Comparison of different Anti-PID techniques for Grid-Tied Isolated Solar Inverters

Abstract

Potential Induced Degradation (PID) effect in solar Modules came as a huge surprise to the solar PV industry as a whole. PID is caused by the high potential difference with respect to earth. This work compares different anti PID techniques being used in strings and central inverters. PID effect can be eliminated by raising the potential of negative side of DC link to positive with respect to ground. These techniques are possible for grids connected inverters which are isolated from the grid by medium voltage transformer. In string inverters, it is done by lifting the negative of DC link from DC side, lifting the DC link negative from the AC side by forming virtual neutral point, PID recovery at night. In central inverter the negative of the DC link is grounded directly /with a resistor to counter attack PID effect. Here four techniques are compared namely anti PID from DC side string inverter, anti PID from AC side of string inverter and anti PID by negative grounding in central inverter, Anti-PID recovery function in central inverters. In all the four cases simulation is done in both MATLABSimulink ®/ LT SPICE software and results will be compare to understand the merits and demerits. To Validate the Discussion Simulation Results and Validated Practical data are provided for both String and Central Inverter.