Assessment of Personal Safety Concerns of Plug and Play Photovoltaic Inverters using a Black Box Approach and Laboratory Measurements

The rising utilization of plug and play photovoltaic systems has sparked safety concerns, particularly when installed by non-professionals, as current standards only partially address these issues. This paper introduces a black box testing method to evaluate the personal safety of plug and play inverters. 25 microinverters are assessed using three tests: (1) residual voltage behavior at the mains plug following disconnection, (2) current increase with low grid voltage, and (3) maximum touch temperature during operation. Results indicate 56% of inverters comply with the proposed German plug and play standard, performing comparably to other electrical devices. Further investigation is necessary to determine if exceeding this threshold poses a direct safety threat. A correlation has been identified between the output parameters of the inverters (resistance and capacitance) in the unplugged state and the duration required to reach safe voltage levels for most devices. The integration of a relay, however, can ensure compliance across all devices. During low voltage conditions, current surges are recorded, which could strain non-dedicated circuits. The temperature test reveals a positive correlation between the power density of inverters and their touch temperature. The outcomes of this study offer insights and guidance for future standardization and product improvements.