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Optimal power flows play a key role in power system operation planning. While most papers in the literature focus on attaining optima, sequencing paths of optimal control adjustments that lead the system from an initial operating point towards the optimum remain scarcely accounted for. Thus, this work proposes a practical framework based upon power system steady-state analysis for sequencing strictly feasible paths of optimal control adjustments determined by the Optimal Reactive Dispatch (ORD) via Lagrange multiplier sensitivity analysis. The proposed framework is methodologically founded on the reformulation of the ORD in terms of optimal control adjustments rather than optimal control values, successive Newton’s power flow calculations to assure a strictly feasible path from the initial operating point towards the optimum, and successive resolutions of the reformulated ORD’s associated dual problem to determine Lagrange multipliers along such sequence path. Thus, pondering optimal control adjustments by their respective Lagrange multipliers indicates which control action must be realised. Numerical results for IEEE test-systems with up to 300 buses with an increased number of controllable variables are obtained to validate and illustrate the efficiency and robustness of the proposed framework.

Given the recent progresses in designing and implementing electricity market optimization-based tools to support power allocations that bridge the gap between supply and demand, the realistic modeling of optimal power flow-based auction systems provide transparent and higher transaction levels among market players, as well as more accurate locational marginal prices. Nevertheless, actual voltage stability/security representation in these auction systems remains an open question. Thus, this paper proposes a two-stage resolution framework for a nonlinear Voltage-Stability/Security-Constrained Optimal Power Flow (VSCOPF)-based auction system. The first stage of the proposed framework consists in solving a single-period two-sided VSCOPF-based auction system model by a Particle Swarm Optimization (PSO) algorithm, which adjusts active power allocations and generator voltage magnitudes while verifying if the grid's technical-operational constraints are satisfied by power flow calculations. The system voltage stability/security is addressed in the second stage by a maximal loading problem solved by the Continuation Power Flow method. Then, if a minimal voltage stability/security margin condition is not satisfied, active power allocations and generator voltage magnitudes are readjusted by the PSO to comply with stable/secure power allocations. Results with a 6-bus test-system are presented to illustrate this proposal and, therefore, show the effectiveness of proposing a two-stage resolution framework for VSCOPF-based auction systems.

The problem of voltage magnitude control, based on dispatching reactive power, consists in defining the adjustments that must be applied to synchronous generators to bring the voltages of the load buses whose magnitudes are violated within a suitable value range. The utilities usually determine the sequence of adjustments and sent to the selected control device to correct voltage magnitude violations, which makes the use of data communication technologies a necessity to enable this operation. In this context, this work proposes an application of a communication infrastructure for the control of voltage magnitude in transmission power systems. The adjustments in the voltage magnitude of control devices and the sequence of their execution are determined in the Control Manager utilizing two linear sensitivity-based methodologies and, then, transmitted via a WiMAX (Worldwide Interoperability for Microwave Access) network to Control Nodes, which in turn are connected to synchronous generators or condensers. NS-3 (Network Simulator 3) is used to simulate the 118-bus IEEE transmission test system with voltage magnitude violations. The results display an operating scenario that presents voltage violation and the applied communication infrastructure ensures that the sequence of adjustments are forwarded to the control points in order to bring the system state to the appropriate voltage magnitude ranges. The communication infrastructure WiMAX simulated in the NS-3 ensures that the sequence of adjustments are forwarded to the control points in appropriate delay and demonstrates the applicability of WiMAX technology for the control voltage magnitude. At last, to validate the proposed approach, in this paper we present the voltage magnitude in generators and load buses, as well as the availability, the delay and the volume of data transmitted by the WiMAX network as the adjustments in control variables, are executed.