Volt Var Control

With multiple feeders attached to a common point, it is often useful to coordinate the voltage regulators and capacitors on the system. The volt_var_control object coordinates selected regulator and capacitor objects on the system. Using voltage measurements at node object points, the volt_var_control tries to maintain a desired voltage. In addition to voltage measurements, the volt_var_control utilizes a power measurement at a link object to determine how to switch various capacitor objects on the system in and out of service. Due to differences in the timing of power calculations in the Forward-Back Sweep and Newton-Raphson powerflow solvers, capacitors may switch at slightly different intervals for the same system. The overall control behaves the same in both solver methods, but this difference in capacitor timing may result in different final operating points. A typical Volt-VAr Controller implementation is

object volt_var_control {
    name IVVC37;
    control_method ACTIVE;
    capacitor_delay 10.0;
    regulator_delay 5.0;
    desired_pf 0.98;
    d_max 0.8;
    d_min 0.1;
    substation_link "SubTransNode-799";
    regulator_list "reg799-781,regnode799-U0081";
    capacitor_list "CapNode_A,CapNode_B";
    voltage_measurements "load829,1,load841,1,load825,1,U0029,2,U0041,2,U0025,2";
    minimum_voltages 2500.0;
    maximum_voltages 3000.0;
    desired_voltages 2600.0;
}

Many of the parameters on the Volt-VAr Controller can be left unspecified. When unspecified, default values or criteria are enacted. A minimalist implemenation would look similar to

object volt_var_control {
    name IVVC37;
    regulator_list "reg799-781,regnode799-U0081";
    capacitor_list "CapNode_A,CapNode_B";
}

Volt Var Control Parameters

Properties

volt_var_control does not declare inherited parent classes.

