Introduction
DC-link capacitor, also known as an intermediate circuit capacitor is one of the most crucial power conversion stages for several industrial applications such as adjustable speed motor drives, wind power systems, photovoltaic systems, and electric vehicles [1], [2]. The main functions of DC-link capacitors are to compensate the instantaneous power difference between the source (usually a rectifier bridge) and output load (usually an inverter whose mean value is constant in steady-state operation), absorb the high-frequency currents generated by inverter modulation technique, thereby preventing the flow of switching frequency current harmonics into the source and to smoothen voltage ripple superimposed on the DC-link voltage [3], [4]. Aluminum electrolytic capacitors (El-caps) are one of the most commonly used DC-link capacitors, due to their advantage of providing a high capacitance per unit volume at low costs compared to other types of capacitors. However, recent studies show that capacitors, in general, contribute to 30% of the total failure root causes in the power electronic systems [5] and they are considered as the most fragile components in a power electronic system [3]–[6].