See Also
The following classes of controls are available during the OPF solution. Note, individual classes of controls can be enabled/disabled for the entire case using the OPF Options and Results dialog and for particular areas using the OPF Area Records display. Also, all classes of controls have associated minimum/maximum limits which are always enforced.
Generator MW output and Fast Start commitment
The generator MW outputs are the major control for controlling the MW flow in the network and for minimizing the objective function. Only generators in areas or super areas that are on "OPF" control are eligible for control; otherwise the generator's MW output remains fixed at its initial value. Whether a particular generator is available for control also depends upon the status of its AGC and OPF MW Control fields. These fields are set on the OPF Generator Records display. For Fast Start Generators, it is also possible to use the startup and shutdown of these generators as a control. See OPF Options: Control Options for more details.
Phase shifting Transformer tap position
Phase shifting transformers are used primarily to control the flow of real power in the network. When phase shifting transformers are controlled in the OPF routine, the phase angle is allowed to move anywhere within the phase angle range of the device in order to help alleviate violations on other branches in the system. The flow on the phase shifter is allowed to violate the prescribed MW range given for the phase shifter, but is NOT allowed to violate the MVA rating of the device.
Additionally, in order for a phase shifter to be included in the OPF solution dispatch, the XF Phase property of the area must be set to YES. Each individual phase shifter also has a property for being included in the OPF control that must be turned on in order for the phase shifter to participate in the OPF dispatch. This option can be set for a phase shifting transformer by opening its Information Dialog and checking the OPF Phase Shifter Control options on the OPF page of the dialog.
D-FACTS devices are primarily real power flow controls that work by changing the effective line impedance. The Xinj values of D-FACTS can be included as controls for dispatch during an OPF solution. The concept of controlling D-FACTS devices in the OPF is very similar to controlling a phase shifting transformer. See D-FACTS Control .
Load MW Dispatch
The load MW demands can also be included as controls for re-dispatch during an OPF solution. The concept of controlling a load is generally the same as controlling a generator. Loads can be assigned piecewise linear benefit curves, and included in the OPF dispatch algorithm. Only areas whose AGC control is set to "OPF" are eligible for control. Furthermore, the OPF area’s Load MW Dispatch property must also be set to YES. Each area load that is to be included for OPF dispatch must have a benefit model defined, and have its Available for AGC field set to YES. These fields can be set in the OPF Load Records display.
DC Line MW setpoint
DC Line MW setpoints can be used as controls in the OPF. See OPF DC Lines Records.
Island Slack Bus Angles
When enforcing bus angle constraints, island slack bus angles are automatically included as control variables. These controls have no associated cost, so moving these instead of other control variables is often the least costly solution to bring bus angles within tolerance. When the island slack bus angle is changed, all bus angles in the same island are moved by the same amount. There is no user option that will allow disabling or enabling island slack bus angles as controls. The island slack bus angle control will be added for each island that contains a bus that is enforcing its angle.