## 3 Description of Problem Phenomenon and Theoretical Analysis
### Theoretical Calculation  
Taking the MEO orbiting satellite described in Phenomena 1 and 2 as an example, the parameter table of the satellite's solar cells is shown in Table 2.  
The design parameters of the solar cell circuit for this satellite are shown in Table 3 below:  
The satellite has 12 sub-arrays, with each sub-array consisting of 16 cells in parallel. Theoretically, based on the number of parallel single-cell panels in each sub-array and temperature changes, the variation in the output current of the entire wing under such conditions can be analyzed.  
According to on-orbit data, when a sub-array is in the shunt state, the average temperature of the array is about 53 \({}^{\circ}\)C; when the sub-array is in the power supply state, the average temperature of the array is about 38 \({}^{\circ}\)C.  
According to Formula (2):  
\[I=\left[I_{mp}+S\cdot\beta_{i}\cdot(T-25)\right]\cdot K_{Azh}\cdot K_{Acs} \cdot K_{Afz} \tag{2}\]  
In the formula:  
\(I_{mp}\): Optimum operating point current of a single solar cell at the beginning of life (17.13 mA/cm\({}^{2}\));  
\begin{table}
\begin{tabular}{c c} \hline
**Parameters** & **Value** \\ \hline Short-circuit Short-circuit \(I_{\mathrm{sc}}\) & 17.67 mA/cm\({}^{2}\) \\ Open-circuit voltage \(V_{\mathrm{oc}}\) & 2.7 V \\ Optimum operating point current \(I_{\mathrm{mp}}\) & 17.13 mA/cm\({}^{2}\) \\ Optimum operating point voltage \(V_{\mathrm{mp}}\) & 2.396 V \\ Fill factor \(FF\) & 0.86 \\ Photoelectric conversion efficiency \(\eta\) & 30\% \\ Absorptivity: \(\alpha_{S}\) & \(\leq\)0.92 \\ Hemispherical emissivity: \(\epsilon_{H}\) & 0.82 \(\pm\) 0.03 \\ Dimension specification & 39.8 mm \(\times\) 60.4 mm \(\times\) 0.175 mm \\ \hline \end{tabular}
\end{table}
Table 2: Electrical parameters table of solar cells.  
\begin{table}
\begin{tabular}{c c} \hline
**Parameters** & **Value** \\ \hline Circuit and diode voltage drop & 3 V \\ Current combination loss factor & 0.98 \\ Current electrical performance test error factor & 0.98 \\ Current particle irradiation degradation factor & 0.91 \\ Current ultraviolet radiation loss factor & 0.98 \\ Current temperature coefficient & 0.006 mA/cm\({}^{2}\)\({}^{\circ}\)C\(\sim\)0.014 mA/cm\({}^{2}\)\({}^{\circ}\)C \\ \hline \end{tabular}
\end{table}
Table 3: The relevant parameter table adopted for the design of the solar cell circuit.  
\(S\): Area of the solar cell (39.8 mm \(\times\) 60.4 mm); \(\beta_{i}\): Current temperature coefficient (0.014 mA/cm\({}^{2}\)\({}^{\circ}\)C); \(T\): Operating temperature for current; \(K_{Azh}\): Current ultraviolet radiation loss factor (0.91); \(K_{Acs}\): Current combination loss factor (0.98); \(K_{Afz}\): Current particle irradiation degradation factor (0.98). Through calculation, the changed current is (\(53-38\)) \(\times\) 4 \(\times\) 6 \(\times\) 0.010 \(\times\) 16 \(\times\) 8 = 460.8 mA, which is basically consistent with the actual fluctuation of 0.5 A. The reasons for the difference are as follows: first, the selection difference in the current coefficient \(\beta_{i}\); second, the number of working state adjustments of the eight sub-arrays is different from the theoretical situation (a certain circuit is in the adjustment state with a certain duty cycle). At the same time, the sun-earth distance factor will also affect the results. Due to the change in the solar angle, the current intensity of the solar panel on the negative Y-wing changes, and the temperatures of the three thermistors all change significantly, with the fluctuation trend consistent with the current of the negative Y-wing solar panel.