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Application concept

The transmission and distribution integration task is to develop the interaction path for GridLAB-D and a transmission-level solver, PowerWorld Simulator ("Simulator" in this document). This capability will allow better representation of the responses from distribution-level systems and an examination of their impact on the transmission-level grid. The framework will allow further investigations of using distribution-level devices as transmission-level resources, as well as the impact of demand response on the transmission power system.

Use Case

The transmission and distribution solver integration capability will be used to help validate an aggregate model of thermostatic loads in a local utility's area of operation. This aggregate model will be used to determine control actions for providing benefit to the grid. GridLAB-D will simulate representative feeders of this utility, while the PowerWorld Simulator will run a reduced WECC transmission model of that region, or one of the WECC transmission planning cases. The results of these simulations will validate the responses and impacts of the aggregate model, as well as the proposed control schemes.

General Requirements

The transmission and distribution solver integration will allow GridLAB-D and the PowerWorld Simulator to exchange relevant data and interact during a time-series analysis of static powerflow conditions. It will require the following capabilities:


The interface shall allow the exchange of relevant power system data needed by both solvers.


Values for current system voltage at the connection bus will be passed from Simulator to GridLAB-D.


Voltage values will be passed as three-phase, unbalanced voltage levels from Simulator to GridLAB-D, if supported.


If voltages can not be passed as three-phase, unbalanced, they will be converted to three-phase voltages appropriately for GridLAB-D.


Values for the appropriate load composition will be passed from GridLAB-D to Simulator.


If loads can be passed as unbalanced, individual three-phase components, they will be passed as such.


If only positive sequence data transfers are available, loads should be aggregated to the appropriate representation.


If loads are only modeled as a specific constant-power or constant-impedance type in Simulator, GridLAB-D will pass the load back as an appropriate model.


GridLAB-D and Simulation will coordinate timestep progression.


GridLAB-D will provide to Simulator indications of the time it would like to update and reiterate the model.


Simulator will provide to GridLAB-D indications of the time it will simulate toward next.


Simulator and GridLAB-D will negotiate the next valid timestep.


The interface shall only be required to be functional under the Microsoft Windows operating environment as the PowerWorld Simulator only operates under Microsoft Windows.


The interface shall facilitate read access to the PowerWorld model for monitoring and recording purposes.


The interface shall allow access to any object, regardless of class, in the PowerWorld model.


The interface shall allow access to any public property of a specified object in PowerWorld, regardless of data type.

See also