See Also
The following classes of inequality constraints are enforced during the OPF solution.
Generator real power limits
Generator real power limits are enforced during the LP solution.
Generator reactive power limits
Generator reactive power limits are enforced during the power flow solution.
Interface MW limits
Interface MW limits are enforced during the LP solution. In short, interface records are used to represent the aggregate flow through a number of different devices (see Interface Records for details). During the LP the MW flow through the interface is constrained to be less than or equal to a user specified percentage of its limit, provided the interface is active for enforcement. For an interface to be active for enforcement the following three conditions must be met:
- Interface enforcement must not be disabled for the case. This field can be set from either the OPF Options and Results dialog or the OPF Interface Records display. The default is that case interface enforcement is not disabled. Also note that interface flow is limited to a percent of its limit as specified by the interface's Limit Monitoring Settings.
- Interface enforcement must be active for at least one of the interface's areas. Note, an interface is assumed to be in each area that contains at least one of its components. This field can be set from the OPF Area Records display. The default is that interface enforcement is not active.
- Enforcement must be active for each individual interface. This field can be set from the OPF Interface Records display or in the Limit Monitoring Settings Dialog. The default is active.
Each interface that is active for enforcement is modeled as an inequality constraint, which may be either binding or not binding. If the constraint is not binding then it does not impact the solution. If a constraint is binding then it has an associated marginal cost of enforcement, which is shown on the OPF Interface Records display.
Transmission Line and Transformer (Branch) MVA Limits
Transmission line and transformer (branch) MVA limits are enforced during the LP solution. During the LP the branch line flow is constrained to be less than or equal to a user specified percentage of its limit, provided the branch is active for enforcement. For a branch to be active for enforcement the following three conditions must be met:
- Line/Transformer enforcement must not be disabled for the case. This field can be set from either the OPF Options and Results dialog or the OPF Line/Transformer Records display. The default is that case line/transformer enforcement is not disabled. Also note that the branch flow is limited to a percent of its limit as specified by the branche's Limit Monitoring Settings.
- Branch enforcement must be active for the branch's area. For tie-lines enforcement must be active for either area. This field can be set from the OPF Area Records display. The default is that branch enforcement is not active.
- Enforcement must be active for each individual branch. This field can be set from the OPF Line/Transformer Records display or in the Limit Monitoring Settings Dialog. The default is active.
Each branch that is active for enforcement is modeled as an inequality constraint, which may be either binding or not binding. If the constraint is not binding then it does not impact the solution. If a constraint is binding then it has an associated marginal cost of enforcement, which is shown on the OPF Line/Transformer Records display.
Bus Angle
Specified bus angle values can be enforced during the LP solution. During the solution, the angle is constrained to be within a specified tolerance of this specified angle, provided the bus angle is active for enforcement. For a bus angle to be enforced, the following three conditions must be met:
- Bus angle enforcement must not be disabled for the case. This field can be set from the OPF Options and Results dialog. The default is that the case bus angle enforcement is disabled.
- Bus angle enforcement must be active for the bus' area. This field can be set from the OPF Area Records display. The default is that bus angle enforcement is not activefor an area.
- Enforcement must be active for each individual bus. This is done by setting the Angle Tolerance to a large enough value. This field can be set from the OPF Bus Records display. The default is the angles are not enforced.