因此，我尝试使用sandia_fit 函数将功率逆变器模型拟合为多项式函数。
我每小时都有来自逆变器的 ac_power、dc_power、dc_voltage 读数。这三个参数以及 dc_voltage_level 是 fit_sandia 函数的类数组输入，该函数将逆变器模型多项式逼近到给定数据。
分析了 pvlib.pvsystem.retrieve_sam 各种数据库后，很明显 C0、C1、C2 和 C3 应该是非零值，但是，无论我从时间序列数据中尝试什么输入，sandia_fit 只返回 C0 作为非零值并且C1、C2、C3 为 0。
一个例子会很方便，如何正确使用这个功能。谢谢！
编辑：
dc_power = [0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,396.75,1150.56,1426.36,1577.72,1566.14,1842.39,877.96,415.15,307.07,0.0,0.0,0.0,0.0,0.0,0.0.0. ,0.0,0.0,0.0,0.0,0.0,0.0,0.0,229.16,927.67,2059.07,2914.16,4288.43,4224.21,2477.9,1548.42,874.56,226.03,0.0,0.0,0.0,0.0,0.0,0.0. ,0.0,0.0,0.0,0.0,0.0,0.0,0.0,524.2,1131.62,2999.88,5863.7,4969.04,4334.98,2033.0,862.03,346.04,0.0,0.0,0.0,0.0,0.0,00.0,0.0,0. ,0.0,0.0,0.0,0.0,0.0,0.0,0.0,600.61,675.67,941.0,629.99,1119.77,692.0,347.6,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0]
ac_power=[0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,195.92,1017.58,1353.08,1493.0,1336.58,1693.58,793.27,286.75,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0, ,0.0,0.0,0.0,0.0,0.0,0.0,0.0,23.33,875.83,1971.25,2796.25,4218.42,4006.58,2280.08,1429.25,718.25,21.2,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0. ,0.0,0.0,0.0,0.0,0.0,0.0,0.0,270.25,1088.67,3178.67,6553.92,4798.25,3962.08,1854.5,720.92,59.3,0.0,0.0,0.0,0.0,0.0,00.0,0.0,0.0. ,0.0,0.0,0.0,0.0,0.0,0.0,4.42,483.75,595.08,829.67,527.42,1031.0,540.5,178.58,0.0,0.0,0.0,0.0,0.0,0.0,0.0,0.0]
dc_voltage=[25.06,25.06,25.06,25.06,25.06,25.06,25.06,73.12,658.29,747.35,747.42,747.72,747.75,747.73,747.81,747.59,290.79,25.11,25.08,25.07,25.06,25.06,25.06,25.06 ,25.06,25.06,25.05,25.06,25.05,25.05,25.05,229.67,747.51,747.46,747.3,747.6,747.51,747.48,747.58,747.63,339.99,25.07,25.06,25.06,25.07,25.06,25.06,25.06,25.06 ,25.06,25.06,25.06,25.07,25.07,25.07,113.24,611.16,747.81,747.66,747.23,747.34,747.68,747.57,747.31,417.04,25.15,25.12,25.12,25.11,25.12,25.12,25.1,25.12,25.11 ,25.12,25.11,25.12,25.12,25.12,53.7,297.61,747.57,747.38,747.68,747.66,747.62,747.3,726.89,93.88,25.14,25.12,25.12,251.12,25.12]