# Design of a Power Converter for Solar Energy Storage System
## 3 Design and Experimental Results
### Experimental Waveforms and Measurements  
The actual measured waveform of the DC grid port supplied by the battery port, with a phase shift angle \(\varphi\) of 118.8 degrees, is shown in Figure 10. This figure includes the trigger control signals of four switches, battery voltage, battery output current, voltage and current on both sides of the transformer, and the DC port voltage and incoming DC port current. It can be seen from Figure 10 that the battery terminal voltage \(V_{bat}\) is 280.1 V, the average current flowing out of the battery terminal \(I_{bat}\) is 1.875 A, the DC port voltage is 398.5 V, and the average current flowing into the DC port is 1.203 A. The converter efficiency can be obtained by Equation (23), and the calculated result is 91.2% in this experiment. The current flowing into the DC port under different phase shift angle operations is shown in Figure 11. Finally, the relationship between the conversion power and efficiency of the DC grid port supplied by different battery voltages is shown in Figure 12.  
\[\eta=\frac{P_{DC\ Grid}}{P_{bat}}=\frac{V_{DC\ Grid}\times I_{DC\ Grid}}{V_{ bat}\times I_{bat}}=\frac{398.5\times 1.203}{280.1\times 1.875}=\frac{479.39}{525.19}=91.2\% \tag{23}\] \begin{table}
\begin{tabular}{c c} \hline \hline
**Component Parameter and Symbol** & **Value** \\ \hline Voltage-boost inductors \(L_{1},L_{2}\) & 81 \(\upmu\)H \\ transformer turn ratio \(N_{p}\):\(N_{S}\) & 1:1.678 \\ transformer leakage inductance \(L_{k}\) & 16 \(\upmu\)H \\ Battery port energy storage capacitor C\({}_{bat}\) & 330 \(\upmu\)F \\ DC grid capacitor C\({}_{Grid}\) & 810 \(\upmu\)F \\ Power switches \(S_{1}\)-\(S_{8}\) & C2M0160120D \\ Gating signal controller & TMS320F28335 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Component and device parameters. Figure 13 shows the actual measured waveform of the battery port stored from the DC grid port, with a phase shift angle \(\varphi\) of 108 degrees. According to this figure, the DC port voltage is 400.2 V, the average current flowing out of the DC port is 1.043 A, the battery terminal voltage \(V_{bat}\) is 287.9 V, and the average current \(I_{bat}\) flowing into the battery terminal is 1.301 A. The converter efficiency is 89.7%--calculated by Equation (24). The current flowing into the battery port under different phase shift angle operations is shown in Figure 14. Finally, the relationship between the conversion power and efficiency of energy storage with different battery voltages is shown in Figure 15.  
\[\eta=\frac{P_{bat}}{P_{DC\_Grid}}=\frac{V_{bat}\times I_{bat}}{V_{DC\_Grid} \times I_{DC\_Grid}}=\frac{287.9\times 1.301}{400.2\times 1.043}=\frac{374.55}{4 17.40}=89.7\% \tag{24}\]  
Figure 11: Power regulation curve in the B2D mode. Figure 12: Efficiency curve in the B2D mode. Figure 14: Energy regulation curve for the D2B mode. Figure 16 displays the waveform of the stored energy from the renewable energy port to the battery port, with a duty cycle of 53.3%. This waveform exhibits that the renewable energy port voltage is 140.0 V and the average current leaving the port is 3.719 A. Moreover, the battery terminal voltage \(V_{bat}\) is 287.4 V, and the average current flowing into the battery port is 1.703 A. The converter efficiency is 94%--calculated by Equation (25). The current flowing into the battery port under different duty cycles is shown in Figure 17. Finally, the relationship between the conversion power and efficiency of different energy stored from the renewable energy port is shown in Figure 18.  
\[\eta=\frac{P_{bat}}{P_{reg}}=\frac{V_{bat}\times I_{bat}}{V_{reg}\times I_{reg} }=\frac{287.4\times 1.703}{140.0\times 3.719}=\frac{489.44}{520.66}=94\% \tag{25}\]  
Figure 19 illustrates the actual measured waveform that represents the transfer of energy from the renewable energy port to the DC port. The waveform has a phase shift angle of 133.2\({}^{\circ}\) and a duty cycle of 44%.