Knowledge Base

Assigning Costs to Control Adjustments in OPF

Download the example files.

Simulator’s Optimal Power Flow (OPF) has 2 options for objective functions: Minimum Cost or Minimum Control Change. Generally Minimum Cost is used where generator bids or costs and load benefits are known. Minimum Control Change is used where it is desirable to relieve transmission overloads with minimum deviation from the present state. The Minimum Control Change objective function assigns a “cost” of moving a control a fixed amount, which is the same for every controllable generator or load.

In some cases, it may be desirable to assign different costs to different controls. For example, perhaps curtailing a load by 1 MW should cost 10 times more than adjusting a generator output by 1 MW. This can be done in PowerWorld Simulator by assigning piecewise linear generator cost models and piecewise linear load benefit models that have breakpoints at the present MW values.

Sample auxiliary files are provided here to initialize the nominal or desired load and generator values to their present values. Separate files are provided to initialize generator and load values. Load these into PowerWorld Simulator prior to running the OPF with Minimum Cost objective function. Re-load them whenever it is desired to re-set the nominal values to present values. Notes and detailed descriptions of the actions are included as comments in each file.

Tip: Add these to the “Quick Aux” menu if needed to reset nominal load and generation values repeatedly during analysis. (Tools Ribbon -> Script -> Quick Aux -> Define… -> Add)

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March 2, 2015