Determining circuit model parameters from operation data for PV system degradation analysis: PVPRO

• Published in: Solar energy 2023-04, Vol.254, p.168-181
• Main Authors: Li, Baojie, Karin, Todd, Meyers, Bennet E., Chen, Xin, Jordan, Dirk C., Hansen, Clifford W., King, Bruce H., Deceglie, Michael G., Jain, Anubhav
• Format: Article
• Language: English
• Subjects: Degradation; Health monitoring; Parameter estimation; Photovoltaic; Single-diode model
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2023.03.011

•A comprehensive methodology (PVPRO) is proposed to extract the time evolution trends of key PV parameters only using easily accessible operation and environmental data.•PVPRO well captures the degradation trends of IV and equivalent model parameters on the synthetic datasets.•PVPRO is robust to measurement noise and the presence of faults on the synthetic datasets.•A demonstration of PVPRO is given on a field 271 kW PV system.•An open-source Python package is available to perform the analysis (https://github.com/DuraMAT/pvpro) Physics-based circuit parameters like series and shunt resistance are essential to provide insights into the degradation status of photovoltaic (PV) arrays. However, calculating these parameters typically requires a full current–voltage characteristic (I-V curve), the acquisition of which involves specific measurement devices and costly methods. Thus, I-V curves of the PV system level are often not available. This paper proposes a methodology (PVPRO) to estimate these I-V curve parameters using only operation (string-level DC voltage and current) and weather data (irradiance and temperature). PVPRO first performs multi-stage data pre-processing to remove noisy data. Next, the time-series DC data are used to fit an equivalent circuit single-diode model (SDM) to estimate the circuit parameters by minimizing the differences between the measured and estimated values. In this way, the time evolutions of the SDM parameters are obtained. We evaluate PVPRO on synthetic datasets and find an excellent estimation of both SDM and the key I-V parameters (e.g., open-circuit voltage, short-circuit current, maximum power, etc.) with an average relative error of 0.55%. The performance, especially the extracted degradation rate of parameters, is robust to various measurement noises and the presence of faults. In addition, PVPRO is applied to a 271 kW PV field system. The relative error between the real and estimated operation voltage and current is less than 1%, suggesting that degradation trends are well captured. PVPRO represents a promising open-source tool to extract the time-series degradation trends of key PV parameters from routine operation data.