OptGen · Transmission expansion
OptNet
OptGen's transmission network expansion module
OptNet is the network module of OptGen, PSR's expansion planning model, fully integrated into the SDDP platform. Given an existing network and a list of candidate circuits, OptNet determines the minimum-cost set of reinforcements that ensures secure operation across all the dispatch scenarios considered, with no circuit overloads or load shedding, and can also enforce N-1 contingency criteria.
Modeling capabilities
OptNet represents the transmission network with a linearized active power flow, formulated as a mixed-integer linear program (MIP). This representation gives a good approximation of power flows in meshed high-voltage networks, avoids the convergence problems of nonlinear power flows when the network is not yet reinforced, naturally accommodates islanded buses, and can be solved with commercial MIP solvers. All generation and network data are taken directly from the SDDP database.
- AC buses, with active power generation, load, and power injections
- Transmission lines and transformers, characterized by their reactance and capacity
- DC buses, DC links, and AC/DC converters
- Series capacitors
- Flow controllers and phase-shifting transformers
- Active power losses, through an optional piecewise linear approximation
- Sum-of-circuit-flow constraints, which can represent additional operating limits such as voltage stability
- N-1 circuit contingencies, checked against emergency circuit ratings
Candidate circuits (lines, transformers, DC links, series capacitors, and flow controllers) are configured as projects in the OptGen screens, where their investment costs and constraints are defined in the same way as generation candidates.
Transmission expansion problem
OptNet minimizes the annualized investment cost of the selected candidate circuits plus a high penalty on any remaining network violations.
Load shedding
The minimum total unsupplied load required to keep the network within its limits.
Circuit loading
The total overload (loading slack) in the monitored circuits.
Robust expansion plans
The network constraints are replicated for every dispatch scenario, so the resulting expansion plan is robust: operating limits are met in all of them.
Tolerance to minor congestion
To avoid investments triggered by minor congestion, the user can also accept small deviations from the SDDP dispatch.
Solution algorithm
OptNet offers three complementary solution methods.
Decomposition
Finds the optimal expansion plan: a greedy heuristic first delivers a feasible plan, and Benders decomposition then converges to the optimal solution.
Heuristic
Runs only the greedy heuristic, delivering a fast feasible plan for a first-pass analysis or as a starting point for the Decomposition method.
Redundancy analysis
Starts from a given expansion plan and identifies, in decreasing order of investment cost, the circuits that can be removed without compromising network feasibility.
SDDP integration
As part of OptGen, OptNet plans the transmission side of the hierarchical generation and transmission (G&T) expansion planning workflow of the SDDP platform. Because all models live on the same platform, OptNet reads the SDDP data and results directly from the shared database.
OptGen
SDDP
OptNet
SDDP
NetPlan
OptGen first decides the expansion of generation and/or of the interconnections among regions. SDDP then computes the optimal hydrothermal dispatch, which defines the dispatch scenarios: combinations of stages, scenarios, and load blocks, typical days, or hours. OptNet, OptGen's network module, uses these scenarios to decide the minimum-cost transmission reinforcements, and SDDP is finally run again with the complete G&T plan to obtain the final operating cost and dispatch under the reinforced network.
Before an integrated G&T study
Run OptNet first to prune the candidate circuit list.
After an OptGen integrated G&T run
Run OptNet afterwards to complement the transmission plan and remove any residual overloads or load shedding.
Once the active power plan is defined, NetPlan AC OPF can assess the reactive power and voltage requirements of the reinforced network.
Explore NetPlanResults
Each OptNet run produces:
A PSRIO dashboard
Summarizing the main results of the expansion analysis, such as the selected candidate circuits, the resulting investment cost, and the network performance.
Detailed reports
A set of detailed reports describing the resulting expansion plan and the performance of the network.
A complete set of output files
Available in the Output selection screen of the SDDP platform for further analysis, customized charts, and PSRIO dashboards.
- Selected candidate circuits and their commissioning dates
- Investment cost of the expansion plan
- Generation deviations from the SDDP dispatch, when enabled
- Remaining overloads, used to refine the candidate list
- And much more
Try OptNet now
Need support?
As an active user of PSR solutions, you have access to our support services and our Knowledge Hub, a platform where you can find documentation, frequently asked questions, and detailed methodologies.