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

Table 1: volt_var_control table 1
Property Name	Type	Unit	I/O	Description
control_method	enumeration	N/A	I	Defines the control scheme the volt_var_control object is currently operating in. There are two modes currently supported: - `STANDBY` - The volt_var_control is inactive and all regulator and capacitor control is handled by their local definitions. - `ACTIVE` - The volt_var_control is actively adjusting the regulators of interest, as well as coordinating capacitor insertions and removals. This is the default state.
capacitor_delay	double	s	I	Default delay for any capacitors under the volt_var_control object's control. If a delay is not explicitly defined in the capacitor's local properties, this value will be used as the time delay for all switching operations. Defaults to 5.0 seconds.
regulator_delay	double	s	I	Default delay for any regulators under the volt_var_control object's control. If a delay is not explicityly defined in the regulator_configuration object association with the regulator, this value will be used as the time delay in all tap-changing operations. Defaults to 5.0 seconds.
desired_pf	double	N/A	I	The value for desired_pf is used for setting threshold value for switching capacitors in and out of the system. It is determined at the `substation_link` object. If `pf_signed` is set to true, a negative value represents an inductive power factor (lagging) desired and a positive value represents a capacitive power factor (leading). Defaults to 0.98.
d_max	double	N/A	I	Scaling constant for switching the capacitors on as a ratio of their size to the required reactive power correction. Typically between 0.3 and 0.6. It must not overlap with `d_min`, and a larger spread between the two values helps prevent capacitor switching oscillations. Defaults to 0.6.
d_min	double	N/A	I	Scaling constant for switching the capacitors off as a ratio of their size and the required reactive power correction. Typically between 0.1 and 0.4. It must not overlap with `d_max`. As with `d_max`, a larger spread between `d_min` and `d_max` will help prevent capacitor switching oscillations. Defaults to 0.3.
substation_link	object	N/A	I	Defines the link to extract power information from for power factor correction. This object must be of the main-type link. Typically, this will be attached to a subtransmission-level transformer object to monitor reactive power for the entire network. If unpopulated, this defaults to monitoring the power through the first regulator specified in `regulator_list`.
pf_phase	set	N/A	I	Defines the phases of `substation_link` to monitor and accumulate for the power factor calculations. `pf_phase` can be any combination of `PHASE_A`, `PHASE_B`, or `PHASE_C`. If left blank, `pf_phase` will default to the phases of the `substation_link` object. Valid values: `A`, `B`, `C`.
regulator_list	char1024	N/A	I	List of regulators for the volt_var_control object to control. The list is a comma-separated object name for each regulator for which control is desired. No trailing comma is required. One regulator would be specified as `regulator_list reg799781;`, while three would be `regulator_list reg799781,reg981,reg01;`.
capacitor_list	char1024	N/A	I	List of capacitors for the volt_var_control object to control. This list is also comma-separated, like the `regulator_list`. If no capacitors are specified, no reactive adjustments are performed. All capacitors are operated in banked mode by the volt_var_control object. The listed capacitors are sorted by size and distance for switching operations. An example capacitor list is `capacitor_list CapA,CapB,CapC`.
voltage_measurements	char1024	N/A	I	List of end-of-line measurements for the volt_var_control to use in regulator control. This list is comma-separated, like the `capacitor_list` and `regulator_list`. If left blank, the measurement point defaults to load side of each regulator in `regulator_list`. The list can take two formats, depending on the number of regulators: - One regulator - The list is a comma-separated list of just the object names. No regulator designation is necessary, since only one regulator is present. An example is br/> - `measurement_list NodeA,NodeB,NodeC,NodeD;`. - One or more regulators - The list is a comma-separated list of object names, and their associated regulator. All measurements must be represented as a pair in the list. The first item is the object name, and the second item is the regulator position in the `regulator_list` variable. For example, `measurement_list NodeA,1,NodeC,2,NodeB,1;` will assign `NodeA` and `NodeB` to regulator 1, and `NodeC` to regulator 2. Notice these can occur in any regulator order, as long as the second portion of the data pair is the regulator number.
minimum_voltages	char1024	N/A	I	List of minimum voltages for the volt_var_control object to maintain. If only 1 value is specified, this value will be used for all regulators in `regulator_list`. A value can be specified for each regulator as a comma-separated list. For example, to specify two minimum voltage levels for two different regulators, use `minimum_voltages 2600,2500;`. If left blank, the minimimum voltage is set at 0.95 p.u. of the regulator's TO node `nominal_voltage`.
maximum_voltages	char1024	N/A	I	List of maximum voltages for the volt_var_control object to maintain. If only 1 value is specified, this value will be used for all regulators in `regulator_list`. A value can be specified for each regulator as a comma-separated list. For example, to specify two maximum voltage levels for two different regulators, use `maximum_voltages 4500,4400;`. If left blank, the maximimum voltage is set at 1.05 p.u. of the regulator's TO node `nominal_voltage`.
desired_voltages	char1024	N/A	I	List of desired, or target voltages for the volt_var_control object to maintain. If only 1 value is specified, this value will be used for all regulators in `regulator_list`. A value can be specified for each regulator as a comma-separated list. For example, to specify two desired voltage levels for two different regulators, use `desired_voltages 4500,4400;`. If left blank, the desired voltage is set at the regulator's TO node `nominal_voltage`.
max_vdrop	char1024	N/A	I	List of voltage drop thresholds for high or low loading operation (selection of `high_load_deadband` or `low_load_deadband` for a regulator). If the voltage drop between the regulator and the lowest end-of-line measurement is greater than `max_vdrop`, the corresponding `high_load_deadband` is used. Otherwise, the corresponding `low_load_deadband` is used. `max_vdrop` can be a comma-separated list of values for each regulator of `regulator_list`. if only one value is specified, that value will be used for all regulators. If left blank, `max_vdrop` defaults to 1.5x the corresponding regulator object's step up tap voltage value.
high_load_deadband	char1024	N/A	I	List of tap-changing bandwidth thresholds for high loading operation (as determined by `max_vdrop`). `high_load_deadband` represents a +/- `high_load_deadband` deadband around the desired voltage before a tap change is requested on the regulator. This can be specified for each regulator as a comma-separated list. If a single value is specified, that value will be used on all regulators in the `regulator_list`. If unspecified, `high_load_deadband` defaults to the voltage value associated with a single tap change on the regulator.
low_load_deadband	char1024	N/A	I	List of tap-changing bandwidth thresholds for low loading operation (as determined by `max_vdrop`). `low_load_deadband` represents a +/- `low_load_deadband` deadband around the desired voltage before a tap change is requested on the regulator. This can be specified for each regulator as a comma-separated list. If a single value is specified, that value will be used on all regulators in the `regulator_list`. If unspecified, `low_load_deadband` defaults to the voltage value associated with a two tap change on the regulator (2x the default of `high_load_deadband`).
pf_signed	bool	N/A	I	Set to true to consider the sign on the power factor. Otherwise, it just maintains the deadband of +/-desired_pf

VoltVar Control State of Development

VoltVar Control is considered a well developed model, but has not been fully validated at this time. Advanced features and additional controls may be added as needed.