## 2 Bidirectional DC-DC Converters
### Classification of Bidirectional DC-DC Converter
#### 2.1.2 Isolated Bidirectional \(DC\)-\(DC\) Converters (IBDCs)  
There are no secure galvanic isolation standards in the non-isolation \(BD\) converter; hence, most applications use _IBDCs_ rather than _NIBDCs_. _IBDCs_ rely on a great frequency transformer to offer galvanic isolation. In numerous applications and with regard to overburden for the safety of the source, galvanic isolation is vital, in addition, to reduce commotion and voltage coordination between conditions [55]. Most _IBDCs_ have similar structures, as shown in Figure 10. This converter works in two stages: great frequency switching by the \(DC\)-\(AC\) converter and the utilization of a high-frequency transformer to maintain the galvanic isolation between two sources, as well as the utilization of transformers to coordinate the voltage between various stages for the best possible plan and enhancement of various stages [31, 56]. Isolated bidirectional \(DC\)-\(DC\) converters with a basic structure were proposed by [31] to function as a flexible interface for power processing between the energy storage system and the other system components. The _IBDC_ has some benefits, such as having no need for active or passive elements in soft switching. Secondly, the structure of the transformer is simple; therefore, maintenance and designing tasks are also simple. Additionally, both parts face the same issue of stresses in the switch currents. This approach also relies on the average current control method or peak current mode control. The absence of extra inactive components ensures quicker dynamic conduct. On the other hand, this converter has drawbacks, such as losing soft switching in light load conditions, and this control is sensitive to a slight variety of flux, particularly when bus voltages are high. An additional weakness is that currents flowing in \(DC\) buses hold great ripple content; this demands fitting filtering circuits, which makes the circuit complex [56, 57]. An isolated converter has many topologies, such as the push-pull _IBDC_, forward _IBDC_, fly-back _IBDC_, dual half-bridge _IBDC_, _Cuk IBDC_, and dual active full-bridge _IBDC_[58, 59, 60, 61]. The efficiencies of the full-bridge and half-bridge topologies endear them to many applications [62, 63]. Dual Half-Bridge (DHB) IBDC  
One of the most commonly used isolated bidirectional \(DC\)-\(DC\) converters is the dual half-bridge (_DHB_) converter (see Figure 11) [18, 64]. Isolated \(DHB\) bidirectional \(DC\)-\(DC\) converters have great power density, soft switching, and simplicity in control; thus, they are suitable for \(EV\) application. They have an approximate efficiency of 92 to 94%; they have two sides--a low and a high voltage side--where voltage is fed to the half-bridge converter on the right side (\(A\) side) and modified current feeds the half-bridge on the low  
Figure 10: Structure of _IBDC_ (BASIC) [31]. Figure 9: Two-phase interleaved half-bridge bidirectional \(DC\)/\(DC\) converter [54]. voltage side. They are also called boost half-bridge (_B_ side) and are usually on the lower side since they consist of a capacitor or battery _DC_ energy source in which a low current ripple is preferred [65]. Additionally, the battery sector of the circuit contains an inductor \(L_{\text{dc}}\) and two half-bridges, each on either side of the main transformer. For each switching device, there is a small parallel capacitor that enables soft switching. The boost style working mode of the circuit is established when there is power flow from the low to high voltage side (_HVS_); this maintains the _HVS_ voltage at the expected high level. Contrarily, the circuit works in the buck mode when recharging the battery from any _RES_. The _HVS_ switch is performed with _IGBTs_ while the low voltage side (_LVS_) switch is performed with _MOSFETs_.