Motivation. Preliminary Results with Transmission Switching. The solution to the DCOPF approximation is sometimes AC infeasible, and it is not easy to restore feasibility. DCOPF approximation solutions are more costly than ACOPF solutions. Transmission Switching Approaches: LP
Preliminary Results with Transmission Switching
Solving the ACOPF Problem with Transmission Switching: Linearizing the ACOPF Current-Voltage Formulation
Abstract: The solution of the optimal power flow (OPF) problem is used by large regional energy markets (RTOs and ISOs) to determine wholesale energy prices, generator dispatch, and system conditions. However, the alternating current OPF (ACOPF) is nonlinear, nonconvex, and time-consuming to solve; usually, the direct-current approximation is solved and adjusted until the solution is AC feasible. This approach uses an iterative linear approximation of the ACOPF to solve for an AC-feasible solution close to the optimal solution. The IEEE 18-, 30-, 57- and 118- bus cases are solved using this approach. This method is also extended to solve the ACOPF with transmission switching.
V&I Initial Constraints:
Approximate feasible region (blue for voltage, blue+green for current) by an outer polygon (pink+blue+green). Here, polygons of 16 and 32 sides were tested.
14 Bus, Tight Current Constraint
Results without Switching
Additional V&I Constraints:
After each iteration, add linear constraints to cut off any solutions exceeding vmaxor imax.
57 Bus, Loose Current Constraint
Approximate P&Q using a Taylor series expansion for each. To reduce the error of the approximation, progressively reduce the amount vr and vi can move from their previous values.
Solve LP Approximation
Add voltage and current cuts to cut off AC infeasible solutions
Reset fixed points in P&Q Taylor series expansions as LP optimal solutions