Traditionally, capacitance measurement is carried out using pulse solar simulator. During short pulse illumination, usually 1.5 ms, the electronic equipment switches part / string from short circuit to open circuit and generates step response dvldt. The step response is monitored and recorded by a storage oscilloscope and an X-Y plotter.
Synchronous step response measurement in the stable part of pulse illumination is the main requirement of pulse solar simulator and electronic switching device.
The section level capacitance measurement data from traditional silicon solar cells meet the interface requirements of power management system with sufficient margin. Therefore, no possible measurement errors were detected and no further investigation is required.
Incorrect oscilloscope time base setting or using an oscilloscope with insufficient bandwidth may significantly overestimate the capacitance value due to aliasing.
The step response measurement of the solar cell string and part shows oscillation because the wiring inductance is initially charged with magnetic energy. This second-order effect can be reduced by switching the low-pass filter network on the drain source of MOSFET, but it will introduce measurement error.
The peak voltage of oscillation may be higher than the allowable limit of components in the grid. Therefore, it is recommended to use zener diodes to limit this voltage. Zener diode and fitting curve through V-T curve with violent oscillation will introduce errors in capacitance calculation, which is the worst case relative to the actual capacitance value. The capacitance measurement program described in this paper has sufficient accuracy to demonstrate a reliable power management system interface.
The capacitance of multi junction GaAs solar cells is higher than that of silicon solar cells. According to the test results, the capacitance of multi junction GaAs solar cells is usually more than 4 times higher than that of silicon solar cells under the condition of balancing the same cross-section current.