# State-of-the-Art DC-DC Converters for Satellite Applications: A Comprehensive Review
## 3 Review of DC-DC Converters for Satellites
### Isolated Topologies
#### 3.2.6 Dual-Active Bridge Converter  
The Dual-Active Bridge (DAB) topology has been widely accepted among researchers over the past couple of years for high-power density applications. It exhibits high performance and efficiency with inherent galvanic isolation and soft-switching capabilities. It is well-suited for handling high power and has a simple structure and high transformer utilization factor [95; 101]. In a study by NASA [102], a bidirectional interleaved DAB converter was studied for satellite EPSs. A prototype of the converter (2 kW per module) using 650 V GaN semiconductors was developed and tested under cryogenic conditions. The study demonstrated the benefits of using the DAB converter for satellite EPSs. Several works have been proposed in the literature based on DAB converters for high-power applications in electric aircraft. As the study in [102] opened new possibilities for DAB converters for satellite applications and because the design limitations for electric aircraft and satellites are comparable (although not the same), these topologies are discussed in this review.  
Ref. [103] performed the modeling, design, implementation, and performance evaluation of the DAB converter using SiC switches for aircraft electrical power networks. Ref. [104] compared the conventional DAB, Active Neutral Point Clamped (ANPC), Neutral Point Clamped (NPC), and Input-Series Output-Parallel (ISOP) converters using Wide-Band-Gap (WBG) devices for more electrical aircraft (MEA) applications.  
Figure 14: (a) Current-fed cascaded buck and full-bridge converter. (b) Resonant LLC converter.  
Figure 15a-e show these DAB topologies. A comparison in terms of efficiency, heat management, power density, specific power, and EMC is shown in Figure 15f[104]. The figure illustrates the superiority of the ANPC type concerning efficiency, heat regulation, and power density. The ISOP and conventional DAB converters exhibit comparable results, with the conventional DAB showing higher efficiency. Although the NPC converter provides the best EMC performance along with the ANPC type, it shows poor performance in terms of the other three parameters. The design of a conventional DAB converter for space applications was discussed in [105].  
Regarding the modulation strategy, single-phase-shift modulation is the most widely used method in DAB converters due to its simplicity [106; 107]. Advanced modulation methods, like extended or dual-phase-shift modulation and triangular or trapezoidal current modulation, were proposed in [67; 108]. [PERSON]. [109] proposed an interleaved parallel DAB topology with a coupled inductor for MEA and compared the converter's performance with three modulation methods viz. single-phase shift, extended phase shift, and PWM plus single-phase shift. The topology is shown in Figure 15e. According to the study, single-phase shift combined with PWM can handle at least twice the power of a conventional DAB converter, while an extended phase shift can lower the current stress.  
Figure 15: DAB converter topologies: (**a**) conventional, (**b**) ISOP type, (**c**) NPC type, (**d**) ANPC type, (**e**) parallel interleaved type. (**f**) Comparison of power density, thermal management, volume, efficiency, and EMI of various DAB converters.