scopflow.md

Security-constrained optimal power flow (SCOPFLOW)

SCOPFLOW solves a contingency-constrained optimal power flow problem. The problem is set up as a two-stage optimization problem where the first-stage (base-case) represents the normal operation of the grid and the second-stage comprises of $`N_c`$ contingency scenarios. Compactly, the problem can be set up in the following form:

$$\begin{aligned} \text{min}&~\sum_{c \in \{0,N_c\}}f_c(x_c)& \\ &\text{s.t.}& \\ &~g_c(x_c) = 0~~~c \in \{0,N_c\}& \\ &~h_c(x_c) \le 0~~c \in \{0,N_c\}& \\ &x^- \le x_c \le x^+~~c\in \{0,N_c\}& \\ -\Delta{x}_c & \le x_c - x_0 \le \Delta{x}_c~~c \in \{1,N_c\}& \end{aligned}$$

where $`N_c`$ is the number of contingencies. The total number of scenarios equals $`N_c + 1`$, i.e., the base-case + $`N_c`$ contingencies. Each scenario is an optimal power flow formulation. See OPFLOW. The last equation is the coupling between the 2nd stage contingency scenarios and the first-stage. Each contingency scenario can either be single-period or multi-period. In the multi-period mode, additional data files for the load and wind generation profiles can be set via command line options. Multi-period SCOPFLOW is activated either by setting the command line option -scopflow_enable_multiperiod OR calling SCOPFLOWEnableMultiPeriod.

Depending on the mode, SCOPFLOW can either be preventive (mode = 0) or corrective (mode = 1). In the preventive mode, the PV and PQ generator real power is fixed to its corresponding base-case values. Any power offset/make-up is done by the swing bus generators. The corrective mode allows deviation of the PV and PQ generator real power from the base-case dispatch, constrained by its 30-min. ramp rate capability.

Dependency

To use this application, one must have ExaGO built with Ipopt. Even when using HiOp as the main solver, this application still uses Ipopt (to solve the base subproblem).

Usage

SCOPFLOW is executed via

mpiexec -n <N> ./scopflow <options>

where <options> are the available command line options as given in the next section.

Options

The current version has several options available for SCOPFLOW. These options can be set either through the options file options/scopflowoptions or via the command line.

Option Name	Description	Values (Default value)	Compatibility
-netfile	Name of network file in MATPOWER format	(case9mod.m)	4096 characters max.
-ctgcfile	Name of contingency list file	(case9.cont)	4096 characters max. Uses a native format for describing contingencies. See scopflow.h
-scopflow_Nc	Number of contingencies		With this option set, SCOPFLOW will only pick up the first Nc contingencies in the contingency file. To select all contingencies, use -scopflow_Nc -1
-scopflow_model	SCOPFLOW model type	GENRAMP, GENRAMPT (GENRAMP)
-scopflow_solver	Optimization solver	(Ipopt), HiOp, or EMPAR	See the note below on solvers
-scopflow_mode	Mode of operation	0 or 1 (0)	See the note below on mode of operation
-scopflow_subproblem_solver	Optimization solver for the subproblem when using HiOp solver	Ipopt or HiOp (Ipopt)	See opflow page for description of solvers
-scopflow_subproblem_model	Model for the subproblem when using HiOp solver	(POWER_BALANCE_POLAR)	See opflow page for available models
-scopflow_mode	Mode of operation	0 or 1 (0)	See the note below on mode of operation
-scopflow_tolerance	Optimization solver tolerance	(1e-6)	All solvers
-scopflow_enable_multiperiod	Include multi-period	0 or 1 (0)	Only compatible with Ipopt solver
-scopflow_duration	Duration for multi-period run in hours		Only when multi-period is enabled
-scopflow_dT	Time-step for multi-period run in minutes		Only when multi-period is enabled
-scopflow_ploadprofile	Active power load profile filename		Only when multi-period is enabled
-scopflow_qloadprofile	Reactive power load profile filename		Only when multi-period is enabled
-scopflow_windgenprofile	Wind generation profile filename		Only when multi-period is enabled
-print_output	Print SCOPFLOW solution to screen	0 or 1 (0)	All solvers
-save_output	Save OPFLOW solution to file	0 or 1 (0)	All solvers

Contingencies

Contingencies can either be specified in PTI format (.con file) or a native format. The description of the native format is given in the header file include/scopflow.h. SCOPFLOW supports single/multiple generator and line/transformer outage contingencies.

Solver

SCOPFLOW can be solved with either Ipopt, HiOp, or EMPAR. With Ipopt, SCOPFLOW can be only run on one processor (N = 1) as Ipopt only supports single process execution. HiOp supports a distributed solution allowing SCOPFLOW to be solved in parallel. It uses a two-stage primal decomposition algorithm for solving the problem.

In addition, one can solve SCOPFLOW in an embarrassingly parallel model with the EMPAR solver. With EMPAR, the base case and the contingencies are solved independently, i.e, there is no coupling.

Mode

Set SCOPFLOW to either run in preventive (0) or corrective (1) mode. In preventive mode, any power deficit or surplus in the contingency problem is provided by the swing bus only. In the corrective mode, in addition to the swing bus, the generators at PV/PQ buses contribute to the deficit/surplus. The contribution amount is decided by the optimization with the constraint that the real power dispatch for these generators should be within 30-min ramping limit.