# Solid-State Transformer-Based DC Power Distribution Network for Shipboard Applications
## 5 Experimental Investigation  
This section presents the experimental evaluation of the proposed SST-based shipboard electric power system using a low-scale prototype system rated at 2 kW and a 500 V/250 V DC/DC voltage ratio. The SST, which includes the GS-VSR, DAB, and LS-VSI, is connected to an A6P propulsion motor, and a PV emulator is integrated to the SST LV side. Experiments have been conducted to show the effect of motor dynamics as well as the step loading at the LVDC side on the system performance. The experimental test-bench is depicted in Figure 14, and its parameters are given in Table 4.  
The voltage source converter utilized in this hardware is an NPC-VSC. It offers bidirectional power transfer. In addition, the NPC-VSC is tied to the DAB HVDC bus. The SST uses SiC switches (SiC IGBT LSIC1 MO120E0080) and utilizes 3 fans with 14000 RPM speed to cool up the heat sinks and the HFT. A 50 Hz three-phase supply is used to emulate the  
Figure 13: Power management simulation results.  
generator. The asymmetrical six-phase propulsion motor can be connected to the same HVDC bus without affecting the SST-based LVDC distribution system.  
The 6-phase motor drive system, namely the motor and inverter, is built by rewinding a standard three-phase induction motor with two three-phase winding sets, where the spatial phase shift between the two three-phase winding sets is \(30^{\lx@math@degree}\). The motor is mechanically loaded using a coupled DC-generator having the same power rating. The DSP controller board employed in this drive is the TMS320F28379D Launchpad. Finally, the PV system operates using MPPT algorithm applied on boost converter, which have been tested using a Keysight E4360A modular solar array simulator.  
The generator line currents are shown in Figure 15, where balanced currents are obtained. Moreover, the generator phase voltage and current are in-phase, which ensures unity power factor operation at the generator AC side. Moreover, the GS-VSR can successfully maintain the input DC voltage of the DAB during the full load operation, as shown in Figure 16. Meanwhile, the output DC voltage of the DAB is well regulated at the desired reference throughout the system operation, which, therefore, proves that the DAB is properly functioning. It is worth mentioning that the DAB is controlled based on SPS modulation technique with a feedback PI control. The effect of full-load step-loading at the secondary side is shown at 10 s.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Parameter** & **Value** & **Category** & **Parameter** & **Value** \\ \hline \multirow{3}{*}{**GS-VSR**} & Rated power & 2 kW & & Rated power & 1 kW \\ \cline{2-5}  & Phase voltage & 110 V (rms) & \multirow{3}{*}{**Propulsion**} & Voltage & 150 V (peak) \\ \cline{2-5}  & Frequency & 50 Hz & & Phase current & 2.8 A (rms) \\ \hline \multirow{3}{*}{**DAB**} & Rated power & 1 kW & & Rated frequency & 50 Hz \\ \cline{2-5}  & Voltage ratio & & & Power & 100 W \\ \cline{1-1} \cline{2-5}  & (prim/sec) & & \multirow{3}{*}{**PV**} & Output voltage & 250 V \\ \cline{1-1} \cline{2-5}  & Current ratio & & & & \\ (prim/sec) & & & & & \\ \cline{1-1} \cline{2-5}  & & & & & \\ \end{tabular}
\end{table}
Table 4: Test-bench parameters.  
Figure 14: Experimental test-bench.  
Figure 17 shows the six-phase motor dynamic performance. In the asymmetrical configuration, the spatial phase shift between the two three-phase winding groups is \(30^{0}\)  
Figure 16: DAB experimental readings.  
Figure 15: GS-VSR voltage and current waveforms.