In order to maintain a stable grid voltage, it is desired that inverters be able to supply or absorb reactive power to/from the grid. One way to achieve this is to have the inverter supply or absorb reactive power in response to fluctuations in grid voltage. HECO RULE 14H/CPUC RULE 21 is requiring all certified grid-support inverters, or smart inverters, shall support a Volt/VAr auto-regulation function.
In this mode, the reactive power will be regulated by a curve of reactive power versus grid voltage automatically. The registers or setpoints for regulating System reactive power and PF will be both ignored by the inverter.