Substation

Substations were used to connect distribution powerflow in the powerflow module with PowerWorld through the network module. The substation object converts the sequence voltage provided by the network module to three-phase swing bus voltage for the unbalanced three-phase powerflow solution. The substation object also passes the unbalanced three-phase powerflow solution to back to the network module as an single power value representing the average load on all three phases of the swing bus. Furthermore, the substation object sets which phase is the reference phase for the distribution powerflow. A typical substation implementation is

object substation {
    name SubS;
    bustype SWING;
        parent network_node;
        reference_PHASE_A;
        phase ABCN;
    nominal_voltage 7199.558;
}

In order to properly connect the substation object to the network module, the substation object's parent must be a pw_load object.

Substation Parameters

Properties

substation 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: substation table 1

Property Name	Type	Unit	I/O	Description
zero_sequence_voltage	complex	V	IO	The zero sequence representation of the voltage for the substation object.
positive_sequence_voltage	complex	V	IO	The positive sequence voltage given from a PowerWorld bus model or a user specified value.
negative_sequence_voltage	complex	V	IO	The negative sequence representation of the voltage for the substation object.
base_power	double	VA	I	The 3 phase VA power rating of the substation.
power_convergence_value	double	VA	I	Default convergence criterion before power is posted to pw_load objects if connected, otherwise ignored
reference_phase	enumeration	N/A	I	The phase that will be used as the reference angle for the powerflow solution. - PHASE_A(Default) - PHASE_B - PHASE_C Valid values: PHASE_A, PHASE_B, PHASE_C.
transmission_level_constant_power_load	complex	VA	I	The positive-sequence constant power load to be posted directly to the pw_load object ([powerflow] solver does not handle this, it is explicitly converted and posted to PowerWorld's solver).
transmission_level_constant_current_load	complex	A	I	the positive-sequence constant current load to be posted directly to the pw_load object ([powerflow] solver does not handle this, it is explicitly converted and posted to PowerWorld's solver).
transmission_level_constant_impedance_load	complex	Ohm	I	The positive-sequence constant impedance load to be posted directly to the pw_load object ([powerflow] solver does not handle this, it is explicitly converted and posted to PowerWorld's solver).
distribution_load	complex	VA	O	The total load of all three phases at the substation object.
distribution_power_A	complex	VA	O	The measured power of the attached powerflow on phase A.
distribution_power_B	complex	VA	O	The measured power of the attached powerflow on phase B.
distribution_power_C	complex	VA	O	The measured power of the attached powerflow on phase C.
distribution_voltage_A	complex	V	O
distribution_voltage_B	complex	V	O
distribution_voltage_C	complex	V	O
distribution_voltage_AB	complex	V	I
distribution_voltage_BC	complex	V	I
distribution_voltage_CA	complex	V	I
distribution_current_A	complex	A	I
distribution_current_B	complex	A	I
distribution_current_C	complex	A	I
distribution_real_energy	double	Wh	O
measured_reactive	double	kVar	I

Substation State of Development

The only transmission powerflow software that substation currently works with is PowerWorld. Please note that the specific the transmission current and impedance loads are converted to complex power values first and then posted to the proper properties(load_current and load_impedance) in the pw_load object. The average_transmission_power_load value must be added to the average_distribution_load before posting to pw_load(load_power).

Substation's three phase voltages are determined differently dependent upon three scenarios. If there is a pw_load object attached to the substation object, then the three phase voltages are determined by the sequence voltage value read from the pw_load object. The three phase voltages are determined by the positive_sequence_voltage property if there is a player object populating that property in the absence of a pw_load object. In the absence of a player object and a pw_load object, the three phase voltages are determined by user input or the substation object's powerflow parent just like any node object. If there is no pw_load connected to the substation then the substation doesn't post the average_distribution_load, average_transmission_current_load, average_transmission_impedance_load, and average_transmission_power_load properties.