithm is based on fault signatures embedded within the output voltage ripple of the rectifier. It is demonstrated that seven different classes of open circuit faults can be detected and isolated.

I. Introduction

A significant proportion of faults in power converters are caused by failures of power semiconductor devices. Such faults may be classified into open circuit and short circuits faults. Short circuit faults are typically caused by excessive voltage or current. Open circuit faults may be caused by breaking of bond wires due to thermal cycling, short circuit induced rupture, or driver failure in the case of rectifiers implemented using IGBT's. Fuses, breakers, overload relays, and electronic overcurrent protection circuits provide protection when short circuit faults occur and the normal reaction is to shutdown the entire system. Open circuit faults are more challenging to detect because these are not normally recognized by the protection logic so the system will usually continue to operate after a failure occurs but with degraded performance [1]. The degraded performance is not without cost; it usually places increased stress on other system components leading, in time, to further failure [2].