# Solid-State Transformer-Based DC Power Distribution Network for Shipboard Applications
## 4 Simulation Results
### Full Load Operation of the Shipboard Electric Power System  
Scenario 1 involves simulating the whole shipboard system at the rated conditions of each component and delivering the full load power from the generator, \(P_{G}\), 2 MW, to the propulsion motor, \(P_{Motor}\), 1.5 MW, and the LVDC side loads, \(P_{Load}\), 0.5 MW. The control techniques discussed previously for each stage converter are applied, where the GS-VSR regulates the HVDC bus voltage, \(V_{HVDC}\), at 10 kV and ensures the unity power factor operation of the generators (\(Q_{g}\) = 0). Besides, the DAB converter keeps the LVDC bus voltage, \(V_{LVDC}\), regulated at 650 V and provides bidirectional power flow operation. The propulsion motor drive system controls the motor speed to be constant at the rated speed, \(N\), of 1500 rpm. The PV and the storage system are operated to feed part of the LVDC side loads, \(P_{BB}\), 0.1 MW, and the DAB converter supplies the rest of the power, \(P_{DAB}\), 0.4 MW.  
The generator plots are shown in Figure 8, namely the generator currents, voltage, active, and reactive powers. It is clear that the GS-VSR successfully controls the generator current at the unity power factor with an acceptable high quality current waveform, as shown in Figure 8a. This conclusion is further proved as the generator's active power, \(P_{G}\), supplies the whole system, while the reactive power, \(Q_{G}\), is nullified, as depicted in Figure 8b. Moreover, the HVDC side operation is presented in Figure 9, highlighting the HVDC bus voltage and powers. It is shown that the well-designed control technique at the GS-VSR can regulate the HVDC bus voltage, \(V_{HVDC}\), at 10 kV.  
Figure 8: Simulation results of the main generator. It is clear that the GS-VSR successfully controls the generator current at the unity power factor with an acceptable high quality current waveform, as shown in (**a**). This conclusion is further proved as the generator’s active power, \(P_{G}\), supplies the whole system, while the reactive power, \(Q_{G}\), is nullified, as depicted in (**b**).  
In addition, the GS-VSR can supply the DAB and six-phase motor with around 2 MW, which is divided among the motor demand and the LVDC side demand that is delivered by the DAB converter.  
Similarly, the LVDC operation, namely LVDC voltage and powers, is highlighted in Figure 10. Accordingly, the DAB converter can efficiently regulate the LVDC bus voltage, \(V_{LVDC}\), at 650 V regardless of its loading condition. Meanwhile, the LVDC side powers, i.e., VSI input power, \(P_{VSI}\), DAB output power, \(P_{DAB}\), PV power, \(P_{PV}\), and the ESS power, \(P_{ESS}\), are filtered and contain lower harmonic content. For instance, The LS-VSI consumes around 0.5 MW, which is supplied by the DAB and the PV-battery system with 0.4 MW and 0.1 MW power shares, respectively.  
For the six-phase motor, the simulation results are shown in Figure 11. The employed machine is an asymmetrical six-phase with a spatial phase shift of 30\({}^{\lx@math@degree}\) between the two three-phase winding sets. The motor speed is regulated to follow the reference speed,  
Figure 10: LVDC side operation waveforms.  
Figure 9: HVDC side operation waveforms.  
which is set to 1500 rpm. For prolusion motor applications, the load torque is proportional to the speed square. Hence, the motor developed torque rises as the motor speed increases.