## 5 Structural Hybrid of Reviewed Converters
### Bidirectional Resonant Converters  
These converters are normally used as a linkage between the energy storage components and the grid utilities or \(DC\) bus [132]; they can also be used in \(EVs\), microgrids, and vehicle-to-grid (\(V2G\)). \(BDCs\) are normally connected with energy storage components such as supercapacitors or batteries, with a wide range of voltage variation during operation. Hence, \(BDCs\) are not considered efficient over a wide range of voltages [133; 134]. More attention has been given to the dual active bridge (\(DAB\)) converter because of its simple nature, high efficiency, safety, and wide range of soft-switching capability [135]. \(BDCs\) can also be achieved with a current-fed inverter on the transformer side with low voltage and with a voltage-fed inverter on the side of the transformer with high voltage. However, conventional converters are associated with certain issues, such as switching losses and not being able to achieve soft switching under wide load changes. Hence, the proposed resonant-based bidirectional \(DC\)-\(DC\) converter was suggested to address these issues of conventional converters [136; 137]. Various studies have focused on the alteration of _resonant network_ structures to improve the performance of resonant-type \(IBDCs\). Most of the studies have concentrated on \(CLLC\)- and \(CLLC\)-type resonant \(IBDCs\) because of their symmetrical attributes in both power flow directions. The study by [134] proposed bidirectional designs of \(CLLC\) and \(CLLC\) resonant converters that will ensure high-efficiency operation over a wide gain range. The attributes of \(LLC\) resonant converters include low cost, high power, and better efficiency, and these made it suitable for industrial application [138]. The most popular bidirectional isolated converters in the industries are series resonant converters (\(SRCs\)) because they can realize open-loop bidirectional power flow operation. \(LLC\) resonant tanks are considered better options for improving the regulation of output voltage under bidirectional operation because their usage in bidirectional converters demands two different modes of operation based on the power flow direction [139]. The study by [140] presented a light electric vehicle fast charger with a lithium-ion battery and supercapacitor, together with an \(AC\)/\(DC\) rectifier, full-bridge \(LLC\) resonant converter, as shown in Figure 34, and light electric vehicle (\(LEV\)) battery. The research suggested a fast-charging system using a soft-switched \(LLC\) resonant converter in the \(ZVS\) area. Compared to the past, the regular use of lead-acid batteries has been reduced due to emissions into  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**No** & **Topology** & **Diode Clamped** & **Flying Capacitor** & **Cascaded HB** \\ \hline
1 & Semiconductor power switches & \(2\times(m-1)\) & \(2\times(m-1)\) & \(2\times(m-1)\) \\
2 & DC bus capacitors & \((m-1)\) & \((m-1)\) & \(\frac{(m-1)}{2}\) \\
3 & Balancing capacitor per phase & 0 & \(\frac{(m-1)(m-2)}{2}\) & 0 \\
4 & Clamping diodes per phase & \((m-1)(m-2)\) & 0 & 0 \\
5 & Unbalancing voltage & Average & Great & Tiny \\  & & Renewable energy, motor & Renewable energy, motor & Renewable energy \\  & & drive system, static & drive system, static & battery system, motor \\
6 & Application & synchronous & synchronous & drive system, power \\  & & compensator & & factor compensators, \\  & & (_STATCOM_), & & electric vehicle drives. \\ \hline \hline \end{tabular}
\end{table}
Table 3: Comparison of multilevel inverters based on the number of components utilized.  
the air and environment; therefore, new \(LEV\) systems with fast charging mechanisms have been proposed by using a lithium-ion battery of 800 Watt-hour and a supercapacitor of 50 Wh.