Using PV inverters for voltage support at night can lower grid costs

Abstract

Areas with sparse transmission lines are common in regions with high solar energy potential and need voltage support. This may require installing expensive voltage compensators, such as static synchronous compensators (STATCOMs). This expense can increase the cost and decrease the acceptance of large-scale adoption of solar power. Unlike current photovoltaic (PV) inverter controllers, which provide voltage support only during the day, commercially available augmented voltage controllers can provide voltage support at night. We examine whether PV inverters improve nighttime voltage on the grid and how much such an operation would cost compared to a STATCOM. We ran grid contingency analyses on a model for West Texas within the Electric Reliability Council of Texas (ERCOT) jurisdiction under spring and summer conditions to determine if PV inverters can support nighttime voltage under varying reactive power demand. The cost of reactive power has not been defined previously, especially in the context of the United States. Our methods and application provide a way to determine the cost of reactive power for both PV project developers and system planners. Allowing PV inverters to provide reactive power can reduce system costs by millions of dollars, or 4–15 times less costly than installing a STATCOM. We determined inverter voltage support costs by calculating the cost of earlier inverter replacements due to increased reactive power output and voltage controllers. The net system savings argue for ERCOT changing their voltage support policies to incentivize PV plants to provide voltage support at night.