pvanalytics.features.snow.categorize#
- pvanalytics.features.snow.categorize(transmission, measured_voltage, modeled_voltage_with_snow, modeled_voltage_no_snow, min_dcv, max_dcv, threshold_vratio, threshold_transmission)#
Categorizes electrical behavior into a snow-related mode.
- Parameters
transmission (array-like) – Fraction of plane-of-array irradiance that can reach the array’s cells through the snow cover. [dimensionless]
measured_voltage (array-like) – Measured DC voltage. [V]
modeled_voltage_with_snow (array-like) – DC voltage modeled using measured plane-of-array irradiance reduced by calculated transmission. [V]
modeled_voltage_no_snow (array-like) – DC voltage modeled using measured plane-of-array irradiance and assuming transmission equals 1. [V]
min_dcv (float) – The lower voltage bound on the inverter’s maximum power point tracking (MPPT) algorithm. [V]
max_dcv (float) – The upper voltage bound on the inverter’s maximum power point tracking (MPPT) algorithm. [V]
threshold_vratio (float) – The lower bound for vratio that is representative of snow-free conditions. Determined empirically. Depends on system configuration and site conditions. [unitless]
threshold_transmission (float) – The lower bound on transmission that is found under snow-free conditions, determined empirically. [unitless]
- Returns
mode (array-like) –
modeisNonewhen any of the inputs used to determinemodeisnan.vmp_ratio (array-like) – Ratio between measured DC voltage and DC voltage modeled with calculated transmission.
Notes
Modes are defined in 1:
Mode 0: Indicates periods with enough opaque snow that the system is not producing power. Specifically, Mode 0 is when the measured voltage is below the lower bound of the inverter’s MPPT range but the voltage modeled using measured irradiance and ideal transmission is above the lower bound of the inverter’s MPPT range.
Mode 1: Indicates periods when the system has non-uniform snow which affects all strings. Mode 1 is assigned when both operating voltage and current are reduced. Operating voltage is reduced when snow causes mismatch and current is decreased due to reduced transmission.
Mode 2: Indicates periods when the system has non-uniform snow which causes mismatch for some modules, but doesn’t reduce light transmission to other modules.
Mode 3: Indicates periods when the the system has snow that reduces light transmission but doesn’t create mismatch. Operating voltage is consistent with snow-free conditions but current is reduced.
Mode 4: Voltage and current are consistent with snow-free conditions.
Mode -1: Indicates periods where it is unknown if or how snow impacts power output. Mode -1 includes periods when:
Voltage modeled using measured irradiance and ideal transmission is outside the inverter’s MPPT range, OR
measured voltage exceeds the upper bound of the inverter’s MPPT algorithm.
Mode -1 is added in this function to cover a case that was not addressed in 1.
Mode is None when measured values (voltage, current, irradiance or temperature) are either missing or produce modeled voltage that is invalid.
References
- 1(1,2)
E. C. Cooper, J. L. Braid and L. M. Burnham, “Identifying the Electrical Signature of Snow in Photovoltaic Inverter Data,” 2023 IEEE 50th Photovoltaic Specialists Conference (PVSC), San Juan, PR, USA, 2023, pp. 1-5, DOI: 10.1109/PVSC48320.2023.10360065.
