Photovoltaic hot spot mitigation using voltage-threshold control at the panel level

Maximum power point tracking (MPPT) for photovoltaic (PV) panels is primarily implemented at the panel level in presently-installed PV systems. Each panel typically consists of three subpanel strings with a bypass diode connected over each subpanel. When a panel becomes partially-shaded, the MPPT control may bypass a substring to optimize power, however, bypassing increases hot spotting risk. This paper introduces a voltage-threshold control that works with existing MPPT to mitigate hot spotting. The control imposes a lower voltage limit that prevents a compromised subpanel string from being bypassed. Simulation results show that voltage-threshold control is effective in limiting hot spotting for both typical Type A and Type B PV cells, with only minimal reduction in energy output.