  This paper focuses on the effective use of smart inverters for Volt/Var
control (VVC) on a distribution system. New smart inverters offer Var support
capability but for their effective use they need to be coordinated with
existing Volt/Var schemes. A new VVC scheme is proposed to facilitate such
coordination. The proposed scheme decomposes the problem into two levels. The
first level uses Load Tap Changer (LTC) and Voltage Regulators (VRs) and
coordinates their control with smart inverters to adjust the voltage level on
the circuit to keep the voltages along the circuit within the desired range.
The second level determines Var support needed from smart inverters to minimize
the overall power loss in the circuit. The results of the supervisory control
are sent to the devices which have their local controllers. To avoid frequent
dispatch, smart inverters are supervised by shifting their Volt/Var
characteristics as needed. This allows for the smart inverters to operate close
to their optimal control while meeting the limited communication requirements
on a distribution system. A case study using the IEEE 34 bus system shows the
effectiveness of this supervisory control scheme compared to traditional
volt/var schemes.
