# Solid-State Transformer-Based DC Power Distribution Network for Shipboard Applications
## 4 Simulation Results
### PV-Battery Power Management Algorithm  
In scenario 3, the simulation results of the power management algorithm, which is utilized to control the PV-battery system during different irradiance and SoC conditions, are given in this subsection. Besides, the corresponding effect on the power delivered from the DAB converter to the LVDC side, \(P_{DAB}\), and LVDC side loads, \(P_{Load}\), is considered. The system is simulated over a 24-h domain. The LVDC side loads are assumed to consume the full power of 500 kW.  
In addition to the efficient shipboard DC network control, a power management strategy is developed to optimally dispatch the power at the LVDC side on a daily basis, as depicted in Figure 13. It is assumed that the load demand, \(P_{Load}\), at the LVDC bus side is constant during the day, with a value of 500 kW. Initially, the \(SoC\) of the batteries is assumed to be 90%. Besides, the limited power from the PV-battery system, \(P_{Lim}\), is defined to be 100 kW. The simulation scenario can be divided as follows:  
1. Stage 1 (0-5 h): In this stage, the generated power from the PV system, \(P_{PV}\), is zero. Due to the limited PV-battery power and the initial \(SoC\), the battery system power, \(P_{ESS}\), supports the load demand with 100 kW, which yields considerable reduction in the battery \(SoC\), reaching 30% at 5 h. Meanwhile, the rest of the demand is supplied from the DAB power, \(P_{DAB}\), with 400 kW.
2. Stage 2 (5-11.5 h): At 5 h, the controller disconnects the battery system since the SoC drops to the minimum level. Thus, the load demand is initially supplied from the DAB converter (\(P_{DAB}=500\ kW\)) only. Then, the PV system starts to share the load power, \(P_{Load}\), with the DAB converter till the end of this interval. As a result, the DAB power, \(P_{DAB}\), share drops to 400 kW.
3. Stage 3 (11.5-18 h): At the beginning of this interval, the PV power, \(P_{PV}\), becomes higher than the PV-battery power limit, \(P_{Lim}\). Thus, the battery charging process is resumed and the power difference between the PV power, \(P_{PV}\), and the limit power, \(P_{Lim}\), is fed back to the ESS. This, therefore, justifies the negative value of the ESS  
Figure 12: Transient effect of the propulsion motor speed change on the SST dynamics.  
power, \(P_{ESS}\). During this period, the DAB supplies 400 kW to the load, whereas the PV-battery system shares the remaining load demand. In addition, the battery \(SoC\) rises to 45% at the end of the period.
4. Stage 4 (18-21.5 h): At 18 h, the battery \(SoC\) becomes higher than 30%, and the PV power, \(P_{PV}\), drops below the limit power, \(P_{Lim}\). Thus, the battery is discharging to maintain the average power supplied by the PV-battery system, \(P_{BB}\), 100 kW. Moreover, the DAB delivers the remaining power of 400 kW to meet the load demand.
5. Stage 5 (21.5-24 h): The battery is disconnected since its \(SoC\) decreases below 30%, and the DAB shares power with the PV to supply the load demand. In that case, the DAB power increases from 470 kW at 21.5 h and ends with 500 kW at 24 h.