I. Introduction
In any modern variable speed drive (VSD) consists of the following integral components, a power electronic converter, a micro-controller, a sensing device, and a motor drive. Failure of any component will impact the operational performance of the machine. Fault diagnosis and fault tolerance operation on power converters are essential for industrial applications such as electric vehicles, aviation, railroad locomotives and generation units [1]. Power electronics systems have emerged as critical components in those application domains. Any power electronics-based drive system must operate reliably for the duration of its design life [2]. The 3-phase 2L-VSI are extensively used in low voltage variable speed drives in comparison with other converter configurations. As per previous statistical studies, 63% of all customers encountered motor failures are from the initial one-year operation of variable speed drive faults [3]. In which 70% of these faults are related to power electronic converters [4]. Among that the power switching device failures render 34% of overall power converter faults [5]. As a result, power converter system failure diagnostics is currently a popular research topic. Even though IGBT is reliable, they are prone to failure due to large temperature variations during variable frequency operation. There are numerous methods proposed in the literature to improve the availability of power devices. In [6], introduces a scheme to minimize the switching frequency, but reduced switching frequency on the other hand can trigger harmonics and rotational pulsation. When selecting a switching control strategy, the tradeoff between PWM harmonics and semiconductor junction temperature must be considered [7]. In this way, the life of the power devices can be improved without losing the inverter performance.