Simultaneous Non-contact I-V (NCIV) Measurements of Photovoltaic Substrings and Modules in a String

This paper presents a non-contact approach to obtain simultaneous current-voltage (I-V) curves of photovoltaic (PV) substrings and modules in a string without the need of disconnecting the individual modules from the string. There are two types of I-V curve tracers currently available in the marketplace, capacitor-based and electronic load-based. The primary requirement of these conventional I-V tracers is the disconnection of individual modules in the string so that the individual modules can be connected through the connectors of the individual modules. These conventional contact-tracers have three major limitations in the utility scale power plants: safety during disconnecting and reconnecting field-aged module connectors, extensive time and hardship of test personnel and limited availability of clear sunny hours/days to obtain I-V curves of 1000s of modules in the field. To mitigate all these three limitations, we experimented with a non-contact I-V (NCIV) tracer approach. In this approach, we utilized an electrostatic voltmeter (ESV) in combination with a voltage probe and a hall sensor to obtain I-V curves. A major application of the NCIV tracer is that it can instantaneously identify the underperforming modules in a string without the need of disconnecting the individual modules and translating the measured I-V curves to standard reporting conditions such as STC (standard testing conditions) because all the modules in the string are simultaneously measured at a single prevailing weather condition of irradiance, temperature, wind speed and wind direction.