Effects of I-V Measurement Parameters on the Hysteresis Effect and Optimization in High-Capacitance PV Module Testing

In high-efficiency crystalline silicon photovoltaic (PV) modules, the internal capacitance may lead to a strong hysteresis effect in current-voltage (I-V) measurements. This hysteresis introduces a significant error in measurement results. This work investigates the nature of the hysteresis error (epsilon) variation caused by different measurement parameters in the I-V measurement. The effects of the I-V measurement parameters on the hysteresis error of a silicon heterojunction PV module were investigated through some comparative tests. Among all the parameters, the number of sweep points (N) and the voltage hold time (T-h) of each sweep point are the most important factors affecting the value of the hysteresis error in I-V measurements. With the same total T-h, the epsilon variation canbe expressed as a single-peak curve with the increase of N. With the same T-h for each point, epsilon increases in proportion to the reciprocal of N. To explain the origin of the theoretical relation among e, T-h, and N, an analytical equation was derived according to the diode model circuit and first-order circuit analysis method. Based on the derived equation, a parameter-setting optimization method for high-capacitance PV module measurements is proposed to precisely control the hysteresis error through certain simple pretests.