## 3 Simulation Results  
A novel hybrid test with four buses--an LVDC, HVDC, and LVAC distribution system with a radial-type electrical grid--is presented in Figure 12. It should be highlighted that a protection scheme based on AC and DC circuit breakers (ACCB and DCCB) for the novel hybrid test was proposed to improve the reliability of all the components. In particular, the LVDC and LVAC distribution system comprises a photovoltaic generator, wind turbine, and an ESS based on lithium-ion batteries. More specifically, the LVDC distribution system consists of a PV generator as a DC source, DC loads, and lithium-ion batteries as the ESS. The PID controller, which was covered in the modeling section, provides the foundation for managing the electricity between the PV generator and the lithium-ion batteries. It should be noted that the bipolar LVDC distribution voltage is assumed equal to \(\pm\) 320 V. In fact, the LVAC distribution in this test system has a line-to-line voltage of 400 V and a frequency of 50 Hz, which consists of a wind turbine and AC loads. In this test system, an HVDC distribution with a voltage equal to 20 kV is presented thanks to the presence of a transformer with a power of 250 MVA and a power converter. Additional real data and configuration settings for the test system's four buses--LVDC, HVDC, LVAC, and the electrical grid--are summarized in Table 1. \begin{table}
\begin{tabular}{c c} \hline \hline \multicolumn{2}{c}{**System Parameters**} \\ \hline Constant distribution line & Reactance = 0.26 \(\Omega\)/km \\  & Resistance = 0.164 \(\Omega\)/km \\ \hline Photovoltaic generator & Output power = 10.5 kW \\  & Output voltage = 320 VDC \\ \hline ESS & Output voltage = 297 VDC \\  & Capacity = 50 AH \\ \hline Wind & Output power = 1.5 MW \\  & Output voltage = 575 VAC \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Proposed test system parameters. Figure 11: Modeled representation of load. In this study, a PV generator with a power output of 10.5 kW was employed. The six modules that constitute the PV generator were connected in series using seven parallel strings. The customized PV array type was the Advance Power API-M250, as shown in Figure 13.  
The most prevalent types of energy storage utilized in standalone PV systems are lead acid batteries and lithium-ion batteries. Low power density and high energy density  
Figure 12: Four buses novel hybrid network test. Figure 13: Relevant PV generator characteristics. combine to provide energy-storage batteries with moderate charge/discharge rates. In terms of performance, lead-acid battery losses are substantially larger at 15-20%, whereas Li-ion battery losses are generally much lower at 2-8%. Another drawback of lead-acid batteries is that they require more time to charge than do Li-ion batteries. As a result, in this study, Li-ion batteries with the properties shown in Figure 14 were employed as the ESS. It is noted that in order to testify to the high performance and efficiency of the novel hybrid network test, a real profile of irradiation and temperature over 24 h was used in this study, as shown in Figure 15.  
Figure 14: Relevant Li-ion current discharge characteristics. Figure 15: PV generator characteristics. (**a**) irradiation, (**b**) temperature. It should be noted that the test system uses an underground cable model. Because the subterranean cable's conductor resistance is lower in this instance compared to the overhead distribution line, there is less voltage drop. A bipolar LVDC distribution network system was used in this work. This bipolar system consists of three voltage levels, which are: positive-to-ground, negative-to-ground, and pole-to-pole. The voltages of the first and second DC loads used in the LVDC distribution are shown in Figure 16. Based on this figure, it is possible to verify that a constant positive pole (320 V) and negative pole (\(-\)320 V) are supplying DC loads 1 and 2, respectively.