Designing conservative solar inverter standards to increase resilience

Solar power plants have proliferated over the past decade and are projected to double their capacity over the next five years. One of the primary challenges associated with solar grids is adapting to the changes in sunlight caused by clouds and sun cycles. Clouds reduce the amount of sunlight that reaches the solar panels, but sometimes they can amplify it significantly in a process known as cloud edge enhancement. If this sudden increase in sunlight is not managed correctly, it can result in high currents that, in rare cases, can be problematic for utility-scale solar Photovoltaic (PV) plants.

Zamora Zapata et al. suggested new industrial standard designs for inverters that can make PV plants more robust to sunlight amplification regardless of control strategies.

“In general, hourly solar data is used to design inverters,” said author Mónica Zamora Zapata. “Designers tend to neglect such irradiances since the spikes only last a few seconds or minutes.”

The team simulated expected PV output in standard cells by using ten years of one-minute solar data from 7 stations across the US under 12 different configurations. They found that the current industry standard inverter with a specified maximum current of 125% of the rated current should be increased to 200%. Applying this would make plants more robust to spiking solar radiation events.

“For the future, we would like to observe the actual inverter control and determine how it can be improved,” said Zamora. “We would also like to know how much our results would change if we used one-second resolution data instead of one-minute.”

Source: “Comparing solar inverter design rules to subhourly solar resource simulations,” by Mónica Zamora Zapata, Kari Lappalainen, Adam Kankiewicz, and Jan Kleissl, Journal of Renewable and Sustainable Energy (2023). The article can be accessed at https://doi.org/10.1063/5.0151042 .