Optimal Power Flow
The DIgSILENT PowerFactory Optimal Power Flow (OPF) serves as the ideal complement to the existing load flow functions. Whereas the standard load flow calculates branch flows and bus bar voltages based on specified "set points" (active/reactive power generation, generator voltage, transformer tap positions, etc.) the OPF also calculates the "best possible" values for "higher level set points" considering a user specified objective function and a number of constraints. In this way, the OPF adds intelligence and consequently improves efficiency and throughput of power system studies significantly. The OPF avoids the tedious and manual search for a "best possible solution" via several, iterative runs requiring a number of manual modifications, which quite often are leading to un-comparable solutions when performing various load flow sequences to arrive at certain conditions as defined by various load flow scenarios. From practically any starting point, within a couple of fast iterations, the OPF will assure a globally optimal and reproducible solution, satisfying the defined system limits while minimizing the applied cost functions.
From point of view of software application, the OPF is just an enhanced function of the standard load flow, being fully integrated, powerful and easy-to-use. The OPF is simply accessed via an extra page of the load flow option definitions.
The OPF supports a number of new applications typically found in today’s less-regulated power markets such as:
- Scheduling of Ancillary Services for reactive power and active power
- Development of system reference scenarios
- Transfer capability analysis
- Determination of voltage stability limits
- Implicit Penalty Function consideration
- Comparative reliability analysis studies
Supported objective functions:
- Minimize system losses
- Minimize fuel costs (based on non-linear fuel cost functions for each generator)
- Maximize profit (considering fuel costs and load tariffs)
- Minimize area exchange flows.
Above listed objective functions are solved under the consideration of a number of possible constraints to which the final solution must comply with are:
- Branch flow limits (loading)
- Bus bar voltage limits
- Generator reactive power and stator current limits
- Generator active power and reserve limits
- Transformer tap changer limits
- Adjustable shunt limits
Because the OPF can also dispatch the active power of generators considering reserve limits and the fuel cost minimization which is based on non-linear fuel cost functions, the PowerFactory OPF is at the same time very advanced Economic Dispatch function.