Connection

Note

This section of the documentation is auto-generated from the code of the Julia-based core model. Refer to IESopt.jl for any further details (which may require some familiarity with Julia).

If you spot incorrect math-mode rendering, or similar issues, please file an issue, since rendering documentation from Julia to Python is not the easiest task.

Overview

A Connection is used to model arbitrary flows of energy between Nodes. It allows for limits, costs, delays, …

Parameters

`node_from`

This Connection models a flow from node_from to node_to (both are Nodes).

mandatory: yes
default: \(-\)
values: string
unit: -

`node_to`

This Connection models a flow from node_from to node_to (both are Nodes).

mandatory: yes
default: \(-\)
values: string
unit: -

`carrier`

Carrier of this Connection. If not given, automatically picks the carrier of the Nodes it connects. This parameter is not necessary, and only exists to allow for a more explicit definition.

mandatory: no
default: \(-\)
values: string
unit: -

`capacity`

The symmetric bound on this Connection’s flow. Results in lb = -capacity and ub = capacity. Must not be specified if lb, ub, or both are explicitly stated.

mandatory: no
default: \(+\infty\)
values: numeric, col@file, decision:value
unit: power

`lb`

Lower bound of this Connection’s flow.

mandatory: no
default: \(-\infty\)
values: numeric, col@file, decision:value
unit: power

`ub`

Upper bound of this Connection’s flow.

mandatory: no
default: \(+\infty\)
values: numeric, col@file, decision:value
unit: power

`cost`

Cost of every unit of energy flow over this connection that is added to the model’s objective function. Keep in mind that negative flows will induce negative costs, which can be used to model revenues. Further, a bidirectional Connection (if lb < 0, which is the default, or if capacity is used) with a positive cost will lead to negative costs for the reverse flow. If you do not want this, split the Connection into two separate ones, each being unidirectional (with lb: 0). Remember, that these can share the same “capacity” (which is then set asub), even when using decision:value or col@file as value.

mandatory: no
default: \(-\)
values: numeric
unit: monetary (per energy)

`loss`

Fractional loss when transferring energy. Per default, this loss occurs “at the destination”, which means that for a loss of 5%, set as loss: 0.05, and considering a Snapshot where the Connection has a flow value of 100, it will “extract” 100 from node_from and “inject” 95 into node_to. Since the flow variable is given as power, this would, e.g., translate to consuming 200 units of energy at node_from and injecting 190 units at node_to, if the Snapshot duration is 2 hours. Refer to loss_mode for more information on how to modify this behaviour.

mandatory: no
default: \(0\)
values: \in [0, 1]
unit: -

`loss_mode`

Configures where the fractional loss (set by loss) occurs. to means that the loss occurs at the destination, from means that the loss occurs at the source, and split means that the loss is split between source and destination. Not that for most cases to is the correct choice, as it is the most common behaviour - the other options, e.g., lead to the possibility of drawing at a higher power from the node_from than the capacity of the Connection “allows”.

mandatory: no
default: \(to\)
values: to, from, split
unit: -

`delay`

Delay between withdrawing energy from node_from and injecting it into node_to. This can be used to model, e.g., river flows, where the water takes some time to travel from one point to another (e.g., in a cascade of reservoirs). Note that this delay is always “cyclic” meaning if it extends over the modeling period, it will be “wrapped around”, starting again at the beginning of the period. Further, the flow is always withdrawn at Snapshot t and injected at t + delay.

mandatory: no
default: \(0\)
values: \in [0, \infty]
unit: hours

`build_priority`

Priority for the build order of components. Components with higher build_priority are built before. This can be useful for addons, that connect multiple components and rely on specific components being initialized before others.

mandatory: no
default: \(0\)
values: numeric
unit: -

Detailed reference

Expressions

`in`

How to access this expression?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").exp.in

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").exp.in

Full implementation and all details: connection/exp_in @ IESopt.jl

The construction of a Connection’s in/out expressions is directly done in _connection_var_flow!(...), the function that constructs the variable flow.

