Capacitor

Capacitors are used for reactive power compensation and voltage support scenarios. The capacitor implements a switchable set of capacitors. capacitor objects are one of two objects in the powerflow module that incorporate a form of automatic control. To take full advantage of this functionality, simulations of greater than one time step (time-varying simulations) are recommended. Single-phase powerflow connections (phase S) are not supported by capacitors at this time.

For technical details on capacitor modeling, see Controls and Devices Theory. A typical capacitor implementation is

object capacitor {
    phases ABCN;
    name CapNode;
    phases_connected ABCD;
    control MANUAL;
    capacitor_A 0.5 MVAr;
    capacitor_B 0.5 MVAr;
    capacitor_C 0.5 MVAr;
    control_level INDIVIDUAL;
    switchA OPEN;
    switchB OPEN;
    switchC CLOSED;
    nominal_voltage 7200;
    }

Capacitor Parameters

Properties

capacitor objects are derived from node objects, so any parameters of the node object are available as well.

The I/O column indicates whether a property is user-settable input (I), simulation-computed output (O), or both (IO).

Table 1: capacitor table 1
Property Name	Type	Unit	I/O	Description
pt_phase	set	N/A	I	Determines the participating phases. These are the phases the various control schemes will monitor to determine their actions. Follows the same conventions as the overall `phases` property in powerflow. Valid values: `A`, `B`, `C`, `D`, `N`.
phases_connected	set	N/A	I	Connection of the capacitors. This allows for delta-connected capacitors on a wye-connected system and vice versa. Follows the same conventions as the overall `phases` property. If left empty or undefined, defaults to the `phases` property of the capacitor. Valid values: `A`, `B`, `C`, `D`, `N`.
switchA	enumeration	N/A	IO	Status of the switch that enables or disables the capacitor attached to phase `A` if wye-connected or `AB` if delta-connected. Valid values: `OPEN`, `CLOSED`.
switchB	enumeration	N/A	IO	Status of the switch that enables or disables the capacitor attached to phase `B` if wye-connected or `BC` if delta-connected. Valid values: `OPEN`, `CLOSED`.
switchC	enumeration	N/A	IO	Status of the switch that enables or disables the capacitor attached to phase `C` if wye-connected or `CA` if delta-connected. Valid values: `OPEN`, `CLOSED`.
control	enumeration	N/A	I	Defines the control scheme the capacitor will utilize to perform switching operations. Valid control mode keywords are - `MANUAL` - Capacitor switching is controlled manually through `switchA`, `switchB`, and `switchC`. - `VAR` - VAR controlled mode. A remote line needs to be specified in `remote_sense` or `remote_sense_B` that will have its reactive power checked against `VAr_set_high` and `VAr_set_low`. - `VOLT` - Voltage controlled mode. The capacitor node itself or a node specified by `remote_sense` or `remote_sense_B` has its voltage checked against `voltage_set_high` and `voltage_set_low`. - `VARVOLT` - Combination control scheme. Has two modes. If `voltage_set_low` is specified, performs control similar to `VOLT` first, and then `VAR` second. If `voltage_set_low` is unspecified or set to zero, operates in `VAR` mode primarily. However, `voltage_set_high` is monitored and will switch the capacitors off and lock them out if exceeded (voltage safety).
cap_A_switch_count	double	N/A	IO	Hold of the number of times the switch has changed (OPEN to CLOSED, CLOSED to OPEN) on phase `A` if wye-connected or `AB` if delta-connected.
cap_B_switch_count	double	N/A	IO	Hold of the number of times the switch has changed (OPEN to CLOSED, CLOSED to OPEN) on phase `B` if wye-connected or `BC` if delta-connected.
cap_C_switch_count	double	N/A	IO	Hold of the number of times the switch has changed (OPEN to CLOSED, CLOSED to OPEN) on phase `C` if wye-connected or `CA` if delta-connected.
voltage_set_high	double	V	IO	High setpoint for voltage-based capacitor switching operations. This setpoint will turn the capacitors off.
voltage_set_low	double	V	IO	Low setpoint for voltage-based capacitor switching operations. This setpoint will turn the capacitors on.
voltage_deadband_center	double	V	I	The voltage deadband center
voltage_deadband	double	V	I	The deadband between voltage_set_high and voltage_set_low
VAr_set_high	double	VAr	IO	High setpoint for VAr-based capacitor switching operations. This setpoint will turn the capacitors on.
VAr_set_low	double	VAr	IO	Low setpoint for VAr-based capacitor switching operations. This setpoint will turn the capacitors off.
VAr_deadband_center	double	VAr	I	The VAr deadband center
VAr_deadband	double	VAr	I	The deadband between VAr_set_high and VAr_set_low
current_set_low	double	A	IO	high current set point for current control mode (turn on)
current_set_high	double	A	IO	low current set point for current control mode (turn off)
current_deadband_center	double	A	I	The current deadband center
current_deadband	double	A	I	The deadband between current_set_high and current_set_low
capacitor_A	double	VAr	I	Capacitor size information for capacitor connected to phase `A` in a wye connection or on phase `AB` in a delta connection.
capacitor_B	double	VAr	I	Capacitor size information for capacitor connected to phase `B` in a wye connection or on phase `BC` in a delta connection.
capacitor_C	double	VAr	I	Capacitor size information for capacitor connected to phase `C` in a wye connection or on phase `CA` in a delta connection.
cap_nominal_voltage	double	V	I	Capacitor rated nominal voltage. Used for situations when `nominal_voltage` doesn't match the rated voltage or if a line-to-line voltage is specified when the capacitors are on a wye-connected system. If left blank, defaults to the `nominal_voltage` specified.
time_delay	double	s	I	Time delay before any capacitor switching operation takes place. Represents mechanical switching delays.
dwell_time	double	s	I	Time period a switching operation must be consistently requested before any switching operation is attempted. Serves as a transient filter or additional hysteresis to prevent transient events from causing excessive capacitor switching.
lockout_time	double	s	I	Time period a capacitor will lock out switching operations after `voltage_set_high` is exceeded in the `VARVOLT` control method.
remote_sense	object	N/A	I	Remote node or link object for `VOLT`, `VAR`, or `VARVOLT` control schemes. If a node object is specified, the remote voltage is read. If link object is specified, the reactive power is read.
remote_sense_B	object	N/A	I	Remote node or link object for `VOLT`, `VAR`, or `VARVOLT` control schemes. If a node object is specified, the remote voltage is read. If link object is specified, the reactive power is read. Under the `VARVOLT` control scheme, this must be the opposite of the type specified in `remote_sense`.
control_level	enumeration	N/A	I	Specifies how the switching action occurs for all phases of the capacitor. Valid keywords are - `BANK` - All capacitors are switched based on the control scheme and `pt_phase` property. - `INDIVIDUAL` - Capacitors are switched individually based on the control scheme and `pt_phase` property.

Capacitor State of Development

Capacitor is considered a well developed and validated model in terms of powerflow solutions, however, models may be developed to include more advanced features in the future. Additional configurations and controls may be included as needed.