Systemwide Auto Volt Control

Perform wide-area voltage control through closed loop control by measuring the wide area voltages, computing a control solution, and effecting wide area control

System wide voltage and subsequent power flow can be optimized by looking at the voltage profile for a large segment of the power grid, choosing set-points for the voltages at the various control points, and issuing the appropriate control commands to effect the desired operating point.

Prior to starting the voltage control process, the system would need to determine the availability (in/out of service) and capacity of all the control points around the system. This information would then have to be factored into the voltage control algorithm. For example, if part of a series capacitor bank is out of service, the remaining available series impedance shall be reported; if an SVC is out of service, this shall be reported to the Controller.

Voltage (phase and sequence) from 10 to a few hundred points around the power system are to be measured and transmitted to one or more Controllers located around the power system. Each Controller analyzes the measured voltages and computes an optimal voltage control solution. The control solution would include linear control of generator voltage and synchronous condenser outputs, transformer tap changer control, voltage regulator control, Thyristor controlled Series Capacitor (TCSC) control, Static Var Capacitor control, DC link power flows, as well as on/off control of series and shunt capacitor banks and reactor switching. A measure/control link to DER/ADA/Consumer/Industrial devices is also envisioned that would enable some voltage support/load shed (in emergency conditions) from the distribution system. Upon issuance of the control command, the device receiving the command shall acknowledge that the voltage control command was received and subsequently executed.

This devices in this scenario would also be used for Voltage Security (see Voltage Security use case) and the steps for Voltage Security are called out as an alternate sequence in the function steps.

On failure of the communication system to a particular node, that node shall resort to local voltage control with previously calculated set-points. Failure of communication to any remote node shall be immediately (within 1 second) to the system operator and other monitoring points as desirable.

Steps

Normal Sequence Steps

#	Event	Name of Process/Activity	Description of Process/Activity	Information Producer	Information Receiver	Name of Info Exchanged	IntelliGrid Architecture Environments
1.1	System Initialization	Initialization	System operator starts the automatic voltage control process	Controller	Controllable Device	Initialization data; configuration data	Non Critical DAC
1.2	Programmed data rate	Measure System Voltage	Measure system voltage and stream to Phasor Data Concentrator	Phasor Measurement Unit	Phasor Data Concentrator	Phasor Data stream	Inter-Field Equipment
1.3	Programmed data rate	Aggregation	Aggregate phasor data streams from multiple Phasor Measurement Unit sources	Phasor Data Concentrator	Controller	Aggregated Phasor Data	Non Critical DAC
1.4	Programmed data rate	Decision	Manipulation of phasor data to determine the control required to implement the optimal system voltage	Controller	Controllable Device	Control information	Non Critical DAC
1.5	Programmed data rate	Acknowledge	Acknowledge that the Controllable Device received the control command and were able to execute as requested	Controllable Device	Controller	Status information	Non Critical DAC

Steps – Alternative / Exception Sequences

#	Event	Name of Process/Activity	Description of Process/Activity	Information Producer	Information Receiver	Name of Info Exchanged	IntelliGrid Architecture Environments
2.1	Large system voltage angle detected	Angle Check	Check the difference of the angles of the voltages across the system	Controller	Regional System Operator; Voltage Security Controller	Voltage Security alarm; Voltage angle difference	Non Critical DAC
2.2	Large system voltage angle detected	Voltage Security Control	Determine the corrective action to be taken upon detection of a voltage security issue	Voltage Security Controller	Controller	System phase angles	Non Critical DAC
2.3	Large system voltage angle detected	Issue Control Action	Issue the control actions to the controllable elements around the system	Controller	Controllable Device	Control	Non Critical DAC
2.4	Control action received	Acknowledge	Acknowledgement that the control action has been received and executed	Controllable Device	Controller	Control Acknowledge	Non Critical DAC

Transmission Operations - System-wide Automatic Voltage Control Function

Contents

Narrative

Steps

Normal Sequence Steps

Steps – Alternative / Exception Sequences