`out`

How to access this expression?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").exp.out

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").exp.out

Full implementation and all details: connection/exp_out @ IESopt.jl

The construction of a Connection’s in/out expressions is directly done in _connection_var_flow!(...), the function that constructs the variable flow.

`pf_flow`

How to access this expression?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").exp.pf_flow

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").exp.pf_flow

Full implementation and all details: connection/exp_pf_flow @ IESopt.jl

Construct the JuMP.AffExpr holding the PTDF based flow of this Connection.

This needs the global addon Powerflow with proper settings for mode, as well as properly configured power flow parameters for this Connection (pf_V, pf_I, pf_X, …).

Variables

`flow`

How to access this variable?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").var.flow

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").var.flow

Full implementation and all details: connection/var_flow @ IESopt.jl

Add the variable representing the flow of this connection to the model. This can be accessed via connection.var.flow[t].

Additionally, the flow gets “injected” at the Nodes that the connection is connecting, resulting in

\[\begin{split} \begin{aligned} & \text{connection.node}_{from}\text{.injection}_t = \text{connection.node}_{from}\text{.injection}_t - \text{flow}_t, \qquad \forall t \in T \\ & \text{connection.node}_{to}\text{.injection}_t = \text{connection.node}_{to}\text{.injection}_t + \text{flow}_t, \qquad \forall t \in T \end{aligned} \end{split}\]

For “PF controlled” Connections (ones that define the necessary power flow parameters), the flow variable may not be constructed (depending on specific power flow being used). The automatic result extraction will detect this and return the correct values either way. Accessing it manually can be done using connection.exp.pf_flow[t].

Constraints

`flow_bounds`

How to access this constraint?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").con.flow_bounds

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").con.flow_bounds

Full implementation and all details: connection/con_flow_bounds @ IESopt.jl

Add the constraint defining the bounds of the flow (related to connection) to connection.model.

Specifying capacity will lead to symmetric bounds (\(\text{lb} := -capacity\) and \(\text{ub} := capacity\)), while asymmetric bounds can be set by explicitly specifying lb and ub.

Note

Usage of etdf is currently not fully tested, and not documented.

Upper and lower bounds can be “infinite” (by not setting them) resulting in the respective constraints not being added, and the flow variable therefore being (partially) unconstrained. Depending on the configuration the flow is calculated differently:

if connection.etdf is set, it is based on an ETDF sum flow,

if connection.exp.pf_flow is available, it equals this

else it equal connection.var.flow

This flow is then constrained:

\[\begin{split} \begin{aligned} & \text{flow}_t \geq \text{lb}, \qquad \forall t \in T \\ & \text{flow}_t \leq \text{ub}, \qquad \forall t \in T \end{aligned} \end{split}\]

Constraint safety

The lower and upper bound constraint are subject to penalized slacks.

Objectives

`cost`

How to access this objective?

# Using Julia (`IESopt.jl`):
import IESopt

model = IESopt.run(...)  # assuming this is your model
IESopt.get_component(model, "your_connection").obj.cost

# Using Python (`iesopt`):
import iesopt

model = iesopt.run(...)  # assuming this is your model
model.get_component("your_connection").obj.cost

Full implementation and all details: connection/obj_cost @ IESopt.jl

Add the (potential) cost of this connection to the global objective function.

The connection.cost setting introduces a fixed cost of “transportation” to the flow of this Connection. It is based on the directed flow. This means that flows in the “opposite” direction will lead to negative costs:

\[ \sum_{t \in T} \text{flow}_t \cdot \text{cost}_t \cdot \omega_t \]

Here \(\omega_t\) is the weight of Snapshot t.

Costs for flows in both directions

If you need to apply a cost term to the absolute value of the flow, consider splitting the Connection into two different ones, in opposing directions, and including lb = 0.