A Generic Approach for Solving Nonlinear-Discrete Security-Constrained Optimal Power Flow Problems in Large-Scale Systems

in IEEE Transactions on Power Systems (in press)

This paper proves the practicality of an iterative algorithm for solving realistic large-scale SCOPF problems. This algorithm is based on the combination of a contingency filtering scheme, used to ... [more ▼]

This paper proves the practicality of an iterative algorithm for solving realistic large-scale SCOPF problems. This algorithm is based on the combination of a contingency filtering scheme, used to identify the binding contingencies at the optimum, and a network compression method, used to reduce the complexity of the post-contingency models included in the SCOPF formulation. We show that by combining these two complementary ideas, it is possible to solve in a reasonable time SCOPF problems on large power system models with a large number of contingencies. Unlike most results reported for large-scale SCOPF problems, our algorithm uses a non-linear AC network model in both pre-contingency and post-contingency states, optimizes both active/reactive powers flows jointly, and treats the discrete variables. The proposed algorithm is implemented with state-of-the-art solvers and applied to two systems: a national grid with 2563 buses and 1297 contingencies, and a model of the European transmission network with 9241 buses and 12000 contingencies. [less ▲]

Assessing the Potential of Network Reconfiguration to Improve Distributed Generation Hosting Capacity in Active Distribution Systems

in IEEE Transactions on Power Systems (2014), 30(1), 346-356

As the amount of distributed generation (DG) is growing worldwide, the need to increase the hosting capacity of distribution systems without reinforcements is becoming nowadays a major concern. This paper ... [more ▼]

As the amount of distributed generation (DG) is growing worldwide, the need to increase the hosting capacity of distribution systems without reinforcements is becoming nowadays a major concern. This paper explores how the DG hosting capacity of active distribution systems can be increased by means of network reconfiguration, both static, i.e., grid reconfiguration at planning stage, and dynamic, i.e., grid reconfiguration using remotely controlled switches as an active network management (ANM) scheme. The problem is formulated as a mixed-integer, nonlinear, multi-period optimal power flow (MP-OPF) which aims to maximize the DG hosting capacity under thermal and voltage constraints. This work further proposes an algorithm to break-down the large problem size when many periods have to be considered. The effectiveness of the approach and the significant benefits obtained by static and dynamic reconfiguration options in terms of DG hosting capacity are demonstrated using a modified benchmark distribution system. [less ▲]

Contingency ranking with respect to overloads in very large power systems taking into account uncertainty, preventive and corrective actions

in IEEE Transactions on Power Systems (2013), 28(4), 4909-4017

This paper deals with day-ahead security management with respect to a postulated set of contingencies while taking into account uncertainties about the next day generation/load scenario. In order to help ... [more ▼]

This paper deals with day-ahead security management with respect to a postulated set of contingencies while taking into account uncertainties about the next day generation/load scenario. In order to help the system operator in decision making under uncertainty we aim at ranking these contingencies into four clusters according to the type of control actions needed to cover the worst uncertainty pattern of each contingency with respect to branch overload. To this end we use a fixed point algorithm that loops over two main modules: a discrete bi-level program (BLV) that computes the worst-case scenario, and a special kind of security constrained optimal power flow (SCOPF) which computes optimal preventive/corrective actions to cover the worst-case. We rely on a DC grid model, as the large number of binary variables, the large size of the problem, and the stringent computational requirements preclude the use of existing mixed integer nonlinear programming (MINLP) solvers. Consequently we solve the SCOPF using a mixed integer linear programming (MILP) solver while the BLV is decomposed into a series of MILPs. We provide numerical results with our approach on a very large European system model with 9241 buses and 5126 contingencies. [less ▲]

Overloads Management in Active Radial Distribution Systems: an Optimization Approach Including Network Switching

in 2013 IEEE PES PowerTech (2013, June)

This paper focuses on the real-time overloads management in active radial distribution systems that host a significant amount of distributed generators (DGs). In order to possibly reduce the amount of ... [more ▼]

This paper focuses on the real-time overloads management in active radial distribution systems that host a significant amount of distributed generators (DGs). In order to possibly reduce the amount of generation curtailed to remove congestion, and hence harvest as much renewable energy as possible, we propose a centralized optimization approach that includes the option to use remotely controlled grid switches and breakers so as to transfer distributed generation between feeders. To mitigate the computational burden posed by modeling the switching actions as binary variables we build upon a very convenient existing optimization framework that, for a radial distribution grid, transforms precisely the original mixed integer nonlinear programming (MINLP) problem into a much simpler mixed integer quadratically constrained (MIQC) one. Although the approach focuses on overload removal in course of optimization it also pays attention not worsening other operational constraints such as voltage limits. We prove the interest and feasibility of our approach using a 33-bus benchmark distribution system as well as a 61-bus real-life distribution system model. [less ▲]

Experiments with the interior-point method for solving large scale optimal power flow problems

in Electric Power Systems Research (2013), 95(2), 276-283

This paper reports extensive results obtained with the Interior-Point Method (IPM) for nonlinear programms (NLPs) stemming from large-scale and severly constrained classical Optimal Power Flow (OPF) and ... [more ▼]

This paper reports extensive results obtained with the Interior-Point Method (IPM) for nonlinear programms (NLPs) stemming from large-scale and severly constrained classical Optimal Power Flow (OPF) and Security-Constrained Optimal Power Flow (SCOPF) problems. The paper discusses transparently the problems encountered such as convergence reliability and speed issues of the method. [less ▲]

Computation of worst operation scenarios under uncertainty for static security management

in IEEE Transactions on Power Systems (2013), 28(2), 1697-1705

This paper deals with day-ahead static security assessment with respect to a postulated set of contingencies while taking into account uncertainties about the next day system conditions. We propose a ... [more ▼]

This paper deals with day-ahead static security assessment with respect to a postulated set of contingencies while taking into account uncertainties about the next day system conditions. We propose a heuristic approach to compute the worst-case under operation uncertainty for a contingency with respect to overloads. We formulate this problem as a non-convex nonlinear bilevel program that we solve approximately by a heuristic approach which relies on the solution of successive optimal power flow (OPF) and security-constrained optimal power flow (SCOPF) problems of a special type. The method aims at revealing those combinations of uncertainties and contingencies for which the best combination of preventive and corrective actions would not suffice to ensure security. Extensive numerical results on a small, a medium, and a very large system prove the interest of the approach. [less ▲]