Stability-constrained Optimal Power Flow Model Research Articles

Preventive–corrective stability constrained OPF in microgrids for accommodating DG plug-and-play

To accommodate unpredictable plug-and-play (PnP) of distributed generators (DGs) in droop controlled microgrids, this paper proposes a preventive–corrective stability constrained optimal power flow (SC-OPF). Firstly, considering that DG droops are restricted by load sharing, we introduce the battery energy storage system (BESS) with adjustable droops, which acts as a new control resource. Secondly, we propose a bi-level optimization problem, where the upper level ensures minimizing the preventive–corrective coordinated cost and accommodating DG PnPs without violating stability constraints and the lower level focuses on the stability index given by semi-definite program (SDP) based on the Lyapunov equation. With the previously proposed analytical stability sensitivity, the lower level problem is reformulated by a series of linear constraints through the Benders decomposition method, and hence the entire bilevel problem can be solved efficiently and accurately. We apply the modified IEEE 33-bus system to validate the proposed SC-OPF model. From simulation results, the proposed model significantly improves the economic cost, stability, and computational efficiency compared to other SC-OPF models without considering BESS droop control or PnPs.

Gas-to-electricity investment planning for power system stability improvement and environmental sustainability in Nigeria

Power outage is a prominent feature of the current Nigerian power system. However, a properly planned energy sector can help the nations quest for energy sustainability and economic development. Techno-economic assessment of the Nigerian energy facilities for efficient gas-to-grid power integration is presented in this paper using the particle swarm optimization algorithm (PSO) for solving a voltage stability-constrained optimal power flow model on Matlab environment. Investment in gas-fired DG technology can be an economic and sustainable approach for reducing the detrimental effeccts of gas-flaring practices of the petroleum industries on the environment. The technical benefits such as voltage profile improvement and voltage stability enhancement are the main focus of the technical analysis carried out in this study.

Enhancements to Stability Constrained OPF to Overcome Sub-optimality

This article revisits the stability constrained optimal power flow (SOPF) model originally developed by the authors. One of the limitations of the SOPF model is that the representation of angular stability rests on assumptions that can lead to a sub-optimal dispatch outcome. The present research enhances the SOPF model to improve upon the quality of the solution. This article demonstrates that the feasible set of a stability-constrained optimal power flow problem can be open and hence the optimal solution may not exist. The article then reviews a step-by-step integration (SBSI) based approach which has the limitation of yielding sub-optimal solutions. A primary objective of the present research is to introduce two algorithms that can be used to find an improved solution, starting with a sub-optimal solution. Finally, the article also discusses several implementation issues including the concepts for dealing with multiple contingencies. Numerical examples are presented to illustrate the methodological aspects.