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236 CHAPTER 7 Strategies for Fault Detection and Diagnosis

Table 7.2 Main Parameters Included in the Monitoring System
PV System
Monitored Parameters Components Sensors
Climatic Irradiance in the PV PV modules, Pyranometers, reference
parameters array plane strings, and arrays solar cells
Module and ambient Thermocouples, resistive
temperature temperature sensors
Humidity Humidity sensors
Wind speed Thermal wind sensors and
Barometric pressure anemometers
Pressure sensors
Electrical AC and DC: voltage, PV strings and Voltmeters
parameters Current and power arrays Ammeters, hall sensors, or
Frequency and Inverters active-type CT
power factor (AC) Power meters, power
analyzers

Some centralized supervision systems use as input data satellite monitoring data or
weather forecast data [17e19] for the site where the PV system under supervision is
located to evaluate the expected energy production and yields. Moreover, for very
short-term forecasts, stochastic learning techniques and artificial intelligence
methods can be applied [20e23]. Satellite images [24] or local ground measure-
ments of cloud speed [25] can also be used to analyze cloud motion vectors for
forecasting.
The best accuracy in the supervision and diagnosis of PV systems is achieved by
using real monitored data in combination with specific software tools in both
centralized and distributed supervision systems. The monitored data can be grouped
in climatic and electrical parameters as shown in Table 7.2.
The most important climatic parameters are the plane of array (POA) irradiance
and the PV module temperature. Moreover, relative humidity, barometric pressure,
and wind speed also affect the behavior of PV modules and can be included in the
monitoring system.
Regarding the electrical parameters, voltages, currents, and power must be moni-
tored at both DC and AC sides of the PV system. It is also important to measure the
frequency, power factor, and total harmonic distortion (THD) at the output of the in-
verters in GCPVSs.
Specific sensors together with data acquisition systems or data loggers can be
used for monitoring both electrical and climatic parameters. However, nowadays
most inverters include inputs for irradiance and temperature sensors and internal
hardware to measure all electrical parameters at its input (DC) and output (AC)
and for maximum power point tracking (MPPT) evolution. Moreover, most inverters
also include storage capabilities and communication interfaces: Ethernet, RS-485,
RS-232, or wireless connection (Bluetooth, Wi-Fi, and GSM), to send the monitored
data to the supervision system.