An Investigation into the Constraints of Reactive Power Output in Contemporary Photovoltaic Inverters

Abstract

The rise in photovoltaic (PV) system adoption has suggested incorporating intelligent functionalities into PV
inverters to replicate the grid support functions seen in traditional power plants. One such function involves using
PV inverters for static and dynamic reactive power injection for grid voltage stabilization. Different control
strategies for managing reactive power have been explored, showcasing precise and rapid control capabilities.
However, discussions on the limitations of reactive power output still need to be completed. Variations in
semiconductor behavior between actual and reactive power injection result in differing output capacities for
reactive power. This investigation compares the maximum reactive power capabilities of three standard PV
inverter designs: 2-level full bridge, 3-level Neutral Point Clamped (NPC), and T-type Neutral Point Clamped
(TNPC). The study notes that PV inverters generally exhibit greater reactive power capacity than absolute power.
This attribute is advantageous for improving intelligent PV inverters' grid voltage support function. Consequently,
based on these findings, a novel model is proposed, which constrains apparent power to aid the reactive power
dispatch controller.