Optimal Power Flow
The PowerFactory Optimal Power Flow (OPF) serves as the ideal complement to the existing load flow functions. Where the standard load flow calculates branch flows and busbar 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 optimizing a user-specified objective function and a number of user-defined constraints. In this way, the OPF adds intelligence and consequently improves efficiency and throughput of power system studies significantly.
Building on the load flow calculation, PowerFactory offers two calculation methods:
- AC optimization based on a state-of-the-art interior-point algorithm
- DC optimization based on linear programming using simplex methods, also supporting contingency constrained optimization.
OPF in PowerFactory allows easy configuration of the optimization task via the simple selection of an objective function, controls (i.e. system variables to be optimized), and constraints. The optimal solution for the selected objective function is calculated under the consideration of a number of possible constraints with which the final solution must comply. All controls and constraints can be flexibly-defined on a component level.
AC Optimization
Supported Objective Functions:
- Minimization of system losses
- Minimization of costs (based on arbitrary (non-linear) cost curves for generators and load tariffs for external grids)
- Minimization of load shedding
Control Variables:
- Generator active power dispatch
- Generator reactive power dispatch
- Transformer tap positions
- Switchable shunts
- Load consumption (for optimal load shedding)
Supported Constraints:
- Branch flow limits (loading)
- Voltage limits (min/max) for busbars/terminals
- Active power limits of generators
- Reactive power limits of generators
- Transformer tap changer limits
- Adjustable shunt limits
- Boundary flow limits (min/max limits for active and reactive power flow along any user-definable boundary)
Since the OPF can dispatch the active power of generators considering reserve limits and considering fuel cost minimization (which is based on non-linear fuel cost functions), the PowerFactory OPF is also a highly advanced economic dispatch function.
DC Optimization
The DC Optimization builds on a sensitivity-based linear programming approach. Most notably, it allows a contingency constrained optimization to be carried out for any predefined list of contingency cases. The optimization simultaneously considers all contingency cases, and the solution is globally optimal and guaranteed to be feasible over all contingency cases (i.e. not violating any constraints in any of the contingencies).
Supported Objective Functions:
- Feasibility check
- Minimization of costs (based on arbitrary (non-linear) cost curves for generators and load tariffs for external grids)
- Minimization of generator dispatch change, i.e. finding a feasible solution with minimal re-dispatching
- Minimization of pre- to post-fault generator dispatch change (available for contingency constrained optimization only), i.e. finding optimal dispatch for the base case and each contingency case such that the change between the base case and each contingency case is minimal
- Minimization of pre- to post-fault transformer tap change (available for contingency constrained optimization only), i.e. finding optimal transformer tap settings for the base case and each contingency case such that the change between the base case and each contingency case is minimal
Control Variables:
- Generator active power dispatch - for base case and all contingency cases
- Transformer tap positions - for base case and all contingency cases
- Load consumption
Supported Constraints:
- Branch flow limits (loading) – for base case and all contingency cases
- Active power limits of generators – for base case and all contingency cases
- Transformer tap changer limits – for base case and all contingency cases
- Boundary flow limits (min/max limits for active and reactive power flow along any user-definable boundary) – for base case and all contingency cases
- Maximum number of tap changes per contingency
