The third classification of _DC-DC_ converter is soft switching, also known as resonant converters; these were developed to overcome the issues in hard switching as revealed by several researches, especially related to their industrial applications [14; 15]. Soft switching can either be zero current switching (_ZCS_) or zero voltage switching (_ZVS_). Compared to liner regulators, these two have better efficiency and ability to work at high switching frequencies, which permit the use of a  
Figure 1: Application of power electronic converters in a renewable energy system. small ferrite transformer core; they can also work in a wider range of _DC_ input voltages compared to linear regulators. Bidirectional _DC-DC_ converters are receiving much attention for both academic and industrial applications; they are mainly used to maintain the reliability of systems and as an interface between the battery and supercapacitors as storage devices [17]. Bidirectional _DC-DC_ power converters are increasingly being used in a variety of applications that demand power flow in both directions. These include, but are not limited to, energy storage systems, uninterruptable power supplies, electric vehicles, and renewable energy systems, to name a few. The classification and different types of bidirectional converters are presented in detail in the following section [18]. Currently, resonant _DC-DC_ converters are the preferred option of power conversion for many low- and high-voltage applications. Resonant _DC-DC_ converters typically contain characteristics that reduce switching losses at the inverter switches and output rectifier diodes, allowing them to operate at higher switching frequencies and yield higher efficiency, resulting in smaller converters. Resonant _DC-DC_ converters come in a variety of topologies, including series resonant _DC-DC_ converters (_SRCs_), parallel resonant _DC-DC_ converters (_PRCs_), and series-parallel resonant _DC-DC_ converters (_SPRCs_) [19]. Due to their simplicity and popularity, many researchers have worked on and recommended resonant converters in various applications [16; 20; 21; 22]. In addition to _DC-DC_ conversion, _DC-AC_ conversion is also required to supply _AC_ loads as well as grid integration of _DERs_. Multilevel inverters are one of the most researched power converter topologies in industrial and residential applications. In recent years, multilevel inverters have received a lot of attention in the applications of medium-voltage and high-power ranges owing to their numerous advantages, and some of the advantages of multilevel inverters over the traditional two-level inverters include lower _EMI_, less harmonic distortion, and lower voltage stress on semiconductor elements. Their drawback is that they require a large number of semiconductor elements. When compared to two-level inverter topologies with the same power ratings, multilevel inverters are more effective in eliminating the harmonic component of voltage and current waveforms. Multilevel topologies are classified into different types, such as cascaded h-bridge, diode-clamped, and capacitor-clamped inverters [23; 24]. In applications requiring high-power converters, multilevel inverters are vital. They are also widely used in clean energy sources where they serve as a connection between renewable energy sources (_RESs_), such as _PV_ modules, and high-power loads [25]. Among the common application areas of multilevel inverters (_MLI_) are Flexible Alternative Current Transmission System (_FACTS_) devices, power converters, and reactive power compensation systems for high-power _AC_ motors [25; 26; 27]. Apart from individual topologies, recently the hybridization of topologies is becoming popular. For an example, resonant converters are enabled to operate in bidirectional mode for power transfer both ways. Bidirectional resonant converters are relatively easy to integrate  
Figure 2: Classification of _DC-DC_ converters [16]. amongst other components [28; 29].