To represent the physical grid components, and the calculation results, this library uses a graph data model. In this document, the graph data model is presented with the list of all components types, and their relevant input/output attributes.
Component Type Hierarchy and Graph Data Model
The components types are organized in an inheritance-like hierarchy. A sub-type has all the attributes from its parent type. The hierarchy of the component types is shown below.
Note
The type names in the hierarchy are exactly the same as the component type names in
the power_grid_model.power_grid_meta_data
, see Native Data Interface
This library uses a graph data model with three generic component types: node
, branch
, branch3
and appliance
. A
node is similar to a vertex in the graph, a branch is similar to an edge in the graph and a branch3 connects three nodes
together. An appliance is a component which is connected (coupled) to a node, it is seen as a user of this node.
The figure below shows a simple example:
node_1 ---line_3 (branch)--- node_2 --------------three_winding_transformer_8 (branch3)------ node_6
| | |
source_5 (appliance) sym_load_4 (appliance) node_7
There are four nodes (points/vertices) in the graph of this simple grid.
The
node_1
andnode_2
are connected byline_3
which is a branch (edge).The
node_2
,node_6
, andnode_7
are connected bythree_winding_transformer_8
which is a branch3.There are two appliances in the grid. The
source_5
is coupled tonode_1
and thesym_load_4
is coupled tonode_2
.
Symmetry of Components and Calculation
It should be emphasized that the symmetry of components and calculation are two independent concepts in the model. For
example, a power grid model can consist of both sym_load
and asym_load
. They are symmetric or asymmetric load
components. On the other hand, the same model can execute symmetric or asymmetric calculations.
In case of symmetric calculation, the
asym_load
will be treated as a symmetric load by averaging the specified power through three phases.In case of asymmetric calculation, the
sym_load
will be treated as an asymmetric load by dividing the total specified power equally into three phases.
Reference Direction
The sign of active/reactive power of the Appliance and Sensor depends on the reference direction.
For load reference direction, positive active power means the power flows from the node to the appliance/sensor.
For generator reference direction, positive active power means the power flows from the appliance/sensor to the node .