NEPLAN | N-1 Constrained Optimal Power Flow (LMPs)

back to overview

Optimal Power Flow (OPF) module calculates the control variable settings and the network state (complex variables, line currents) that optimize the objective set by the user. Objective is usually the minimization of the active power losses or the minimization of the total generation costs. OPF can be extended to the Contingency Constrained OPF (CC-OPF) that ensures N-1 system operating security. CC-OPf delivers a network state that is optimal in terms of a user-defined objective, satisfies all operating and control constraints and additionally satisfies all the network power balance equations for every single element or node failure.

General Characteristics

  • Control variables: active / reactive power generation, schedule voltages of generators and taps of ULTC-transformers, reference values of HVDC systems and FACTS (UPFC, STATCOM, SVC, TCSC)
  • Variable limits for bus voltages, branch loadings, active and reactive power of generators
  • Individual or general limits, ’consider/not consider’ limits function
  • Objective function: apply to whole network / to a certain area or zone, minimize / maximize MW losses, Mvar losses, generation cost, MW import or Mvar import, MW Interface flow
  • Multi-objective function is possible (use of weighting factors)
  • Security constrained optimization (with N-1 contingency constraints)


Upon calculation results are automatically displayed on the single line diagram while their content and graphical information can be customized. Result evaluation and processing is easier due to visualization functions:

  • Optimization results: binding constraints, variables at limits, lambda multipliers, sensitivities, network controls, colouring of limiting network elements in the graphic
  • Overloaded elements or nodes with voltages outside predefined limits are highlighted
  • Line thickness corresponds to element loading
  • Results can be saved in a text file (ASCII)
  • Table output: for the whole network, individually for each area / zone. Listing of power flows between area/zones, overloaded elements, sorting function, selective output
  • Table interface with MS-Excel