PERFORMANCE ANALYSIS OF SOLAR INVERTERS UNDER LIGHTNING-INDUCED SURGES

Abstract:
This study presents an experimental analysis investigating the influence of surge protection devices (SPD) on prolonging the operational lifespan of inverters utilized in residential solar energy generation systems. Two distinct models of photovoltaic inverters with nominal power of 3kW, denoted as 'A' and 'B' and sourced from different manufacturers, underwent a series of successive electrical pulses to assess their resilience with and without external SPD protection. The experiments involved subjecting the inverters to a maximum of 100 electrical pulses, each not exceeding 4kA of current. These pulses were applied differentially to the Direct Current (DC) input and in common mode to the Alternating Current (AC) output of the inverters. Results indicated that, at the AC output, Models 'A' and 'B' demonstrated an average endurance of 5 and 7.7 pulses, respectively. Conversely, at the DC input, Model 'A' exhibited an average failure after 1 surge, while Model 'B' sustained up to 6 surges on average. When equipped with external SPD protection, both models exhibited resilience, withstanding the full 100 pulses on both the DC and AC sides. An examination of circulating currents revealed that the SPD effectively diverted at least 93.6% of the energy that would otherwise reach the inverter. This underscores the paramount importance of employing external SPD to safeguard these inverters, as evidenced by the enhanced resilience demonstrated in the presence of surge protection.