J.L.R. Pereira

Transmission system expansion planning using a sigmoid function to handle integer investment variables

Summary form only given. This paper presents an optimum power flow (OPF) modeling algorithm that uses the primal-dual interior point technique to determine the best investment strategy in the transmission line expansion problem. In the proposed method the expansion decision (0 or 1) is mitigated by using a sigmoid function which is incorporated in the OPF problem through the modified DC power flow equations. The investment decision is taken using a new heuristic model based on enhanced sensitivity introduced by the OPF results. Additionally the transmission power losses are considered in the network model. The proposed methodology has been compared with methods available in the literature, using both a test system and an equivalent of the southeastern Brazilian system

Redispatch to Reduce Rotor Shaft Impacts Upon Transmission Loop Closure

This paper describes a novel generation rescheduling method to reduce the generator rotor shaft impacts induced by transmission loop closures. The rotor shaft impact constraints, at the instant of transmission loop closure, are explicitly modeled into an interior point optimal power flow. This method represents a considerable improvement on the conventional redispatch for reducing the standing phase angle of the closing breaker. Optimal power flow and transient stability results are provided for a tutorial four-bus and the IEEE 118-bus test systems.

A new approach for area interchange control modeling

This paper describes a new methodology to evaluate the area interchange control (AIC) in a power flow problem using the Newton-Raphson method. In this methodology, the equations of the AIC are incorporated into the system of equations of the power flow problem. Thus an augmented system of equations, which is linearized and solved, at each iteration, is obtained. The proposed method has been tested and compared with existing methods in the literature using both small and large scale systems. The results presented validate the proposed technique.

Reducing standing phase angles via interior point optimum power flow for improved system restoration

Maximum limits for standing phase angles (SPA) must be imposed upon network loop closure, during the transmission system restoration process. These limits reduce the risk of damage in generation and transmission equipment. This paper presents an interior point optimum power flow (OPF) tool, whose objective function to be minimized is the deviation of active power generation and/or load shedding. The maximum limits of SPA are modeled as additional constraints. A practical restoration problem in one large area of the Brazilian interconnected system was analyzed and the results indicated the effectiveness of the proposed technique.

Distribution systems restoration using the Interior Point Method and sensibility analysis

This Panel Discussion proposes the development of methodologies to solve the Distribution System restoration problem, according to multiple objectives, such as to restore as much consumers as possible with minimal switching operations. This methodology uses graph theory to identify out-of-service areas and loops in the system. After that, the system switches are opened and closed based on a sensibility index, obtained from an Optimum Power Flow (OPF) algorithm using the Interior Point Method (IPM). This methodology solves the problem step-by-step, providing a feasible switching operation sequence. The results are compared with some systems presented in the literature.

Distribution system state estimation using phasor measurement units

This paper presents a new methodology to solve for the state estimation problem in radial distribution networks. The state estimation process is formulated as a constrained optimization problem in which the non-monitored loads are represented by a set of bounded inequality constraints. The branch currents in rectangular coordinates are chosen as state variables. The set of measurements considered are currents and voltages from the PMUs as well as the zero current injections at the no-load buses. The objective function to be minimized is defined as the weighted least square measurements errors. The methodology is validated through simulations on some IEEE radial test feeders.

Assessment of the generator remote voltage control through static security regions

This paper describes the use of a static security tool, based on security regions, to evaluate strategies of voltage control in power systems. The remote voltage control technique involving generators and/or synchronous compensators is used as strategy to exploit the system voltage control resources. The proposed tool has been tested using both a 9-bus tutorial system and the 39-bus New England system. The results presented validate and clearly indicate the effectiveness of the proposed method.