## 1 Introduction  
Reducing greenhouse gas emissions has become a global priority, which has made it imperative to increasingly use clean energy sources, particularly renewable energy sources. Therefore, phasing out oil and its derivatives is now a key objective of greenhouse gas reduction. In the European Union, in 2022, electricity was the second largest energy vector after oil and its derivatives, representing a share of the total final energy consumption of 23% [1]. On the other hand, the International Energy Agency's Electricity 2024 report indicates that the share of electricity in final energy consumption increased from 18% in 2015 to 20% in 2023 [2]. This reflects a broader global shift toward electrification and sustainable energy use. This paradigm shift is impacting all sectors of the economy. For instance, in the primary sector, in agriculture and fishing, there is an increasingly broad integration of hybrid and electric vehicles [3], robots, and drones [4; 5], which increase the operational efficiency and reduce the environmental impact of these sectors. In turn, in the secondary sector, industrial electrification represents an irreversible trend [6] which not only optimizes energy efficiency but also guarantees a substantial reduction in greenhouse gas emissions. Finally, the tertiary sector is also witnessing an unprecedented transformation, which is marked by the increasing use of electric vehicles in public transport systems [7; 8] and the adoption of advanced, energy-efficient electrical equipment in sectors such as healthcare [9] and commerce [10]. Electrification relies on electrical circuits that convert grid-supplied waveforms into forms that are compatible with the specific requirements of each load. In this context, power electronics plays a crucial role by enabling the design of power converters (PCs) that efficiently transfer energy from one form (source) to another (load). Failures in power converters cause significant financial losses resulting from unexpected shutdowns [11]. On the other hand, in critical systems, these failures pose serious risks to human life, notably when they effect medical equipment and transport vehicles, where converters are vital to ensure the reliable operation of essential functions [12]. PCs typically consist of switches, lossless energy storage elements, and magnetic components such as transformers. Among these, capacitors, a key energy storage device, are particularly vulnerable and are responsible for approximately 30% of all PC failures [13]. Capacitor failures typically advance gradually but can lead to catastrophic outcomes if not addressed promptly. As a result, designing real-time fault diagnosis techniques (FDT) to monitor the health status of capacitors has become essential. This topic has gained significant attention in recent years due to increasing electrification, although initial research efforts date back more than two decades ago [14]. FDTs can be classified from both operational and conceptual perspectives. From the operational standpoint, FDTs are typically divided into offline (OFF), quasi-online (QON), and online (ON). Offline fault diagnosis techniques (OFF-FDTs) involve removing the capacitor from its original circuit (the PC) and testing it separately in a dedicated setup. While this approach can yield highly accurate results [15], it is generally impractical because it requires shutting down the PC and physically removing the capacitor from the PC. In quasi-online fault diagnosis techniques (QON-FDTs), the capacitor is not removed from the PC, and its health status is assessed during a routine PC interruption. The routine interruption may represent an atypical converter operation or special operating configuration [16]. Online fault diagnosis techniques (ON-FDTs) can be implemented during normal converter operation; thus, the capacitor's health status can be assessed constantly and uninterruptedly, which ensures that there are no interruptions or the need for the introduction of atypical operating conditions.