Constraint Table

Energy Min

Aurora honors a minimum MWh generation level across the month or year.

Energy Max

Specifies an annual/monthly limit in megawatt hours (MWh) of the total energy resources that Aurora can produce in the constraint set.

Energy CF Min

Aurora puts a floor on the resource capacity factor (CF) over the year. This constraint is equal to using an Energy Min constraint, but it lets you express it by capacity factor (CF) instead of MWh.

Energy CF Max

Aurora limits the resource's yearly capacity factor (CF). This constraint is equal to limiting the actual energy, but it allows you to express the constraint by capacity factor (CF) instead of MWh.

LT Capacity Min

Aurora constrains the build decisions so that the total average nameplate capacity from the online resources in the constraint is greater than or equal to the input target.

The Limit Type must equal Year, Year Cumulative, or Study for this constraint type.  

• With Limit Type = Year - Aurora adds a constraint for each year of the study putting a minimum on the total resource capacity with a begin year equal to that year.  

• With Limit Type = Year Cumulative - Aurora adds a constraint for each year of the study, limiting the total resource capacity online in that year (whether the begin year is in that year or the year before). 

• With Limit Type = Study - Aurora adds one single constraint for the whole study horizon, limiting the total average nameplate capacity online across all years.  

Note that Traditional LT Method is not allowed with this option.  If selected, Aurora uses a Mixed Integer Program instead.

LT Capacity Max

Aurora constrains the build decisions so the total average nameplate capacity from online resources in the constraint is less than or equal to the input target.

The Limit Type must equal Year, Year Cumulative, or Study for this constraint type.  

• With Limit Type = Year, Aurora adds a constraint limiting the total resource capacity for each year of the study, with a beginning year equal to that year. 

• With Limit Type = Year Cumulative - Aurora adds a constraint for each year of the study, limiting the total resource capacity online in that year (whether its begin year is that year or the year before).  

• With Limit Type = Study - Aurora adds one constraint for the whole study horizon, limiting the total average nameplate capacity online across all years.  

Note that Traditional LT Method is not allowed with this option. If selected, Aurora uses a Mixed Integer Program (MIP) instead.

LT Energy Min

Aurora will  honor the min constraint in the LT decisions,  not the dispatch. It ensures that enough energy is available from the resources built to meet the target, if possible.

This is particularly useful in modeling RPS build targets. Note that the Limit Type must equal the Year for this constraint type.

LT Energy Max

Aurora will honor the constraint in the LT decisions, not the dispatch. It limits the builds so that the expected energy from the online resources in the constraint is less than the input target each year.

Note that the Limit Type must equal the Year for this constraint type.

LT Reserve Margin Min

LT Reserve Margin Max

Aurora will accept additional reserve margin target constraints, including monthly. You can only reference this constraint by zones directly in the Constraint ID column of the Zone Definition table. Aurora uses  all zone sets to reference the constraint as the region where Aurora meets the reserve margin target.  

Enter the Limit Value as a percent, just like it is for the pools and zones (e.g., for LT Reserve Margin Min, 15 means that Peak Capacity/Peak Demand needs to be at least 1.15). Aurora will sum up any Firm Imports/Firm Exports across the zones that are within the constraint.  

For this constraint, Aurora uses all resources in the defined zones and the total demand of all zones to determine the reserve margin values. To put a reserve margin constraint on every month,  set the Limit Type = Month (and the Limit column can take a time series input).

To put an annual constraint that only looks at certain months in the year, use the Limit Definition column in conjunction with Limit Type = Year.  

For example, specify a reserve margin target of 15% for all summer months and a second target of 15% for all winter months to ensure coverage of both winter and summer peaks.

Emission(e.g., tons, tonnes)

Emission Rate(e.g., tons/ MWh)

Enter emission limits for a given Set ID and emission type so multiple rows with the same Set ID may exist.

For example, limit each of the three emission types by entering three rows in the Constraint table for carbon dioxide (CO2), sulfur dioxide (SO2), and oxides of nitrogen (NOx).

The Item ID should match a value in the Name column of the Emission Rate table. Aurora collects the rows into the same constraint set by entering a common Set ID value for all three rows. 

Specify the emission production cost in the Emission Pricing column of the Constraint table. The table may reference a supply curve (see column description for more details).

Any resources referencing an emission constraint in the Constraint table will override the resource-level emission prices with the emission price for the constraint. Resource emissions and energy can be limited by referring to the relevant constraint set(s).

Enter the relevant Set ID value from the Constraint table in the Constraint ID column in three different ways:

• Resources, New Resources, Link or RMT tables - individual resources can be associated with a constraint set

 NOTE: Pumped storage and demand curtailment units are not allowed.

• Resource Groups table - all resources in a resource group can be collectively associated with a constraint set

• Zone Definition table - all resources in a zone can be collectively associated with a constraint set

The Constraint ID column in these three tables may contain multiple constraint set references by entering several Set ID values separated by commas. Thus, resources may simultaneously participate in many constraint sets.

When using one of the Mixed-Integer Program (MIP) Methods with annual emission targets specified in the Constraint table, Aurora adds explicit constraints in the LT solution to limit the builds of emitting units that contribute to the constraint.

Fuel Min

Fuel Max

Aurora puts a minimum limit on the total fuel usage of all fuels by referencing the Set ID in the Fuel Constraint ID column of the Fuels table.

All resources using this fuel directly or indirectly (via a Reference Fuel) participate in the constraint, and Aurora will properly distinguish between primary and secondary fuel types.

Fuel type constraints cannot be referenced directly by resources.

Link Flow Max

Link Flow Min

Aurora limits the total flow, in MWh, across a set of Zonal Links.

Define the links in the constraint in two ways:

• Net Import Zones = a comma-delimited list of zones. The constraint will limit the net import into that set of zones.

• Constraint ID column in the Link table = Set ID.  For each link that references the constraint set, Aurora will limit the directional flow on all specific links included.